Simple solar charger are small devices which allow you to charge a battery quickly and cheaply, through solar energy.
A simple solar charger must have 3 basic features built-in:
- It should be low cost.
- Layman friendly, and easy to build.
- Must be efficient enough to satisfy the fundamental battery charging needs.
The post comprehensively explains nine best yet simple solar battery charger circuits using the IC LM338, transistors, MOSFET, buck converter, etc which can be built and installed even by a layman for charging all types of batteries and operating other related equipment
Overview
Solar panels are not new to us and today it's being employed extensively in all sectors. The main property of this device to convert solar energy to electrical energy has made it very popular and now it's being strongly considered as the future solution for all electrical power crisis or shortages.
Solar energy may be used directly for powering an electrical equipment or simply stored in an appropriate storage device for later use.
Normally there's only one efficient way of storing electrical power, and it's by using rechargeable batteries.
Rechargeable batteries are probably the best and the most efficient way of collecting or storing electrical energy for later usage.
The energy from a solar cell or a solar panel can also be effectively stored so that it can be used as per ones own preference, normally after the sun has set or when it's dark and when the stored power becomes much needed for operating the lights.
Though it might look quite simple, charging a battery from a solar panel is never easy, because of two reasons:
The voltage from a solar panel can vary hugely, depending upon the incident sun rays, and
The current also varies due to the same above reasons.
The above two reason can make the charging parameters of a typical rechargeable battery very unpredictable and dangerous.
UPDATE:
Before delving into the following concepts you can probably try this super easy solar battery charger which will ensure safe and guaranteed charging of a small 12V 7 Ah battery through a small solar panel:
Parts Required
- Solar Panel - 20V, 1 amp
- IC 7812 - 1no
- 1N4007 Diodes - 3nos
- 2k2 1/4 watt resistor - 1no
That looks cool isn't it. In fact the IC and the diodes could already resting in your electronic junk box, so need of buying them. Now let's see how these can be configured for the final outcome.
As we know the IC 7812 will produce a fixed 12V at the output which cannot be used for charging a 12V battery. The 3 diodes connected at its ground (GND) terminals is introduced specifically to counter this problem, and to upgrade the IC output to about 12 + 0.7 + 0.7 + 0.7 V = 14.1 V, which is exactly what is required for charging a 12 V battery fully.
The drop of 0.7 V across each diodes raises the grounding threshold of the IC by stipulated level forcing the IC to regulate the output at 14.1 V instead of 12 V. The 2k2 resistor is used to activate or bias the diodes so that it can conduct and enforce the intended 2.1 V total drop.
1) Using LM338 as Solar Controller
But thanks to the modern highly versatile chips like the LM 338 and LM 317, which can handle the above situations very effectively, making the charging process of all rechargeable batteries through a solar panel very safe and desirable.
The circuit of a simple LM338 solar battery charger is shown below, using the IC LM338:
The circuit diagram shows a simple set up using the IC LM 338 which has been configured in its standard regulated power supply mode.
Using a Current Control Feature
The specialty of the design is that it incorporates a current control feature also.
It means that, if the current tends to increase at the input, which might normally take place when the sun ray intensity increases proportionately, the voltage of the charger drops proportionately, pulling down the current back to the specified rating.
As we can see in the diagram, the collector/emitter of the transistor BC547 is connected across the ADJ and the ground, it becomes responsible for initiating the current control actions.
As the input current rises, the battery starts drawing more current, this build up a voltage across R3 which is translated into a corresponding base drive for the transistor.
The transistor conducts and corrects the voltage via the C LM338, so that the current rate gets adjusted as per the safe requirements of the battery.
Current Limit Formula:
R3 may be calculated with the following formula
R3 = 0.7/ Max Current Limit
PCB Design for the above explained simple solar battery charger circuit is given below:
The meter and the input diode are not included in the PCB.
2) $1 Solar Battery Charger Circuit
The second design explains a cheap yet effective, less than $1 cheap yet effective solar charger circuit, which can be built even by a layman for harnessing efficient solar battery charging.
You will need just a solar panel panel, a selector switch and some diodes for getting a reasonably effective solar charger set up.
What is Maximum Power Point Solar Tracking?
For a layman this would be something too complex and sophisticated to grasp and a system involving extreme electronics.
In a way it may be true and surely MPPTs are sophisticated high end devices which are meant for optimizing the charging of the battery without altering the solar panel V/I curve.
In simple words an MPPT tracks the instantaneous maximum available voltage from the solar panel and adjusts the charging rate of the battery such that the panel voltage remains unaffected or away from loading.
Put simply, a solar panel would work most efficiently if its maximum instantaneous voltage is not dragged down close to the connected battery voltage, which is being charged.
For example, if the open circuit voltage of your solar panel is 20V and the battery to be charged is rated at 12V, and if you connect the two directly would cause the panel voltage to drop to the battery voltage, which would make things too inefficient.
Conversely if you could keep the panel voltage unaltered yet extract the best possible charging option from it, would make the system work with MPPT principle.
So it's all about charging the battery optimally without affecting or dropping the panel voltage.
There's one simple and zero cost method of implementing the above conditions.
Choose a solar panel whose open circuit voltage matches the battery charging voltage. Meaning for a 12V battery you may choose a panel with 15V and that would produce maximum optimization of both the parameters.
However practically the above conditions could be difficult to achieve because solar panels never produce constant outputs, and tend to generate deteriorating power levels in response to varying sun ray positions.
That's why always a much higher rated solar panel is recommended so that even under worse day time conditions it keeps the battery charging.
Having said that, by no means it is necessary to go for expensive MPPT systems, you can get similar results by spending a few bucks for it. The following discussion will make the procedures clear.
How the Circuit Works
As discussed above, in order to avoid unnecessary loading of the panel we need to have conditions ideally matching the PV voltage with the battery voltage.
This can be done by using a few diodes, a cheap voltmeter or your existing multimeter and a rotary switch. Ofcourse at around $1 you cannot expect it to be automatic, you may have to work with the switch quite a few times each day.
We know that a rectifier diode's forward voltage drop is around 0.6 volts, so by adding many diodes in series it can be possible to isolate the panel from getting dragged to the connected battery voltage.
Referring to the circuit digaram given below, a cool little MPPT charger can be arranged using the shown cheap components.
Let's assume in the diagram, the panel open circuit voltage to be 20V and the battery to be rated at 12V.
Connecting them directly would drag the panel voltage to the battery level making things inappropriate.
By adding 9 diodes in series we effectively isolate the panel from getting loaded and dragged to the battery voltage and yet extract the Maximum charging current from it.
The total forward drop of the combined diodes would be around 5V, plus battery charging voltage 14.4V gives around 20V, meaning once connected with all the diodes in series during peak sunshine, the panel voltage would drop marginally to may be around 19V resulting an efficient charging of the battery.
Now suppose the sun begins dipping, causing the panel voltage to drop below the rated voltage, this can be monitored across the connected voltmeter, and a few diodes skipped until the battery is restored with receiving optimal power.
The arrow symbol shown connected with the panel voltage positive can be replaced with a rotary switched for the recommended selection of the diodes in series.
With the above situation implemented, a clear MPPT charging conditions can be simulated effectively without employing costly devices. You can do this for all types of panels and batteries just by including more number of diodes in series.
3) Solar Charger and Driver Circuit for 10W/20W/30W/50W White High Power SMD LED
The 3rd idea teaches us how to build a simple solar LED with battery charger circuit for illuminating high power LED (SMD) lights in the order of 10 watt to 50 watt. The SMD LEDs are fully safeguarded thermally and from over current using an inexpensive LM 338 current limiter stage. The idea was requested by Mr. Sarfraz Ahmad.
Technical Specifications
Basically I am a certified mechanical engineer from Germany 35 years ago and worked overseas for many years and left many years ago due to personal problems back home.
Sorry to bother you but I know about your capabilities and expertise in electronics and sincerity to help and guide the beginnings like me.I have seen this circuit some where for 12 vdc.I have attached to SMD ,12v 10 watt, cap 1000uf,16 volt and a bridge rectifier you can see the part number on that.When I turn the lights on the rectifier starts to heat up and the both SMDs as well. I am afraid if these lights are left on for a long time it may damage the SMDs and rectifier. I don not know where the problem is. You may help me.
I have a light in car porch which turns on at disk and off at dawn. Unfortunately due to load shedding when there is no electricity this light remains off till the electricity is back.
I want to install at least two SMD (12 volt) with LDR so as soon the light turns off the SMD lights will turn on. I want to additional two similar light elsewhere in the car porch to keep the entire are lighted.I think that if I connect all these four SMD lights with 12 volt power supply which will get the power from UPS circuit.
Of course it will put additional load on UPS battery which is hardly fully charged due to frequent load shedding. The other best solution is to install 12 volt solar panel and attach all these four SMD lights with it. It will charge the battery and will turn the lights On/OFF.
This solar panel should be capable to keeps these lights all the night and will turn OFF at dawn.Please also help me and give details about this circuit/project.
You may take your time to figure out how to do that.I am writing to you as unfortunately no electronics or solar product seller in our local market is willing to give me any help, None of them seems to be technical qualified and they just want to sell their parts.
Sarfraz AhmadRawalpindi, Pakistan
The Design
In the shown 10 watt to 50 watt SMD solar LED light circuit with automatic charger above, we see the following stages:
- A solar panel
- A couple of current controlled LM338 regulator circuits
- A changeover relay
- A rechargeable battery
- and a 40 watt LED SMD module
The above stages are integrated in the following explained manner:
The two LM 338 stages are configured in standard current regulator modes with using the respective current sensing resistances for ensuring a current controlled output for the relevant connected load.
The load for the left LM338 is the battery which is charged from this LM338 stage and a solar panel input source. The resistor Rx is calculated such that the battery receives the stipulated amount of current and is not over driven or over charged.
The right side LM 338 is loaded with the LED module and here too the Ry makes sure that module is supplied with the correct specified amount of current in order to safeguard the devices from a thermal runaway situation.
The solar panel voltage specs may be anywhere between 18V and 24V.
A relay is introduced in the circuit and is wired with the LED module such that it's switched ON only during the night or when it's dark below threshold for the solar panel to generate the required any power.
As long as the solar voltage is available, the relay stays energized isolating the LED module from the battery and ensuring that the 40 watt LED module remains shut off during day time and while the battery is being charged.
After dusk, when the solar voltage becomes sufficiently low, the relay is no longer able to hold its N/O position and flips to the N/C changeover, connecting the battery with the LED module, and illuminating the array through the available fully charged battery power.
The LED module can be seen attached with a heatsink which must be sufficiently large in order to achieve an optimal outcome from the module and for ensuring longer life and brightness from the device.
Calculating the Resistor Values
The indicated limiting resistors may be calculated from the given formulas:
Rx = 1.25/battery charging current
Ry = 1.25/LED current rating.
Assuming the battery to be a 40 AH lead acid battery, the preferred charging current should be 4 amps.
therefore Rx = 1.25/4 = 0.31 ohms
wattage = 1.25 x 4 = 5 watts
The LED current can be found by dividing its total wattage by the voltage rating, that is 40/12 = 3.3amps
therefore Ry = 1.25/3 = 0.4 ohms
wattage = 1.25 x 3 = 3.75 watts or 4 watts.
Limiting resistors are not employed for the 10 watt LEDs since the input voltage from the battery is on par with the specified 12V limit of the LED module and therefore cannot exceed the safe limits.
The above explanation reveals how the IC LM338 can be simply used for making an useful solar LED light circuit with an automatic charger.
4) Automatic Solar Light Circuit using a Relay
In our 4rth automatic solar light circuit we incorporate a single relay as a switch for charging a battery during day time or as long as the solar panel is generating electricity, and for illuminating a connected LED while the panel is not active.
Upgrading to a Relay Changeover
In one of my previous article which explained a simple solar garden light circuit, we employed a single transistor for the switching operation.
One disadvantage of the earlier circuit is, it does not provide a regulated charging for the battery, although it not might be strictly essential since the battery is never charged to its full potential, this aspect might require an improvement.
Another associated disadvantage of the earlier circuit is its low power spec which restricts it from using high power batteries and LEDs.
The following circuit effectively solves both the above two issues, with the help of a relay and a emitter follower transistor stage.
Circuit Diagram
How it Works
During optimal sun shine, the relay gets sufficient power from the panel and remains switched ON with its N/O contacts activated.
This enables the battery to get the charging voltage through a transistor emitter follower voltage regulator.
The emitter follower design is configured using a TIP122, a resistor and a zener diode. The resistor provides the necessary biasing for the transistor to conduct, while the zener diode value clamps the emitter voltage is controlled at just below the zener voltage value.
The zener value is therefore appropriately chosen to match the charging voltage of the connected battery.
For a 6V battery the zener voltage could be selected as 7.5V, for 12V battery the zener voltage could be around 15V and so on.
The emitter follower also makes sure that the battery is never allowed to get overcharged above the allocated charging limit.
During evening, when a substantial drop in sunlight is detected, the relay is inhibited from the required minimum holding voltage, causing it to shift from its N/O to N/C contact.
The above relay changeover instantly reverts the battery from charging mode to the LED mode, illuminating the LED through the battery voltage.
Parts list for a 6V/4AH automatic solar light circuit using a relay changeover
- Solar Panel = 9V, 1amp
- Relay = 6V/200mA
- Rx = 10 ohm/2 watt
- zener diode = 7.5V, 1/2 watt
5) Transistorized Solar Charger Controller Circuit
The fifth idea presented below details a simple solar charger circuit with automatic cut-off using transistors only. The idea was requested by Mr. Mubarak Idris.
Circuit Objectives and Requirements
- Please sir can you make me a 12v, 28.8AH lithium ion battery,automatic charge controller using solar panel as a supply, which is 17v at 4.5A at max sun light.
- The charge controller should be able to have over charge protection and low battery cut off and the circuit should be simple to do for beginner without ic or micro controller.
- The circuit should use relay or bjt transistors as a switch and zener for voltage reference thanks sir hope to hear from you soon!
The Design
PCB Design
Referring to the above simple solar charger circuit using transistors, the automatic cut off for the full charge charge level and the lower level is done through a couple of BJTs configured as comparators.
Recall the earlier low battery indicator circuit using transistors, where the low battery level was indicated using just two transistors and a few other passive components.
Here we employ an identical design for the sensing of the battery levels and for enforcing the required switching of the battery across the solar panel and the connected load.
Let's assume initially we have a partially discharged battery which causes the first BC547 from left to stop conducting (this is set by adjusting the base preset to this threshold limit), and allows the next BC547 to conduct.
When this BC547 conducts it enable the TIP127 to switch ON, which in turn allows the solar panel voltage to reach the battery and begin charging it.
The above situation conversely keeps the TIP122 switched OFF so that the load is unable to operate.
As the battery begins getting charged, the voltage across the supply rails also begin rising until a point where the left side BC547 is just able to conduct, causing the right side BC547 to stop conducting any further.
As soon as this happens, the TIP127 is inhibited from the negative base signals and it gradually stops conducting such that the battery gradually gets cut off from the solar panel voltage.
However, the above situation permits the TIP122 to slowly receive a base biasing trigger and it begins conducting....which ensures that the load now is able to get the required supply for its operations.
The above explained solar charger circuit using transistors and with auto cut-offs can be used for any small scale solar controller applications such as for charging cellphone batteries or other forms of Li-ion batteries safely.
For getting a Regulated Charging Supply
The following design shows how to convert or upgrade the above circuit diagram into a regulated charger, so that the battery is supplied with a fixed and a stabilized output regardless of a rising voltage from the solar panel.
6) Solar Pocket LED Light Circuit
The sixth design here explains a simple low cost solar pocket LED light circuit which could be used by the needy and, underprivileged section of the society for illuminating their houses at night cheaply.
The idea was requested by Mr. R.K. Rao
Circuit Objectives and Requirements
- I want to make a SOLAR pocket LED light using a 9cm x 5cm x 3cm transparent plastic box [available in the market for Rs.3/-] using a one watt LED/20mA LEDS powered by a 4v 1A rechargeable sealed lead-acid battery [SUNCA/VICTARI] & also with a provision for charging with a cell phone charger [where grid current is available].
- The battery should be replaceable when dead after use for 2/3 years/prescribed life by the rural/tribal user.
- This is meant for use by tribal/rural children to light up a book; there are better led lights in the market for around Rs.500 [d.light],for Rs.200 [Thrive].
- These lights are good except that they have a mini solar panel and a bright LED with a life of ten years if not more ,but with a rechargeable battery without a provision for its replacement when dead after two or three years of use.It is a waste of resource and unethical.
- The project i am envisaging is one in which the battery can be replaced , be locally available at low cost. The price of the light should not exceed Rs.100/150.
- It will be marketed on not for profit basis through NGOs in tribal areas and ultimately supply kits to tribal/rural youth to make them in the village.
- I along with a colleague have made some lights with 7V EW high power batteries and 2x20mA pirahna Leds and tested them-they lasted for over 30 hours of continuous lighting adequate to light up a book from half-meter distance; and another with a 4v sunce battery and 1watt 350A LED giving enough light for cooking in a hut.
- Can you suggest a circuit with a one AA/AAA rechargeable battery,mini solar panel to fit on the box cover of 9x5cm and a DC-DC booster and 20mA leds. If you want me to come over to your place for discussions i can.
- You can see the lights we have made in google photos at https://goo.gl/photos/QyYU1v5Kaag8T1WWA Thanking you,
The Design
As per the request the solar pocket LED light circuits needs to be compact, work with a single 1.5AAA cell using a DC-DC converter and equipped with a self regulating solar charger circuit.
The circuit diagram shown below probably satisfies all the above specifications and yet stays within the affordable limit.
Circuit Diagram
The design is a basic joule thief circuit using a single penlight cell, a BJT and an inductor for powering any standard 3.3V LED.
In the design a 1 watt LeD is shown although a smaller 30mA high bright LED could be used.
The solar LED circuit is capable squeezing out the last drop of "joule" or the charge from the cell and hence the name joule thief, which also implies that the LED would keep illuminated until there's virtually nothing left inside the cell. However the cell here being a rechargeable type is not recommended to be discharged below 1V.
The 1.5V battery charger in the design is built using another low power BJT configured in its emitter follower configuration, which allows it to produce an emitter voltage output that's exactly equal to the potential at its base, set by the 1K preset. This must be precisely set such that the emitter produces not more than 1.8V with a DC input of above 3V.
The DC input source is a solar panel which may be capable of producing an excess of 3V during optimal sunlight, and allow the charger to charge the battery with a maximum of 1.8V output.
Once this level is reached the emitter follower simply inhibits any further charging of the cell thus preventing any possibility of an over charge.
The inductor for the pocket solar LED light circuit consists of a small ferrite ring transformer having 20:20 turns which could be appropriately altered and optimized for enabling the most favorable voltage for the connected LED which may last even until the voltage has fallen below 1.2V.
7) Simple Solar Charger for Street Lights
The seventh solar charger discussed here is best suited as a solar LED street light system is specifically designed for the new hobbyist who can build it simply by referring to the pictorial schematic presented here.
Due to its straightforward and relatively cheaper design the system can be suitably used for village street lighting or in other similar remote areas, nonetheless this by no means restricts it from being used in cities also.
Main Features of this system are:
1) Voltage controlled Charging
2) Current Controlled LED Operation
3) No Relays used, all Solid-State Design
4) Low Critical Voltage Load Cut-off
5) Low Voltage and Critical Voltage Indicators
6) Full Charge cut-off is not included for simplicity sake and because the charging is restricted to a controlled level which will never allow the battery to over-charge.
7) Use of popular ICs like LM338 and transistors like BC547 ensure hassle free procurement
8) Day night sensing stage ensuring automatic switch OFF at dusk and switch ON at dawn.
The entire circuit design of the proposed simple LED street light system is illustrated below:
Circuit Diagram
The circuit stage comprising T1, T2, and P1 are configured into a simple low battery sensor, indicator circuit
An exactly identical stage can also be seen just below, using T3, T4 and the associated parts, which form another low voltage detector stage.
The T1, T2 stage detects the battery voltage when it drops to 13V by illuminating the attached LED at the collector of T2, while the T3, T4 stage detects the battery voltage when it reaches below 11V, and indicates the situation by illuminating the LED associated with the collector of T4.
P1 is used for adjusting the T1/T2 stage such that the T2 LED just illuminates at 12V, similarly P2 is adjusted to make the T4 LED begin illuminating at voltages below 11V.
IC1 LM338 is configured as a simple regulated voltage power supply for regulating the solar panel voltage to a precise 14V, this is done by adjusting the preset P3 appropriately.
This output from IC1 is used for charging the street lamp battery during day time and peak sunshine.
IC2 is another LM338 IC, wired in a current controller mode, its input pin is connected with the battery positive while the output is connected with the LED module.
IC2 restricts the current level from the battery and supplies the right amount of current to the LED module so that it is able operate safely during night time back up mode.
T5 is a power transistor which acts like a switch and is triggered by the critical low battery stage, whenever the battery voltage tends to reach the critical level.
Whenever this happens the base of T5 is instantly grounded by T4, shutting it off instantly. With T5 shut off, the LED module is enable to illuminate and therefore it is also shut off.
This condition prevents and safeguards the battery from getting overly discharged and damaged. In such situations the battery might need an external charging from mains using a 24V, power supply applied across the solar panel supply lines, across the cathode of D1 and ground.
The current from this supply could be specified at around 20% of battery AH, and the battery may be charged until both the LEDs stop glowing.
The T6 transistor along with its base resistors is positioned to detect the supply from the solar panel and ensure that the LED module remains disabled as long as a reasonable amount of supply is available from the panel, or in other words T6 keeps the LED module shut off until its dark enough for the LED module and then is switched ON. The opposite happen at dawn when the LED module is automatically switched OFF. R12, R13 should be carefully adjusted or selected to determine the desired thresholds for the LED module's ON/OFF cycles
How to Build
To complete this simple street light system successfully, the explained stages must be built separately and verified separately before integrating them together.
First assemble the T1, T2 stage along with R1, R2, R3, R4, P1 and the LED.
Next, using a variable power supply, apply a precise 13V to this T1, T2 stage, and adjust P1 such that the LED just illuminates, increase the supply a bit to say 13.5V and the LED should shut off. This test will confirm the correct working of this low voltage indicator stage.
Identically make the T3/T4 stage and set P2 in a similar fashion to enable the LED to glow at 11V which becomes the critical level setting for the stage.
After this you can go ahead with the IC1 stage, and adjust the voltage across its "body" and ground to 14V by adjusting P3 to the correct extent. This should be again done by feeding a 20V or 24V supply across its input pin and ground line.
The IC2 stage can be built as shown and will not require any setting up procedure except the selection of R11 which may be done using the formula as expressed in this universal current limiter article
Parts List
- R1, R2, R3 R4, R5, R6, R7 R8, R9, R12 = 10k, 1/4 WATT
- P1, P2, P3 = 10K PRESETS
- R10 = 240 OHMS 1/4 WATT
- R13 = 22K
- D1, D3 = 6A4 DIODE
- D2, D4 = 1N4007
- T1, T2, T3, T4 = BC547
- T5 = TIP142
- R11 = SEE TEXT
- IC1, IC2 = LM338 IC TO3 package
- LED Module = Made by connecting 24nos 1 WATT LEDs in series and parallel connections
- Battery = 12V SMF, 40 AH
- Solar Panel = 20/24V, 7 Amp
Making th 24 watt LED Module
The 24 watt LED module for the above simple solar street light system could be built simply by joining 24 nos 1 watt LEDs as shown in the following image:
8) Solar Panel Buck Converter Circuit with Over Load Protection
The 8th solar concept discussed below talks about a simple solar panel buck converter circuit which can be used to obtain any desired low bucked voltage from 40 to 60V inputs. The circuit ensures a very efficient voltage conversions. The idea was requested by Mr. Deepak.
Technical Specifications
I am looking for DC - DC buck converter with following features.
1. Input voltage = 40 to 60 VDC
2. Output voltage = Regulated 12, 18 and 24 VDC (multiple output from the same circuit is not required. Separate circuit for each o/p voltage is also fine)
3. Output current capacity = 5-10A
4. Protection at output = Over current, short circuits etc.
5. Small LED indicator for unit operation would be an advantage.
Appreciate if you could help me designing the circuit.
Best regards,
Deepak
The Design
The proposed 60V to 12V, 24V buck converter circuit is shown in the figure below, the details may be understood as explained below:
The configuration could be divided into stages, viz. the astable multivibrator stage and the mosfet controlled buck converter stage.
BJT T1, T2 along with its associated parts forms a standard AMV circuit wired to generate a frequency at the rate of about 20 to 50kHz.
Mosfet Q1 along with L1 and D1 forms a standard buck converter topology for implementing the required buck voltage across C4.
The AMV is operated by the input 40V and the generated frequency is fed to the gate of the attached mosfet which instantly begins oscillating at the available current from the input driving L1, D1 network.
The above action generates the required bucked voltage across C4,
D2 makes sure that this voltage never exceeds the rated mark which may be fixed 30V.
This 30V max limit bucked voltage is further fed to a LM396 voltage regulator which may be set for getting the final desired voltage at the output at the rate of 10amps maximum.
The output may be used for charging the intended battery.
Circuit Diagram
Parts List for the above 60V input, 12V, 24V output buck converter solar for the panels.
- R1---R5 = 10K
- R6 = 240 OHMS
- R7 = 10K POT
- C1, C2 = 2nF
- C3 = 100uF/100V
- C4 = 100uF/50V
- Q1 = ANY 100V, 20AMP P-channel MOSFET
- T1,T2 = BC546
- D1 = ANY 10AMP FAST RECOVERY DIODE
- D2 = 30V ZENER 1 WATT
- D3 = 1N4007
- L1 = 30 turns of 21 SWG super enameled copper wire wound over a 10mm dia ferrite rod.
9) Home Solar Electricity Set up for an Off-the-grid Living
The ninth unique design explained here illustrates a simple calculated configuration which may be used for implementing any desired sized solar panel electricity set up for remotely located houses or for achieving an off the grid electricity system from solar panels.
Technical Specifications
I am very sure you must have this kind of circuit diagram ready. While going through your blog I got lost and could not really choose one best fitting to my requirements.
I am just trying to put my requirement here and make sure I understood it correctly.
(This is a pilot project for me to venture into this field. You can count me to be a big zero in electrical knowledge. )
My basic goal is to maximize use of Solar power and reduce my electrical bill to minimum. ( 🙁 I stay at Thane. So, you can imagine electricity bills. ) So you can consider as if I am completely making a solar powered lighting system for my home.
1. Whenever there is enough sunlight, I do not need any artificial light.2. Whenever intensity of sunlight drops below acceptable norms, I wish my lights will turn on automatically.
I would like to switch them off during bedtime, though.3. My current lighting system (which I wish to illuminate) consists of two regular bright light Tube lights ( 36W/880 8000K ) and four 8W CFLs.
Would like to replicate the whole setup with Solar-powered LED based lighting.
As I said, I am a big zero in field of electricity. So, please help me with the expected setup cost also.
The Design
36 watts x 2 plus 8 watt gives a total of around 80 watts which is the total required consumption level here.
Now since the lights are specified to work at mains voltage levels which is 220 V in India, an inverter becomes necessary for converting the solar panel voltage to the required specs for the lights to illuminate.
Also since the inverter needs a battery to operate which can be assumed to be a 12 V battery, all the parameters essential for the set up may be calculated in the following manner:
Total intended consumption is = 80 watts.
The above power may be consumed from 6 am to 6 pm which becomes the maximum period one can estimate, and that's approximately 12 hours.
Multiplying 80 by 12 gives = 960 watt hour.
It implies that the solar panel will need to produce this much watt hour for the desired period of 12 hours during the entire day.
However since we don't expect to receive optimum sunlight through the year, we can assume the average period of optimum daylight to be around 8 hours.
Dividing 960 by 8 gives = 120 watts, meaning the required solar panel will need to be at least 120 watt rated.
If the panel voltage is selected to be around 18 V, the current specs would be 120/18 = 6.66 amps or simply 7 amps.
Now let's calculate the battery size which may be employed for the inverter and which may be required to be charged with the above solar panel.
Again since the total watt hour fr the entire day is calculated to be around 960 watts, dividing this with the battery voltage (which is assumed to be 12 V) we get 960/12 = 80, that's around 80 or simply 100 AH, therefore the required battery needs to be rated at 12 V, 100 AH for getting an an optimal performance throughout the day (12 hours period).
We'll also need a solar charge controller for charging the battery, and since the battery would be charged for the period of around 8 hours, the charging rate will need to be around 8% of the rated AH, that amounts to 80 x 8% = 6.4 amps, therefore the charge controller will need to be specified to handle at least 7 amp comfortably for the required safe charging of the battery.
That concludes the entire solar panel, battery, inverter calculations which could be successfully implemented for any similar kind of set up intended for an off the grid living purpose in rural areas or other remote area.
For other V, I specs, the figures may be changed in the above explained calculation for achieving the appropriate results.
In case the battery is felt unnecessary and the solar panel could also be directly used for operating inverter.
A simple solar panel voltage regulator circuit may be witnessed in the following diagram, the given switch may be used for selecting a battery charging option or directly driving the inverter through the panel.
In the above case, the regulator needs to produce around 7 to 10amps of current therefore an LM396 or LM196 must be used in the charger stage.
The above solar panel regulator may be configured with the following simple inverter circuit which will be quite adequate for powering the requested lamps through the connected solar panel or the battery.
Parts list for the above inverter circuit: R1, R2 = 100 ohm, 10 watt
R3, R4 = 15 ohm 10 watt
T1, T2 = TIP35 on heatsinks
The last line in the request suggests an LED version to be designed for replacing and upgrading the existing CFL fluorescent lamps. The same may be implemented by simply eliminating the battery and the inverter and integrating the LEDs with the solar regulator output, as shown below:
The negative of the adapter must be connected and made common with the negative of the solar panel
Final Thoughts
So friends these were 9 basic solar battery charger designs, which were hand picked from this website.
You will find many more such enhanced solar based designs in the blog for further reading. And yes, if you have any additional idea you may definitely submit it to me, I'll make sure to introduce it here for the reading pleasure of our viewers.
Feedback from one of the Avid Readers
Hi Swagatam,
I have come across your site and find your work very inspiring. I am currently working on a Science, Technology, Engineering and Math (STEM) program for year 4-5 students in Australia. The project focuses on increasing children’s curiosity about science and how it connects to real-world applications.
The program also introduces empathy in the engineering design process where young learners are introduced to a real project (context) and engages with their fellow school peers to solve a worldly problem. For the next three years, our focus is on introducing children to the science behind electricity and the real-world application of electrical engineering. An introduction to how engineers solve real-world problems for the greater good of society.
I am currently working on online content for the program, which will focus on young learners(Grade 4-6) learning the basics of electricity, in particular, renewable energy, i.e. solar in this instance. Through a self-directed learning program, children learn and explore about electricity and energy, as they are introduced to a real-world project, i.e. providing lighting to children sheltered in the refugee camps around the world. On completion of a five-week program, children are grouped in teams to construct solar lights, which are then sent to the disadvantaged children around the world.
As a not 4 profit educational foundation we are seeking your assistance to layout a simple circuit diagram, which could be used for the construction of a 1 watt solar light as practical activity in class. We have also procured 800 solar light kits from a manufacturer, which the children will assemble, however, we need someone to simplify the circuit diagram of these light kits, which will be used for simple lessons on electricity, circuits, and calculation of power, volts, current and conversion of solar energy to electrical energy.
I look forward to hearing from you and keep on with your inspiring work.
Solving the Request
I appreciate your interest and your sincerely efforts to enlighten the new generation regarding solar energy.
I have attached the most simple yet efficient LED driver circuit which can be used for illuminating a 1 watt LED from a solar panel safely with minimum parts.
Make sure to attach a heatsink on the LED, otherwise it may burn quickly due to overheating.
The circuit is voltage controlled and current controlled for ensuring optimum safety to the LED.
Let me know if you have any further doubts.
How are you? Please, which controller circuit, do you recommend me to use two panels, 305w each,
connected in parallel, using also 3 12v batteries in parallel? Open circuit voltage (Voc): 39.9V
Peak Voltage (Vmpp): 32.7V
Short-circuit current (Isc): 9.91A
Peak Current (Impp): 9.33A. Thank you.
Hi, how are you! I think you must connect the batteries in series, not in parallel….if your batteries are 100 Ah rated then you will not need any regulator. Simply put them in series and connect directly with the 35 V panel output. With 100 Ah battery you ca even connect 2 in series without any regulator.
Actually 3 in series will require 43V…so connect two in series with 32 to 36 V input. To ensure that the full charge level does not exceed 30 V, you can add a LM338 regulator, using two LM338 in parallel.
https://homemade-circuits.com/wp-content/uploads/2012/04/LM338basicadjustablepowersupplycircuitdiagram-1.png
You can also replace the LM338 with a single LM396
How are you? And if I connect the two panels, also in series, it would be close to 65v and 9.91 Ap, connecting the 3 12v batteries in series. Could it work, not needing a controller? And what makes batteries warm? Thank you.
Yes that’s possible. but you will have to restrict the output to 14 x 3 = 42V. If the charging current is high over 20% of the Ah rating of the lead acid battery then the battery may start getting warmer, will also depend on the ambient temperature of the atmosphere.
Dear Swagatam,
Thanks for all the knowledge you are sharing though this site. I am looking to charge Li-Ion through Solar. In principle, can I use any 780X voltage regulator to feed my Li-Ion charge controller (Ex. TP4056)
Solar Panel => 780X Regulator => TP4056
Dear Chandra, yes you can use a 7805 or 7806 IC at the input
Halo, I find your article very helpful. However, I have a 100w solar panel with broken glass.it gives me voltage lower than 12v.what can I do to increase its voltage output since I don’t have money to buy a new solar
panel
Glad you liked it, however I am sorry I have no idea how to repair a solar panel with broken glass.
Thank you Sir. you have removed my all problems. As I am new to electronics I want to know from you regarding schottky diode. you are correct that you did not use this diode in your circuit but I want some information of this diode and by which diode it can be replaced. As you have mentioned earlier in your reply to me that if 0.7 volt drop is acceptable to me than I can replace with 4007 diode.
Hello AK Goel, a schottky diode is also a rectifier diode but it is designed to drop not more than 0.2 V across itself, whereas any other ordinary rectifier diode may drop anywhere around 0.5 V to 0.7 V. The second major difference is the switching speed, which is very high for schottky diodes compared to ordinary rectifier.
Thank you Sir. You have well explained to me regarding the schottky diode. You have explained it in a very simple way.
Now I am attaching a solar operated garden light which on after the sun set and off after the sun come back. This circuit is working fine but I have a problem which as under.
(1) there is no preset added in the circuit to vary the level of darkness at which the led
should on. Please tell which value of preset and where it should be added in the
circuit.
(2) How I can cut of the charging of cell 18650 used in the circuit, at 4.1 volt. Please tell
the cut off charging circuit and where it should be added in the attached circuit.
(3) I have a solar panel of 6 volt 100mah (70X70X3). can this solar panel can charge the
cell 18650 and if yes than how much time this solar panel will take to charge the cell
18650 2100mah.
Though it is not of your circuit even than I will request you to solve my problems like before and help me like a teacher. I will be highly obliged.
As there is no provision here to attach a circuit, I will send you through my email
Thank you AK Goel, 1) to control the darkness level, you can put a 10K preset between base and ground of the left side transistor in your diagram.
2) for auto cut off you can apply the following circuit
https://www.homemade-circuits.com/usb-automatic-li-ion-battery-charger/
3) 100mAh will not charge a 18650 cell properly, and may take many hours or days to charge it fully. The panel current rating must be at least 600 mA to 1 amp
Thank you Sir. You have solved my all problems. it is really wonderful that I got such a great teacher like. Thanks again
No Problem Dear AK Goel, you are welcome!
I have a solar cell operated fountain which works on 4.5v dc. The solar cell gives 6v. Now I want to ad cell 18650 so that when there is no sunshine, the fountain can still work. Please send me a circuit diagram showing the cell 18650 should be charged with solar cell in the sunshine and fountain switched off and when there is no sunshine then I can use the fountain with cell 18650.
After full charging of the 18650, the charging voltage should stop. Please send the circuit at my email addres or whatsapp no or tell me where I should see my required circuit. email id
akg1942@yahoo.com whatsapp No 9983937410, 8769044038
you can try the following circuit:
Adjust the 10k preset to get exactrly 4.2V at the output, the charging will stops as soon as this level is reached.
Dear and respected Mr SWAG. I am surprised to see that how quickly you not only replied me but You also sent the super simple trailer made circuit as per my requirement. Thank you very much SIR. This the first time I received a help so quickly that I can not imagine and secondly I found you who are very cooperative and helpful. I am a electronic hobbyist and some time I failed to make a circuit due to printing error or not properly explained of the circuit. But I am happy now that I found you and now I am sure that I will make the circuit successfully with your help if I am stuck. Now I have some more information regarding the circuit diagram you sent to me.
(1) Please give alternative transistor No for TIP 122
(2) Why Ic 7809 is used where as the solar cell with me gives only 6v. Can we stop the
charging of cell 18650 at 4v or 4.2v by using 6v solar panel only and removing IC
7809
(3) What is value of R 1 and D2
(4) In the circuit it has not been shown that where I should I connect my fountain.
Thank you dear AK Goel,
the IC 7809 is used so that the output from the TIP122 stays constant at 4.2V. If the solar panel is directly connected without IC 7809 then the output will not be fixed unless a zener diode is used in place of the preset. But precise zener diode values are not available so zener option cannot be utilized.
If you want to use a 6 V solar panel directly for charging the Li-Ion cell with precise cut off at 4.2V or 4.1V, then you can perhaps apply a shunt regulator circuit as given below:
You will have to set up the circuit by applying a 6 V / 500mA from any rectified transformer supply, and adjust the 1k preset to get a precise 4.1V at the output side. Once this is fixed you can use it for the intended purpose
Thank you Sir for your quick reply. I was waiting for your reply to solve my problems. Your first circuit using ic 7809 is good and simple I will go for that. But you have not replied my other queries just as
(1) The alternative Tr no in place of TIP 122 as it is not available. Please give some
commonly available Tr. No. which can work in place of TIP122
(2) What is the value of R1 and D2
(3) Where at what point my fountain is to be connected in the circuit.
Dear AK Goel, if you use the 7809 circuit then the solar panel will need to be 12 V rated which can be a lot costlier.
However, it may be possible to replace the 7809 with 7806 IC and use a 9V solar panel.
There’s no replacement for TIP122, but you can build an equivalent using a 2N2222 and TIP31 in Darlington pair.
You can exclude R1 if the output voltage is adjusted to 4.1 V precisely, and use a solar panel having no more than 1 amp current.
D1 can be replaced with an ON/OFf switch so that output load can be switched ON/OFF depending on the sun light conditions. This output load could be your fountain
Dear Sir. I again thanks for your detailed reply regarding my problems. I tried but could not get TIP 122 and TIP 31 as where I am living is not well connected to the electronic market.
Please Sir can you design this circuit without using this TIP 122. Please design the circuit using commonly available transistor.
Secondly i want to know that how can I replace the SCHOTTKY DIODE. Can I use other
normal diode like 4007.
Dear AK Goel, you can connect any 1 amp to 3 amp rated NPN transistor, for example BD139. Preferably use two of them in Darlington mode.
Sorry I cannot see any schotky diode in my diagram. In general a schotky diode cannot be replaced with a rectifier diode, unless a drop of 0.7 V is acceptable to you from the 1N4007…
Good day Swag, please what are your advice for longevity using automotive battery for inverter, I know deep cycle are for inverter but cost too high. Please help out
Adeyemi, by longevity I guess you mean a longer battery life. It can be achieved by maintaining correct charging/discharging rates and maintaining proper battery fluids.
More info can be founds here
https://www.homemade-circuits.com/high-current-10-to-20-amp-automatic/
I want to run all my DC appliance directly from solar panel what type of circuit I have to use. please send me the circuit diagram
It will depend on the voltage specification of the appliances.
Thank you sir. Please tell steps of regulation.
Hi sankar, It is already explained in the above article, using LM338 or 7812.
Can I run DC fan , DC LED light directly from solar panel?
yes, but after appropriate regulation
good afternoon sir please can i connect three 7812ic chargers to a single 20w solar panel
Yes you can, as long as the max voltage of the panel is within 35V
Good day sir please is there a way the Imhotep free energy relay charger can be modified to charge a battery efficiently
Hi Abraham, first we need to verify whether the energy is really a free energy or acquired from the source itself? Because the coil will store energy from the source, so it cannot be a free energy.
Sir please can the 7ah solar charger using 7812ic charge 4 7ah batteries simultaneously
Yes you can, by adding 3 more 7812 ICs in parallel, just make sure to put them on a common heatsink.
hello sir, is about the second circuit that uses FSD ammeter for monitoring when battery is fully charged. my question is
1. can’t one use one of your circuit which is low battery indicator circuit that uses ic 741 in place of FSD ammeter.
2.if l’m using 12v 75ah battery upward what will be the specification of solar pannel to be use .
3. is solar pannel rated in amps or in watts.
4. according to ur caculation for R3 which is 0.7/ charging current
0.7/75ah= 0.00933 pls correct me if my calculation are wrong
5. how can one use the 10k preset to set the circuit.
waiting for your respond
Hello young king,
you can configure it as per the first circuit from this article:
https://www.homemade-circuits.com/make-6v-4ah-automatic-battery-charger/
Just set the preset for 14V and 11V cut off thrsholds.
LM338 will not support 10 amp.
You will have to use an LM196 IC instead.
solar panel is just like any other power supply source and will be rated in amps, voltage and watts.
75 ah is the charge/discharge rate, not the current.
for 75Ah battery you can use 10 amp charge/discharge current…therfeore R3 will be = 0.7 / 10 = 0.07 ohms
setting up procedures is already explained in the relevant article.
Please how can the circuit#2 be achieved automatically
If you set the output to 14V for a 12V battery, you won’t require an auto cut-off, and battery will be safe but slightly undercharged which is very good for the battery.
i am very happy with all these projects. what i need now is a simple way to construct my own solar panel,the simplest way pls. thank you
It would be better to buy a solar panel than to construct one.
Thanks for the quick answers. You are always well disposed. May God always enlighten you. The calculation of amperage: I = P / V. Lithium batteries should be charged with 1/10Ah. Right? Assuming that the solar panel at maximum produces 6V / 1W = 0.1666Ah. In 5 hours of sunshine would I charge an 800mAh battery? Could I be able to charge a cell phone with a step up module? In the case of battery charger and lighting LEDs, could a Joule Thief be used?
Li-Ion batt can be charged at full 1C rate meaning a current that may be equal to its Ah value, but this may heat up the battery and we may require temperature controller also…so the safe value can be 0.5C or Ah/2. At 160mA the 800mAh cell may require 4 to 6 hours of charging.
A smartphone will most probably not get charged with a 6V 1watt panel
Sir Swagan could guide me on two circuits?
The first would be using a 6V./ 1W solar panel. for simple smartphone charger.
The second would be with the same solar panel, but to charge 3.7V lithium batteries. with 4 high brightness LEDs. For lighting with this same battery.
Thank you very much in advance
Marcelo,
1 watt will not charge a smartphone at 6V. Your panel must be at least 1 amp x 6 V = 6 watts.
You can use the 1 watt panel to charge 3.7 v cells but it may take many days for them to get charged fully. LEDs current must not be more than 200mA for longer back ups.
Good day Swag, please how can I modify circuit #8 to have output voltage of 36v.
Hi Blessing, what is your panel voltage and current specs… please provide all the necessary specifications, I will try to help!
Maximum solar voltage 54.6v max current 6.4amps
yes, you can use it for the mentioned application…
Please sir, any modifications.
Many modifications may be required because the coil data is not verified. I can’t suggest much because I haven’t tested it practically, but the concept is correct. Alternatively you can try the following design which is a tested one:
https://www.homemade-circuits.com/5v-pwm-solar-battery-charger-circuit/
Hello Swag, please how can I charge a 100ah and 7ah batteries with same 150w panel.the 7ah will be for emergence lighting. Thanks
What is the V and I rating of the panel?
V-19.5
I-7.65
you will need a 14V/10amp buck converter for 100 Ah battery, 7 Ah can be directly charged through a LM338 charger as explained in the above article.
Can the two chargers be linked to the 1 panel
yes no problems.
Hello Sir. Can you provide a modified circuit of this so that it can be serve both a power source will the battery is charging and the battery as power source when the solar panel is not supplying power? Thank you.
Andre, you can use the first design from the following article:
https://www.homemade-circuits.com/solar-charger-circuit-using-transistors/
Does this cut off the charging process when the battery is full? It is not Simple afterall.
If you keep the full charge voltage level from the IC slightly lower than the actual value, then the cut-off action won’t be necessary and can be ignored
Sir
Can you just clarify. Using potentiometer P1, i set the output at 14V as measured by an ordinary multimeter. But when i connect a battery that voltage drops to 11.5 V. I am expecting the voltage reading to be maintained at 14V even when the battery is connected. Can you please help explain.
Thanks very much.
Pyke
Pyke, that is perfectly alright. As soon as you connect the battery the 14V must sink to the battery’s discharge level, and slowly as the battery charges the level would be seen slowly climbing until finally the 14V is reached…and then you can assume the battery to be fully charged, and disconnect it from the supply
To implement the above procedure we always make sure that the charging current is significantly lower than the battery’s Ah rating….
Thank you very much sir. I appreciate very much you prompt and informative response. Keep up the good work. I salute you
Pyke
you are most welcome Pyke!
Sir I have to charge 24v 14ah battery by solar panel I have two 12v 20w solar panel can I charge the battery by them if I can what is the circuit
Sharath, put the panels in series and check if the output is around 29V at peak sunshine, if yes then you can charge the battery reasonably well with those panels.
I read somewhere that the float voltage for lead acid battery is around 13.8 volts, and that with this voltage, the battery could be charged as long as possible, without causing any damage to the battery. What is your take on that sir?
that is correct!
Sir,
Please find below the link to my you tube video:
https://youtu.be/Hmjy6bfFXkQ
Please tell me what you think of it.
Once again thanks for your prompt help.
That looks great Vishwa! Thanks for posting
Sir,
Thanks for your valuable and kind appreciation.
Sir,
Thanks a million for your prompt help. May I use the schematic in my youtube video. I will mention the source and link to your website.
Thanking you for your time,
You are welcome Vishwa, you can use my circuit diagram in your youtube video with a reference to my site, let me know when you have posted it.
Sir,
As I am new to electronics I have listed steps to be doubly sure of the connection:
1. Positive of solar panel to positive of D1.
2. Negative of D1 to pin 3(IN) of LM338.
3. Pin 2(OUT) of LM338 to positive of D2.
4. Negative of D2 to positive of battery.
5. Pin2(OUT) of LM338 to top terminal of R1.
6. Pin 1(ADJ) of LM338 to pin 1 of BC547.
7 Pin 1(ADJ) of LM338 to bottom terminal of R1.
8. Pin 1(ADJ) of LM338 to base of P1.
9.Pin 1(ADJ) of LM338 to top terminal of P1.
10.Pin 2 (base) of BC547 to bottom terminal of P1.
11.Pin 2 (base) of BC547 to top terminal of R3. .
12. Negative of solar panel to pin 3(emitter) of BC547.
13 Pin 3(emitter) of BC547 to bottom terminal of R3.
14. Pin 2(base) of BC547, bottom terminal of P1 and top terminal of R3 to negative terminal of battery.
Thanks for your help.
.
Vishwa, sorry I can’t verify this because I am not sure which pins of BC547 you are referring by saying pin#1, 2 etc.
It is better if you could refer to the datasheets of the respective devices and check the pinouts yourself and then connect them by comparing with the diagram
Sir,
Thanks for your prompt reply. In my question I have mentioned the pin numbers as per the datasheet of BC547.
Thanking you for your time please.
OK, then everything is fine.
How much cost to make the circuit
Sir,
I want to charge a small Li ion 3.7V 2100 mh battery using 10W solar panel with following spec.Voc 10.43V, ISc 0.90A, Vmp 8.95V, Imp 0.82A. Will it work?
Parts used:
LM337
BC547
R1 = 120 ohm
R3 = 1 ohm
D1 = ?
D2 = ?
P1 = 10K
Can you please help and tell me if LM337 will work? What are the values for diodes? Thanks
Vishwa, yes it will work, just make sure to adjust the pot to get a precise 4V at the output and not 4.2V.
D1, D2 = 1N5408
Sir,
Thanks for your prompt reply. Wish you and everyone following you, a prosperous and healthy new year.
Thanking you for your time,
You are welcome Vishwa, and Wish you too very Happy 2018
can i use any resistor in this circuit?please tell the values of r1,r2,r3,r4.
please specify the voltage output that you prefer to have, or the battery specification will also do.
hello Swag,
i found this Solar, Wind, 2-Input Hybrid Battery Charger Circuit https://homemade-circuits.com/2015/09/solar-wind-2-input-hybrid-battery.html which is very simple not getting zener diodes in my area.
moreover reading from the above the modern highly versatile chips like the LM 338 and LM 317 i can get all the parts for my personal project so i want to make a request from the above circuit.
I have •Maximum Power: 265w •Maximum Voltage: 31.4v •Maximum Power Current: 8.44a
•Open Circuit voltage: 38.6v •Short Circuit current: 9.03a solar panel with which i can modify and use
but the other side is the shunt regulator from the wind mill if you could please add a circuit of Lm 338 and LM 317 with out zener diodes so i could use as a dual charger.
thanks.
Hello Nito, a windmill should be ideally operated with a shunt regulator only, but if you are interested to have a LM338 circuit in its place you can easily do it by removing the entire opamp stage and replace it with a standard LM338 voltage regulator stage.
Hello sir.
First of all let me say thank you for your fast replays.
The FSD ammeter and R3 are not available at the market. Suggest somthg instead sir?
Best regard
Abubakar,
you can connect a suitably selected automobile bulb in place of the meter, initially this bulb will glow brightly, and when the battery is fully charged this bulb will shut down….but this will happen gradually…so you can consistently get the idea regarding the battery charge level through the bulb’s intensity level.
hello sir , can i use this circuit for 6v solar panel and 4v battery….???
yes you can use it for charging a 4V battery from a 6V panel, but preferably the panel voltage should be 3V higher than the battery voltage
THANK YOU VERY MUCH FOR YOUR CIRCUITS AND EXPLANATIONS. I AM SURE YOU HAVE A WHATSAPP GROUP.MY EMAIL ID IS easokgeorge@gmail.com CAN YOU ADD ME TO YOUR WHATSAPP GROUP. IF YOU CAN GIVE ME YOUR EMAIL ID I SEND YOU MY PHONE#. THANK YOU ONCE AGAIN FOR YOUR GREAT SITE AND SHARING YOUR KNOWLEDGE EASO K GEORGE.
.
correction: it should be above 5K, preferably 10K for enabling a full range control
100mah
yes the circuit can be used for charging the mentioned battery, but I am wondering how a 100 mAH battery could be used for operating an inverter
Pls sir can this circuit charger 12volt 100amh Inverter battery.?
100AH or 100mAH??
sir, please also send schematic for 12v 2.2Ah lead acid battery charger using solar pannel and power rating of pannel.thankU
Sir, please send me circuit diagram of the solar pannel charger
You can try the second circuit from the following link:
https://homemade-circuits.com/2013/12/usb-automatic-li-ion-battery-charger.html
replace the 1N4148 diodes with a single 6V zener diode, cathode will go to pin#2 and anode to the ground
thank U Sir
Sir, what will be the crt. of the charger
what is CRT??
its a circuit(ckt.) by mistake crt.
Hello Sir,
I have to charge 12v 2.2Ah Li-Ion battery using Solar pannel, will u suggest me what type of solar pannel should i use and what is the power, voltage, and current rating of pannel…
Hello Gaurav, you can use a 15V/1amp solar panel for your batt.
Sir Swagatam can this circuit charge a lithium ion battery? Im looking for a solar charger that can charge a lithium ion battery pack with overcharge protection .. thank you very much for your help sir..
Paul
Paul, yes it can charge a li-ion batt but you'll need to monitor the current level in the given ammeter and switch off the charging process when the meter needle drops to zero….initially it will show the charging current of the battery and gradually begin dropping…
for an automatic cut off you can opt for the second circuit from this article:
https://homemade-circuits.com/2011/12/how-to-make-simple-low-battery-voltage.html
Sir what's the meaning of the ground symbol between battery negative and R3.
should we connect it to pv negative by a separate connection?
it's the battery negative….don't bother about it, just make the circuit as given in the diagram…
hi sir,
im having a 12v 1 Ah battery(3*4v) and series pannel 6v+6v+3v = 15 v>
is it possible to charge the same with this circuit ??
Hi emil, yes you can use the above LM338 circuit for charging for battery…
sir could you please suggest any circuit for 1Hp single phase induction motor speed control, using PWM or variable frequency method.
Hi Shankar I think you can do it by using a standard fan regulator unit, by replacing its existing triac with a 40amp triac such as a BTA40A/600, you may refer to this article for more info:
https://homemade-circuits.com/2012/03/how-to-make-25-amp-1500-watts-heater.html
Hello Sir. I want to know if it is possible to charge a 12V 7A battery using a 9 V 3w solar cell using your circuit.
Thanks in advance.
Hi Garry, by what name have you sent the email? I could not find any
hi sir i sent an email,need your help for my project,very very tnx sir
sir do you know any current amplifier circuit that i can use because the output current from the circuit is very low, i recorded 200mA as the highest current that the circuit can supply so far which is not enought to fully charge the 40Ah battery. The panel is rated 100W and current peak is at 5.61A but it only supplies about 400mA input current to the LM338.
Nine, a current amplifier is out of question here….if your 100 watt panel is producing 400mA simply means it's faulty or something may be wrong with the connections….or if this happening after the LM338 IC stage would indicate a faulty or incorrectly wired LM338 IC….please check all these individually to confirm the results.
sir i'm still thinking if I should remove the relay in the circuit.. the setup now is that the relay serves as a switch for the sensor circuit, if the battery is in charging process the relay trips and the sensor is disconnected from the circuit so the charging current is divided to the battery amd relay.. if I do remove the relay the charging current will be divided to the battery and sensor circuit, however, the sensor circuit is composed of a voltage regulator, ATtiny mmicrocontroller, op amp, and a power mosfet for the LED.. I know the sensor circuit is quite large so it will really require a sufficient amount of current than the relay I think.. what would you do here sir?
Nine, the sensor circuit is not supposed to consume more than 5 to 7mA and the relay not more than 30mA….so it's your wish now whether to use the circuit or not as per the application needs.
thank you sir.. so I will connect it in parallel then and remove the relay now
also sir is it ok if I connected a dark sensor circuit parallel to the battery so the led lamp will automatically switch on at dusk? If yes, will it affect the charging process because the output current from the above circuit will be divided for the battery and sensor circuit?
yes it's possible, it won't affect the charging process since the current consumed by the system will be relatively smaller.
sir is that why the battery is dropping so quickly? also we also connected a regulator ic which is 7805 to bring down the voltage to 5V for our microcontroller, is 7805 also a factor why the battery is dropping? thank you sir
yes if the battery is not charged optimally, it will drop quickly, 7805 is not responsible for this at all.
hello again sir! i finally implemented the above circuit. I used a 100W solar panel to charge the 40Ah battery. First I used the battery to power the lamp and it dropped to 8V. I think the charging works fine because from 8V, the circuit was able to charge the battery to 13V. The problem now is that the battery is quickly draining, dropping to 8V after 2 hrs of supplying power to the 24W led lamp. The lamp still stays on but I think that should not happen to the battery dropping off too quickly. What would be the problem here?
Hello Nine, you must charge the battery up to 14.3V, for ensuring 90% charging….13v is not the optimal level for a 12V batt.
sir i'm a bit confused.. i followed all the calculations and it said I need at least a solar panel of 30W and a battery of 20Ah.. but you said before for a 24W lamp I will need a panel of greater than 50W and a battery of more than 40Ah.. sir please explain thank you
you might have calculated wrongly….a simple way is to divide 30 by 12, it gives 2,5A, how can a 2.5A charge a 40AH battery within 6 hours, it would take about 18 hours at that rate.
a 24 watt lamp will consume 24/12 = 2amps…so with a 40AH batt we get 40/2 = 20hours ideally but it would be just approx 12 hours practically
so you will have to charge a 40AH battery fully for sustaining a 24watt lamp for about 12hours
ok now I understand thank you sir.. anyways sir can I request for your insight on how to calculate the approriate battery and solar panel for our 12V 24W LED Lamp that should stay on for a whole night.. I just wanna have a concrete basis for picking the battery and panel..
you may refer to the following article for a detailed info:
https://homemade-circuits.com/2013/05/how-to-calculate-and-match-solar-panel.html
then it makes sense when the output voltage changes because the input voltage gets lower from the solar panel.. sir do you have any more circuit that can produce constant output regardless of the changes in the input?
….the output should be perfectly constant even if the input fluctuates widely but it should not be very close or lower than the intended load voltage
sir what should be the minimum input voltage from the panel so I can constantly produce 7V from the circuit using lm317? and what should be the minimum input voltage from the panel so I can achieve 14V from the circuit once I used the lm338?
It should just 1V higher than the required output, meaning for 7V output the input could be 8V…and for 14V output it needs to be 15V minimum
it's okay sir.. I just tried to put the panel under outdoor light even if it's cloudy.. now i'm getting up to 12V from the circuit.. I guess it makes a huge difference when you're testing it indoor.. now the problem is the output voltage keeps changing whenever I move the panel from different locations.. I adjusted the circuit to produce 7V but it keeps changing when I move the panel.. I thought this circuit will produce constant voltage once I adjusted the potentiometer regardless of the varying input voltage from the panel.. sir what is wrong here?
Yes the IC must produce a perfectly constant voltage regardless of a changing input.
Check and confirm the circuit first with a variable DC power supply and see the response.
sir i'm having problems with the circuit.. I tried. to construct this circuit in smaller scale so I bought a 12V 10W solar panel to charge s 6V 4.5ah battery. I used lm317 and I eliminated the transistor part because I want to see the output voltage first. But then the output voltage i'm getting is only up to 1volt. I checked the output voltage from the solar panel alone and its 7V. sir what am I doing wrong here? I haven't tried to put the panel under sunlight because it is cloudy here so i'm just testing it under indoor light.
Nine,
That's impossible unless you have done something wrong with the connections or have a faulty (duplicate) chip.
You may refer to this article for a better view of the concept:
https://homemade-circuits.com/2012/02/how-to-make-current-controlled-12-volt.html
sir what is the specs for the two diodes?
twice of the charge rate in amps
Hello sir. I would like to use the above circuit to charge a 3.7V 1500mAh mobile phone battery, with a 12V 5W panel. Can you please let me know the changes needed to be done to the circuit?
Hello LNB, the above circuit may not be appropriate for your application, you can try out the following instead:
https://homemade-circuits.com/2012/08/simplest-dc-cell-phone-charger-circuit.html
Make sure to replace the 9V zener with a 4.7V 1 watt zener and connect the 3.7 cell across the outputs indicated with a charger pin.
Hello, sir. I would like to thank you for your reply, and for the alternate suggestion. I just wanted to ask, couldn't I adjust the pot P1 to get 5V (4.2V battery's fully charged state voltage + 0.7V diode forward drop), and select R3 to get 10% of my battery's mAh?
Hello LNB, yes you may do it, please refer to the following article for the exact info
https://homemade-circuits.com/2014/12/12v-dc-solid-state-relay-ssr-100-amps.html
for Li-ion batts, 1/10th AH charge rate is not critical…you may apply even upto 1C rate that's equal to the Li-ions AH rating…
Hello sir. So, for a 1500mAh battery, i can use a 1.5A charging curent rating safely, as long as i remove the battery immediately after charging?? The only limitation is from the solar panel, isn't it?
i'm determined to use your circuit so what should be the input voltage and current for lm338? and is there anyway to adjust the output current?
input voltage is 32 max, current doesn't matter it can be anything as long as volatge is within 32V.
the max output current can be set anywhere from 0 to 5amps by selecting different values for R3 as per the calculations
how bout a 60- 80 watt panel?
Yes, you can try it out, might just work.
what if I used a battery of 45Ah or 50Ah?
yes will do but a 50 ah battery will need a higher wattage solar panel for fast charging, it will charge very slowly with the existing 50watt panel
what do you suggest sir that I do to make it longer?
There's no way to increase the back up time, unless another battery in parallel is used…. but that will require upgrading the panel to 100 watts.
for the current rating of the solar panel (12V 50W), what do you suggest I use sir? a 12V 40Ah lead acid battery or a deep cycle battery?
note: the battery should be able to supply enough power to the LED lamp for the whole night (12 hours at most). thank you sir
deep cycle batteries are also lead acid batteries, so you can use a 40AH lead acid battery for the said purpose.
The mentioned 24W lamp can be operated for not more than 6/7 hours at stretch with a fully charged 40AH batt.
sir this is the current setup of the project..
12V 50W solar panel to charge a 12V 40Ah lead acid battery, the load will be 12V 24W LED lamp
what are your thoughts about these adjustments? and can the circuit above can charge a deep cycle battery? thank you so much sir for answering my questions
yes a 12V 50 watt panel can be used for charging a 12V 40AH deep cycle battery, but will require around 10 hours to get fully charged.
a 12V panel during peak should be producing 15 to 16V, so according to me you can connect it directly with the battery through a 6A4 diode…the above circuit may not be required.
sir if that's the case, can I still use the above circuit? by the way it's 12V 55ah battery
for a 12V battery a 50 watt panel can be used, but the panel peak voltage should not be above 15/16V for an optimal response,
yes the above circuit will just fit in.
sorry sir it's a 12V battery
ok sir i'll research more on that.. anyways can I use a 24V 50W panel to charge a 55Ah 22V battery, by the way the battery will supply a 12V 45W LED Lamp.. what's your opinion about this sir?
Nine, you will require a minimum 125 watt panel for charging the specified battery….50 watt will not do it satisfactorily.
goodday sir what kind of ic will i use to charge 12v 9ah lead acid battery from solar cell of 12 volt 10 watt
GEA, 12V solar panel will not charge a 12V battery, It should be around 16V solar panel, with 1 amp current
correct me if I'm wrong sir, but you're assuming that the battery is rated @10 hr. I will be using a battery that will be rated @20 hr, so i can use a maximum of 100Ah because 100/20= 5A, which is the maximum output current of LM338..
I don't know if a lead acid battery can be charged at AH/20 or C/20 rate, so I can't say much about this calculation…C/10 is considered as the minimum optimal range for charging lead acid batts.
sir what is the maximum Ah that this circuit can handle? and can you teach me how to add an overcharge protection circuit to this one because i need the circuit to automatically stop the charging when battery is full.. thank you
Nine, the LM338 IC used in the circuit can handle up to a 50 AH battery for charging.
sir can you explain the role of each component in the circuit? i wanna understand how each of them function.. and how did you come up with the computation R3=0.7/chg. current? thank you so much sir!
The upper resistors are as per the IC datasheet…the BC547 is responsible for grounding ADJ pin of the IC and disabling it when an over current is sensed, and this happens when the potential across R3 exceeds 0.7V which is the switch ON (saturation) voltage of the transistor
Hi sir
I wanna ask if i can use this circuit to charge a 12v 40W lead acid battery ti powerup an LED lamp during the night. I'm planning to use this for a streetlight.
Hi Nine, did you mean a 40 AH battery? Yes you can use the above circuit for charging a 40AH batt, make sure to put the IC LM338 on an adequately large heatsink
Hi sir,
I realised the circuit of this article but I can manage only the voltage at the output with the potentiometer, not the current. What could it be wrong? I didn't put the R4 and I switched the multimeter as ammeter and connected it in series the output of circuit with the battery.
Hi Daniele
R4 is not required anyway, so the current limit will still work for you depending upon the selection of R3
…the pot is only for varying the voltage not current, current can be managed by altering R3 as explained in the article.
Thanks, I really appreciate your help, the circuit works, finally! 😉 I have just one more question: there is any ways to evaluate the charging current? I have two batteries in parallel, one is 10Ah e another one 4.5Ah. The solar panel produce 1,7A and the R3 is 0.47ohm. I guess I made the correct calculation but I would check the real current that pass on the circuit. Any suggestions? Thanks in advance for any answer 🙂
Thanks Daniele,
Usually it's AH/10 for lead acid batteries and AH/1 for Li-ion batts, but if you have two batts in parallel with different AH rating in that in case you may have incorporate separate current limiting circuits for each batts.
You may have to make two of the above circuits, and calculate R3 separately in order to feed the respective batts…the ground will be common for both the circuits.
actually i want to make charging my 24 volt 1.5 Ah battery to supply 24 volt, 600 mA STEPPER MOTOR…..
is this possible from 12 volt 250 mA solar panel using 12-24 volt boost converter???
No it won't, it's the same situation as previously explained…
ok… so according to you i should connect two 6 volt, 250 ma panels in series… then i will get 12volt 250ma…. am i true sir??
yes that will do but the voltage will need to be at least 14V to initiate the charging….
thank you for your reply…
but sir if i will place a boost converter in between solar panel and battery…..is it true??
….for that your solar panel supply should be rated to generate at least 1amp output, 250mA will not do.
have a good day sir!!!
plz help me about my question that, is it possible to charge 12 volt 1.5A battery from 6 volt 250 mA solar panel?????
good day Tejas,
No that's not possible, the voltage should be minimum 14 V
Sir, i have 70Ah 12volt battary and i'm about to buy 100Ah solar panel to charge it. there need to be solar charging system(circuit)? could i connect battary directlly from solar panel for charging? it will harmfull for battary?
Dev, solar panel current is not rated with AH, its rated with amps….a controller can be avoided by selecting a correctly rated solar panel for the battery.
for a 12V 70ah battery use a 18 V, 10amp solar panel….18v is the peak rating of the panel and 10amp is the short circuit current of the panel
thanks
hii sir,
Is there any single chip IC for dust sensor and sound sensor??? If no please suggest me a simple circuit… thanks
hi Vipu, sound can be sensed by a mic, I am not so sure about dust detection.
Thanks sir i have assembled all the components except this resistor…. taking your suggestion i will progress the circuit and tell you about the output ….
Sir do you have a of DC 12v to 18v or 24v DC converter circuit i am not not getting this in your site…can you please help me…once again thank u …
Bhanu, you can try the following converter circuit:
https://homemade-circuits.com/2012/09/led-emergency-light-circuit-using-boost.html
Sir me bhanu can u plese tell me how to calculate charging current easily….
You have given a formula i.e 0.6/Charging current
Can i use 0.6/ battery Ah or i will take 1/10th of battery Ah
0.6 should divided by 1/10th of battery AH.
sir, what is the charging current of 12v 7Ah battery? what is the diode use in here?and what is the watt of resistor to be use?..thanks
Erns, R4 is not needed, you can remove it.
the ideal charging current of a 12V 7ah battery is around 1amp.
the diode is for preventing accidental polarity reverse conditions at the input.
sir,
I want to design a solar battery charger,all components should be SMD type and my aim is to reduce PCB size as much as possible…pls help me…
Vipu, what specifications do you want for the solar charger circuit?
still we are not finalised,but mostly it wiil be 5V/6V battery charger….but i need a circuit for my reference,can u send me?….pleaseee
should it be automatic, or manual?
should be automatic
you can try the second circuit from the following link, except LM317 all other parts could be SMD
https://homemade-circuits.com/2012/07/make-6v-4ah-automatic-battery-charger.html
thanks for your help..
hiii…
I have 1 more doubt,how to connect a temperature sensor TMP100 with a CC2541 IC.Should i use I2C pin or any other digital I/O pin???? thanks
I'll have to do some research on it before suggesting…..
sir,
I have to drive robot which require 12 v,1.5 amp to operate .So,please help me to decide which solar panel and rechargeable battery i have to use.
battery can be a 12V 7.5ah and the solar panel = 14v, 1amp
sir,
i want to charge a 12 volt 5 amp battery using this circiut in your blog..what would be the specification of the solar pannel..plz help.
You can use a 18V/1amp solar panel for it.
What is the modifications in the circuit if i want to charge 24 v battery with 12 v of solar panel input.
that's not possible with this circuit.
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