The post explains a simple solar battery charger circuit using the IC LM338 which can be built and installed by even a layman for achieving the intended results.
Solar Panel Installation
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.
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.
Andre Delgado says
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.
Swag says
Andre, you can use the first design from the following article:
https://www.homemade-circuits.com/solar-charger-circuit-using-transistors/
Andre Delgado says
Does this cut off the charging process when the battery is full? It is not Simple afterall.
Swag says
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
Pacifico Sariego says
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
Swag says
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….
Pyke Sariego says
Thank you very much sir. I appreciate very much you prompt and informative response. Keep up the good work. I salute you
Pyke
Swag says
you are most welcome Pyke!
Sharath says
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
Swag says
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.
Vishwa Mukh Bharadwaj says
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.
Swag says
That looks great Vishwa! Thanks for posting
Vishwa mukh says
Sir,
Thanks for your valuable and kind appreciation.
Vishwa mukh says
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,
Swag says
You are welcome Vishwa, you can use my circuit diagram in your youtube video with a backlink to my site, let me know when you have posted it.
Vishwa Mukh Bharadwaj says
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.
.
Swag says
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
Vishwa mukh says
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.
Swag says
OK, then everything is fine.
Bhavani says
How much cost to make the circuit
Vishwa mukh says
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
Swag says
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
Vishwa mukh says
Sir,
Thanks for your prompt reply. Wish you and everyone following you, a prosperous and healthy new year.
Thanking you for your time,
Swag says
You are welcome Vishwa, and Wish you too very Happy 2018
ishwarya says
can i use any resistor in this circuit?please tell the values of r1,r2,r3,r4.
Swag says
please specify the voltage output that you prefer to have, or the battery specification will also do.
Nitonito says
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.
Swag says
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.
Abubakar says
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
Swag says
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.
adblogs says
hello sir , can i use this circuit for 6v solar panel and 4v battery….???
Swagatam says
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
EASO GEORGE says
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.
.
Farrar Mike says
100mah
Swagatam says
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
Farrar Mike says
Pls sir can this circuit charger 12volt 100amh Inverter battery.?
Swagatam says
100AH or 100mAH??
gaurav yadav says
sir, please also send schematic for 12v 2.2Ah lead acid battery charger using solar pannel and power rating of pannel.thankU
gaurav yadav says
Sir, please send me circuit diagram of the solar pannel charger
Swagatam says
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
gaurav yadav says
thank U Sir
gaurav yadav says
Sir, what will be the crt. of the charger
Swagatam says
what is CRT??
gaurav yadav says
its a circuit(ckt.) by mistake crt.
gaurav yadav says
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…
Swagatam says
Hello Gaurav, you can use a 15V/1amp solar panel for your batt.
Paul says
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
Swagatam says
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
Yupoyu says
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?
Swagatam says
it's the battery negative….don't bother about it, just make the circuit as given in the diagram…
emilsonusam says
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 ??
Swagatam says
Hi emil, yes you can use the above LM338 circuit for charging for battery…
Shankar ks says
sir could you please suggest any circuit for 1Hp single phase induction motor speed control, using PWM or variable frequency method.
Swagatam says
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
computis says
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.
Swagatam says
Hi Garry, by what name have you sent the email? I could not find any
Garry Gutierrez says
hi sir i sent an email,need your help for my project,very very tnx sir
Nine says
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.
Swagatam says
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.
Nine says
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?
Swagatam says
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.
Nine says
thank you sir.. so I will connect it in parallel then and remove the relay now
Nine says
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?
Swagatam says
yes it's possible, it won't affect the charging process since the current consumed by the system will be relatively smaller.
Nine says
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
Swagatam says
yes if the battery is not charged optimally, it will drop quickly, 7805 is not responsible for this at all.
Nine says
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?
Swagatam says
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.
Nine says
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
Swagatam says
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
Nine says
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..
Swagatam says
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
Nine says
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?
Swagatam says
….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
Nine says
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?
Swagatam says
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
Nine says
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?
Swagatam says
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.
Nine says
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.
Swagatam says
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
Nine says
sir what is the specs for the two diodes?
Swagatam says
twice of the charge rate in amps
LNB says
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?
Swagatam says
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.
LNB says
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?
Swagatam says
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
Swagatam says
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…
LNB says
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?
Nine says
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?
Swagatam says
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
Nine says
how bout a 60- 80 watt panel?
Swagatam says
Yes, you can try it out, might just work.
Nine says
what if I used a battery of 45Ah or 50Ah?
Swagatam says
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
Nine says
what do you suggest sir that I do to make it longer?
Swagatam says
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.
Nine says
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
Swagatam says
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.
Nine says
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
Swagatam says
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.
Nine says
sir if that's the case, can I still use the above circuit? by the way it's 12V 55ah battery
Swagatam says
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.
Nine says
sorry sir it's a 12V battery
Nine says
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?
Swagatam says
Nine, you will require a minimum 125 watt panel for charging the specified battery….50 watt will not do it satisfactorily.
Nine says
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..
Swagatam says
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.
Nine says
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
Swagatam says
Nine, the LM338 IC used in the circuit can handle up to a 50 AH battery for charging.
Nine says
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!
Swagatam says
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
Nine says
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.
Swagatam says
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
Daniele says
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.
Swagatam says
Hi Daniele
R4 is not required anyway, so the current limit will still work for you depending upon the selection of R3
Swagatam says
…the pot is only for varying the voltage not current, current can be managed by altering R3 as explained in the article.
Daniele says
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 🙂
Swagatam says
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.
TEJAS PARMAR says
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???
Swagatam says
No it won't, it's the same situation as previously explained…
TEJAS PARMAR says
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??
Swagatam says
yes that will do but the voltage will need to be at least 14V to initiate the charging….
TEJAS PARMAR says
thank you for your reply…
but sir if i will place a boost converter in between solar panel and battery…..is it true??
Swagatam says
….for that your solar panel supply should be rated to generate at least 1amp output, 250mA will not do.
TEJAS PARMAR says
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?????
Swagatam says
good day Tejas,
No that's not possible, the voltage should be minimum 14 V
Dev Aarya says
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?
Swagatam says
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
shahab ali says
thanks
vipu says
hii sir,
Is there any single chip IC for dust sensor and sound sensor??? If no please suggest me a simple circuit… thanks
Swagatam says
hi Vipu, sound can be sensed by a mic, I am not so sure about dust detection.
bhanu prasad Mishra says
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 …
Swagatam says
Bhanu, you can try the following converter circuit:
https://homemade-circuits.com/2012/09/led-emergency-light-circuit-using-boost.html
bhanu prasad Mishra says
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
Swagatam says
0.6 should divided by 1/10th of battery AH.
Erns Balana says
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
Swagatam says
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.
vipu says
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…
Swagatam says
Vipu, what specifications do you want for the solar charger circuit?
vipu says
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
Swagatam says
should it be automatic, or manual?
vipu says
should be automatic
Swagatam says
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
vipu says
thanks for your help..
vipu says
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
Swagatam says
I'll have to do some research on it before suggesting…..
the devils says
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.
Swagatam says
battery can be a 12V 7.5ah and the solar panel = 14v, 1amp
Abhishek Dhua says
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.
Swagatam says
You can use a 18V/1amp solar panel for it.
Ashwini Chavan says
What is the modifications in the circuit if i want to charge 24 v battery with 12 v of solar panel input.
Swagatam says
that's not possible with this circuit.
Mrinal Kawale says
is this circuit can be use to charge 4.7v mobile battery by using 12v solar plate? and how long will it take to charge my battery?
Swagatam says
yes it can be used, calculate R3 = 0.7/battery AH
it will take about 1 and 1/2 hours to charge it fully.
Anonymous says
sir,how can we increase the current at the output if the output voltage is 6.52 but in my case current is too low?
Swagatam says
current cannot be increased, it will be always equal or less than the input source.
jaguar says
hi sir,
how can i charge a 12v 130AH battery with solar plates can u show the circuit diagram
Swagatam says
hi jaguar,
you will need a 200 watts 24V solar panel for this….do you have it?
Anonymous says
i want ask if i can use LM7812 instead of LM338
Swagatam says
no….
Rizmy Mohomed says
Sir,
Then the maximum output will not be sufficient to charge a battery ryt… Then how to boost the voltage here sir?,
Swagatam says
For boosting the voltage upto the battery level you will require the following circuit, but the current from the turbine source should be strong otherwise the boosting will not take place.
https://homemade-circuits.com/2013/03/how-to-convert-12v-dc-to-220v-ac-using.html
Rizmy Mohomed says
hello sir,
can i use this cct for a small scale wind turbine which gives an output ranges from 5V to 15V?… i need to charge a battery using that. so please help me on this sir.
Swagatam says
hello Rizmy,
you may use it to get a fixed maximum voltage output as per the setting of the preset, but you won't get any voltage boost from this circuit.
Shankar ks says
sir i did this circuit and using for 100watts panel the voltage is regulated and output is ok but the LM338,TIP36 and all other components including resistors were getting too hot with in a minute. why? will this affect circuit components.
Swagatam says
which circuit are you referring to? show me the circuit diagram I'll check it.
Shankar ks says
https://homemade-circuits.com/2012/02/how-to-make-solar-inverter-circuit.html
this charge regulator circuit.
Swagatam says
what is the voltage from the solar panel, LM338 cannot handle more than 32V
Shankar ks says
21 volt from solar panel.
Swagatam says
what is the value of R3, the transistor or the IC will become hot only in case the current exceeds their limits.
R3 must be dimensioned properly, make it 0.05 ohms/ 10 watts
use two 0.1 ohms 5 watt in parallel
R4 can be removed, short it with a wire link.
ayyappa reddy says
hello sir
could u please mail me the complete operation of solar battery charging circuit
mail id: ayyappareddy239@gmail.com
Swagatam says
Hello ayyappa,
I have explained everything in the article, if you have specific questions you can ask them here.
sasikala srinivasan says
THANK YOU SO MUCH SIR .. I got the output and as you have already said that using LM317 will limit the output to 1 Amp. How can I utilize this 1 Amp current Sir?
I'm so happy the I have completed the circuit Sir. Thank you so much and all the conversations helped me gather information. Thank you users for giving your views… Thank you once again Sir.
Swagatam says
You are welcome sasikala!
you may use it for any circuit application like for driving LEDs, for charging a battery etc.
to be precise the IC will limit anything above 1.5amps, but you can set R3 for any desired current of your choice.
Rashid Ansari says
Hello Sir,
I am a bit confusing in selecting the right solar cell.
I have a small 12v 18AH battery. Please tell me the specs of solar panels, like volts and watts.
Also please give me the formula to calculate it with different ratings of batteries.
Thank you so much.
Rashid
Swagatam says
Hello Rashid,
you may use any type of panel which is able to provide more than 14 V for 6 hours at 1/5th current of the battery AH.
Rashid Ansari says
Hello Sir,
Really appreciate your help.
Thank you.
Rashid
NIYAM PATEL says
HERE USING SOME DIODE AND AND RESISTER WHICH I CAN'T DEFINE THE VALUE OF R1,R2 AND DIODE…….SO PLEASE TELL ME SIR….THANK YOU.
Swagatam says
The diode current value will depend on the specified charging current at the output, same for the values of the resistors, calculate it using the given formula.
sasikala srinivasan says
Good evening Sir
I'm trying out your circuit which was previously posted and that circuit resembled the same like the above but 'dint have a diode' at the pin out of LM338 to the battery negative? so what diode should I place here?
Then Sir I'm using LM317 , so please tell how to preset adjust to 7v at output? Please help me as I'm doing my undergraduate project in 'construction of solar panel regulator'.
Thank You Sir
Swagatam says
Hello Sasikala,
The diode prevents the battery from getting discharged in the absence of voltage from the IC or from the solar panel, so it is a must.
LM317 and LM338 are similar with their operations, for 317 also you would have to adjust the given preset P1 to get the required voltage at the output.
Syed Imroze says
hi sir i want to clear one thing i am looking for this type of batter charging ckt but i need auto cut-off ckt for this can u help me. are any reference
i want develop my self but i dont have any guidance i hope u can help me
Swagatam says
Hi Syed,
Please check out the last circuit in the following article:
https://homemade-circuits.com/2012/07/making-simple-smart-automatic-battery.html
Anonymous says
thank you sir. more power.. god bless..
Anonymous says
good day sir! i dnt understand R3=2R3. can you please explain sir. please. i have no idea. hope you understand. im carrem from the philippines.
Swagatam says
Good day Carrem, actually R4 is not required according to me. R3 is sufficient, however in the datasheet both these resistors are included so I have provided exactly what's given in the datasheet of the IC338.
Anonymous says
can i know the wattages of the resistors used plz.
Swagatam says
All are 1/4 watt, except R3/R4 which may be 1 watt or more
Gyanendra Bhattarai says
Hello Sir,
In most of the panels, the Open circuit voltage, Voltage at maximum power and voltage at rated load are given. But I want to know whether the panel voltage drops to 10 volts, 9 volts or below which, I think can not be used to charge a 12V battery.
I want to know whether a circuit can be designed to upscale the voltage in that situation to charge the battery however with small current. Or, is the circuit you have given here capable to do that?
Incorporating the feature in the charger circuit would be best to use the maximum possible energy produced from the panel.
Regards
Gyanendra
Nepal.
Swagatam says
Hello Gyanendra,
As far as I know, as the voltage drops, current also drops in solar panels with decreasing sunlight…..though there are ways to step up or boost the voltage using boost converter circuits, the current will decrease proportionately and will be adequate may be just for trickle charging purpose of the battery.
Regards.
Anonymous says
LM338 as in LM338K or LM338T?
Swagatam says
yes that's right, all will work here…..
Anonymous says
A series diode at output is needed to avoid battery discharging or LM damage when no input voltage at regulator..the only thing that was missed here.
Swagatam says
Right! Thanks.
Access News Service says
Question on component P1 – Looks Like a 2K Pot is this a voltage adjustment? Can you say more on P1 Watts etc…
Swagatam says
Yes P1 can be either a 2K pot or preset, any normal type will do, high wattage is not required.
Swagatam says
correction: it should be above 5K, preferably 10K for enabling a full range control
Rashid Ansari says
O.K Sir,
It means according to W=V*I, it should be 150W.
Thank you.
Best Regards.
Swagatam says
Yes you are approximately correct….
Regards.
Swagatam says
The open circuit voltage of the panel should be around 30v and the short circuit current must be rated at 5 amps.
Rashid Ansari says
Sir,
Also please explain how to get the value of R3 easily.
Thank you again.
Swagatam says
The charging Current should be 1/10th of the battery AH, now you can calculate yourself.
Rashid Ansari says
Hello Sir,
Solar panel should be of how many watts and volts ?
Please reply.
Thank you.
Anonymous says
i want a battery which provides me 12volts for my oder circuit wat changes do i do?
Anonymous says
your all full of your self …
Rajagilse says
Sir, as the battery voltage does not reach above 13.7 ( as you replied), then no chance of harmfull reaction. Isn't it? Ok, if it starts in 13.7 itself, what happens if i decrease the charging voltage as , say 13.5 volt. And even charging current also i.e. Say 200 mili amps. I know the charging is very slow. My aim is to find out whether battery become over chargied or not , in certain charging voltage and current condition, even in absence of auto cut off. Give your opinion
Swagatam says
If you reduce the voltage, the battery will attain only 75% charge but yes the battery will not get over charged.
The right process is to charge the battery with high current up to 14.4 volts then switch the charging to very low current and continue for another few hours and then shut off the power, in this way the battery will reach at least 90% of its capacity.
Rajagilse says
SIR, What happens if i charge 12 volt 3 ah lead acid battery by giving exact 13.7 volt dc through LM 317 continuously i.e. unattended for more than 2 days? Charging current is 0.3 amps
1. Whether the 12 volt battery charges or not ?
2. Whether the battery over charges i.e. Whether the battery voltage raises more than 13.7 volt ?
3. Whether Charging stops after the battery will attain 13.7 volt ?
Swagatam says
1) Battery will get charged within 14 hours.
2)Battery will slowly get overcharged and its life will deteriorate. Battery voltage will not reach above 13.7V but harmful chemical reactions will start taking place inside the battery.
3) Charging process will not stop and the battery plates will start getting damaged slowly.
Rajagilse says
Unless battery voltage will not reach above 13.7 volt, how the harm full chemical reaction starts to deteriorate the cell? Because normally 13.8 or above up to 14 volt is taken as full charge for 12 volt battery , under charging
Swagatam says
If the current is not reduced after 14 hours of charging, harmful chemical reactions will start taking place at 13.8V, which is the fully charged condition of a 12V battry. 300mA rate means 1/10th of 3AH which can be dangerous after 14 or 16 hours of charging.
You can read this article for further info:
www.operatingtech.com/lib/pdf/A%20Guide%20to%20battery%20Charging.pdf
Mho says
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?
Swag says
that is correct!
Rajagilse says
When the ammeter reads zero at the full charge of battery, then how it further charges to get over charged ? As the ampmeter reads zero means no current i.e. No charging am i right sir?
Swagatam says
The battery is not consuming any current because it's trying to obstruct the charging process, but the voltage from the charger is forcing the battery to get charged and therefore slowly after many hours the battery voltage will keep rising, crossing the danger mark and dangerous chemical reactions will start taking place inside the battery, reducing its life and efficiency.
Rajagilse says
Thank you sir, thanks for explaination
Rajagilse says
Sir, if battery is not disconnected manually after full charge , whether battery becomes over charged or charging stops after full charge?
Sir, as R3 =0.7/ charging current , how can i get some non standard value of resistors? Could i use variable resistors?
Swagatam says
Battery will get overcharged, you will have to remove it manually when the meter reads zero volts.
You can adjust the value by adding a few resistors together in parallel or in series to reach the approximate value.
Anonymous says
What happens when the battery is full? Thank you in advance for your help.
Avisek Chakraborty says
waht modification in the circuit is needed if i use lm317
Anonymous says
Swagstram,
Is the emmitter "floating", or is the solar panel negative not commoned with the battery negative. If they are commoned then the transistor will not do it's job.
Regards
Richard
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