The post details a simple automatic High Voltage Battery Charger Circuit which can be used for an automatic charging control of any preferred high voltage battery bank such as a 360V battery bank. The idea was requested by "resonance".
Circuit Objectives and Requirements
- I found all your circuit and projects interesting but please I need a special assistance.
- I want to build a Low and high battery full cutoff that can handle about 360VDC (30 Batteries in series) such that when battery is full at 405VDC charging Voltage will cutoff and when battery drop to like 325VDC it also cutoff battery low.
- Please, do share this experience with me.
Circuit Diagram
The Design
The figure above shows a straightforward configuration for achieving the proposed automatic high voltage battery charger circuit in the order of 360V.
The idea is based on the standard opamp based comparator principle, which is also implemented in many of the earlier 741 based battery charger circuits.
The circuit functionality can be understood as explained below:
The 360V is achieved by adding 30 nos of 12V batteries in series, which constitutes 430V level as the full charge threshold, and 330V as the full discharge level threshold.
The battery bank voltage needs to be controlled within these limits for ensuring a safe charging environment for the batteries.
The opamp circuit is configured for implementing the above mentioned high voltage charging control as indicated in the diagram.
The 360 V is stepped down to a suitable proportional level for the opamp sensing input at its inverting pin#2 applied via a 10 k preset. This is done through a potential divider network using a 220 k and a 15 k resistor.
The non-inverting pinout of the opamp is clamped at 4.7 V through a zener diode for providing a reference to its complementing pin#3 sensing input.
The operating supply voltage for the opamp pin#7 is extracted from one of the batteries associated with the negative line of the system.
Preset Adjustment
The preset is adjusted such that the opamp output pin#6 just becomes high and triggers the transistor when the battery voltage reaches at around 430V.
The above action forces the relay to operate and cuts off the supply charging voltage to the battery bank.
As soon as this happens, the battery voltage tends to go down a bit which normally prompts the opamp to trigger back the relay ON, however the presence of the feed back resistor connected across pin#6 and pin#3 holds the opamp situation, and prevents this from happening.
This is also called the hysteresis resistor which temporarily latches the opamp to a certain voltage range depending on the value of this resistor (Rx).
Here it must be selected such that the opamp stays latched until the voltage of the battery bank drops to about 330V, after which the opamp could be expected to restore the relay back in its N/C position initiating the charging process for the batteries.
Hi swagatam sir, I need variable auto cut off circuit for charging different lithium & lead acid batteries. ex:- 12v – 100v & 20-100amp batteries. . can I use this circuit. Please clear that is this ok for that or any changes I have to do.
-This circuit works on which min. & max. voltages & charging amp support? ?
-What will be the relay configuration for max 20 amp charging current?
-Can I use variable resistor in Rx place?
-Any Zener diode modification?
Hi Subroto,
The above circuit will need many modifications to charge batteries from 12V to 100V.
Instead I would recommend trying the last circuit from the following article:
https://www.homemade-circuits.com/make-this-48v-automatic-battery-charger/
Hello sir, a/c ur recommendation 48v last circuit if I use, what voltage range of lithium batteries will work on that circuit. Means for 48v, 60v ,72v , atleast I need.
Or could u please make a auto cut off circuit diagram for 48v ,60v ,72v lithium batt.( as li-ion & Lpf has diff.cut off volt ) with voltage set preset . ampere preset not required bcz the amp. Can adjusted from input boost convertor. The circuit will support atleast 15amp of charging current ..
Hello Subroto,
You can charge all those batteries using the previous linked circuit but the setting of the trimpot will be different for each battery. As it is difficult to adjust the trimpot again and again for the different batteries, so I would recommend making separate circuits for the 3 batteries. Also make sure to replace the BC546 with TIP31C so that upto 72 V battery can be charged..
The circuit has an auto cut off feature included in it.
The last circuit has a current control which you can set as per the battery specifications.
Circuit will support 15 amps.
Thank u sir, I will try this.
Sir plz clear which one is preset & which one resistor, not mentioned . I am using ur 48v circuit having tip36 without current control . from 48v battery side there is 22k &10k in series , one more 22k parallel to 22k . another wire of 56v input ,10k between base & collector point of tip36 & bc546.
I thank 10k preset is on 48v side which is connected to 2no. Pin of ic 741.
22k preset??
Red led is on 6no.pin -right..
Green led ???
Subroto, Yes, the 10K connected with pin#2 of the 741 IC is the preset.
One 22K K is connected in series with the above 10K preset.
Another 22K preset is connected with the pin#3 zener diode.
RED LED connected at pin#6 or the output of the IC.
There’s no room for a Green LED.
https://www.homemade-circuits.com/wp-content/uploads/2022/09/simpel-48-V-batery-charger-circuit.jpg
how to control the current in this schematic ? and if its NO position , isn’t the 430v charging input supply is directly short circuiting with the battery bank ?
You are right, the 430 V must be current controlled. You can add a series non-polar capacitor with the AC source of the 430V for controlling current. a 1uF capacitor will restrict the current to around 50 mA. Using this benchmark you can calculate the value of the capacitor depending on how much current limiting your battery requires.