How to Make a 12V Lead Acid Battery Charger Circuit

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Posts: 1
Joined: Mon Apr 08, 2019 2:00 am

How to Make a 12V Lead Acid Battery Charger Circuit

Post by zhengxuqi » Mon Apr 08, 2019 2:08 am

Step 1: List of Components:

Here is the list of components with valid purchasing links. so you can buy easily.

R1,R3 = 1K

R4,R5 = 1.5K

R6 = 10K

R7 = 1.2K

R2 = 1R5W

PR1 = 50K

Q1 = D882

D1 = 1N4732A

D2,D3,D4 = 1N4007

Relay = 12V

U1 = LM7815

5MM LED = Red,Green,Blue,Yellow

Alligator Clips = 2

Jumper = 1

Step 2: How to Make?

To make this project, you also need a circuit diagram, which you can download from here for free!

After understanding Circuit diagram, of course, you will need a PCB. But don't worry, you will not need to design it. Here is a solution!

Just go here:, then upload free PCB Gerber files from the link given below. They are really professional PCB manufacturer and they have the cheapest prices that I have ever found

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Step 3:

After collecting all material, Simply solder all components to your new printed circuit board according to the circuit is easy! then connect some extra piece of wires to connect input with a power supply, and output with a 12V Lead Acid battery. After soldering all components and wires, you will need a little bit calibration.

Step 4: ​Calibration of Circuit:

To calibrate the circuit, set your DC regulated power supply at 14.5V and connect +ve wire to the CB+ of circuit and -ve wire of power supply with CB- of the circuit. now turn the potentiometer slowly until blue color LED lights up. After that, disconnect power supply, and connect the "Jumper" on circuit board. Now your circuit is ready to use. connect a battery at the output and set your DC power supply at 16VDC to 18VDC and connect it at the input of circuit.

Step 5: ​Working:
Basically, this circuit is very simple, based on a single transistor, a zener diode, a 12V relay and some resistor and diode networks. we set a tripping voltage level by using a potentiometer and a resistor network. when the charging voltage reaches that certain value(i.e 14.5V), the zener diode conducts and provide a signal to the base of transistor and makes the output of transistor high which causes the relay to activate and cut off the charging input for the battery.

I designed this circuit to charge your battery @ 70% to 75% only due to some safety reasons. If you want to make it for 100% charging, then remove the LM7815 and connect directly 18VDC supply and set tripping point at 15.8 ~ 16V. and always use 5 to 6 times lower charging current from the maximum value of battery current. i.e 1.2A for a 7AH battery.

*This circuit has not any current limiting feature.(except 1R5W Resistor)

**This circuit is not 100% Perfect, but it is still very useful for hobby/DIY projects.

Posts: 1
Joined: Tue May 07, 2019 12:10 am

Re: How to Make a 12V Lead Acid Battery Charger Circuit

Post by a_hakeem » Tue May 07, 2019 12:23 am

Thank You for the project but i don't see the circuit

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