12v Battery Charger Circuit with Overcharge Protection
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This 12-battery charger circuit provides an Automatic cut-off facility when the battery gets fully charged. Before using this circuit, you need to adjust the Cut voltage range for the auto cut. This adjustment is done by moving the 10k preset, and for testing the output voltage auto cut range, a multimeter is connected to the output terminals that go to the battery. This voltage range can be set by using any 13v or 14v DC supply that connects the terminals that go to the battery. And moved the preset till the green led ON. Once the auto-cut voltage is set, the circuit is ready to use.
One terminal of Input AC power to the Transformer is connected through a 12 V Relay. When the Battery needs charge then the Red LED glow. When the Charge level goes to about 12v or 13v, then the Red LED will turn off, and the Green LED will glow. And the Input Power to the Transformer of the charger is also disconnected by the Relay.
12v battery charger with auto cut-off circuit diagram
One 555 timer ic is used for detecting the voltage level, and a Relay is used to disconnect the AC input. 7808 voltage regulator is used for constant supply to the operation of the circuit to cut at a required fixed voltage.
This 12v battery charger automatically cuts the circuit after a full charge and provides 6 Ampere high current, and this can use for a big-size Lead-acid Battery up to 100 AH. If you want more higher current, then replace the transformer with 10A and use a 10A10 Diode. You can use a ready-made 12v 10 A Bridge Rectifier, which is available in the market.
Schematic diagram
circuit 1
Components
Diode
6A8 or 6A10- 4 pc
1N4007 – 1
7808 ic – 1 pc
555 timer ic – 1 pc
Capacitor
1000uf 50v – 1pc
1000uf 25v – 1pc
100nf (104) – 1 pc
Resistor
10K – 1
5k – 1
470 Ω – 2
Relay 12v 6 A – 1
Preset 10k – 1 pc
LED 1 pc – Green
LED 1 pc- RED
Transistor BC547 -1 pc
10 amp battery charger circuit diagram
Circuit 2
Connect positive output wire on NC through Common pin of Relay
Parts (circuit 2)
Transformer 0-14V (10A)-1
Diodes
MIC10A-4
1N4007-1
Capacitor 1000uf 50v – 1
Resistors
2.2K-1, 150R-1
Preset RV1-10K-1
Transistor BC547B-1
Relay 12v (10A)- 1
LED- 2 ( Green -1, Red-1)
Circuit 3
This circuit has a maximum current capacity of 1 A only.
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230v ac to 12v dc and 5v dc Regulated Power Converter
What is mosfet, ? thet i know no.
I built a 2kva inverter, and now I need a circuit that can charge a 100 amps battery
hello, sir I have one question?
how can we make auto on battery charger when the battery is low
Hi sir,
I am designing a lead acid battery charger with autocut off feature.
I build a circuit as mentioned in your website (upto 10A circuit).
Currently I am using 12-0 transformer and bc 547 for auticutoff and 10k pot for to set cut off voltage.
I set a cut off voltage at 13.5 volt but while setting 13.5v I have faced some issues due to hanging wires now it’s resolved but still 10k pot resolution is very less I can’t able to set exact value simply if I just touch the pot cut off voltage will jump 1v like that.
For example from 13.5v cut off voltage to 13.7v I am unable to set it small rotation will go more than 14v so please let me know how you selected 150 resistor and 10k pot in the design and also let me know by changing this value I can achieve more resolution or not.
And also I have one more query like to set cutoff voltage I am used fully charged lead acid battery is there any easy way
Is there to set the cut off voltage
(In some video they will connect multimeter and they set the cut off voltage but if I connect multimeter it will showing maximum voltage only so I can’t able to set cut off voltage)
In circuit I added one switch (on/off)and one 5A diode(reverse protection)
I am building 3A,13.5v cutoff lead acid battery charger so please help me as soon as possible.
Thanks for sharing your experience and difficulties in making this.
If many times relay not active at a fix voltage level, then adjust the pot some below or some high than 12 v
Keep in mind The step-down transformer is of higher than 12v. you can use 14v or 15 v transformer
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“WOW, I’m so impressed with the circuit diagram! It’s really detailed and helped me understand how to build my own 12v battery charger with auto cut off. I had been searching for this kind of information online for weeks. Thank you so much for sharing this!
Hi,
I designed the battery charger with the 7808 voltage regulator.
How can the 12V relay operate with an output voltage of 8V max and even lower via the 10K pot?
Thanks for your help.
if you want to use 12v relay with the 8V power, it may fail to trigger the relay coil, with 8v Power you should use 9V relay and which type circuit do you wqant to use. Please clear your required circuit design specification.
This circuit diagram is fantastic! I never knew a 12V battery charger could be so simple yet effective. The auto cut-off feature is a must-have for safeguarding my batteries. Thanks for sharing such valuable information!