Auto Cut off 3.7 volt Battery Charger Circuit | How to make 3.7 volt Battery Charger

How to make Auto Cut off 3.7 Volt Battery Charger:

So hey guys welcome back to a new article after a long time I come back with a new article and with a new circuit.

So today's article we are going to make Auto cut lithium-ion battery charger circuit. By the way last year I made a circuit that can charge a lithium-ion battery and after a full charge, the indicated green LED and on the charging time circuit indicate red LED but there was a problem with that circuit there was no auto cut option. 😳

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What happens if Lithium battery does not have a auto cut option??

If you are charging a lithium-ion battery and the circuit doesn't have the auto cut option then it is dangerous. Because the circuit only indicates that your battery is fully charged. now, this is your responsibility to remove the battery after full charge because that circuit doesn't have auto cut option. It will continuously charge the battery even after the green LED will be glowing This thing makes it dangerous. & If you forget for a long time battery can explode at any time.

So that's why I make an upgraded version of the previous circuit and it's come with an auto cut option. This battery charger circuit provides the automatic cut off the facility when the battery gets fully charged.

So what are you waiting for..???

let's see which components we need for making this auto-cut lithium-ion battery charger circuit. For building this project, the below components are needed. These are easily available in the market.

Components -:

  • BC547 Transistor or Any NPN Transistor
  • 10K Resistor
  • 1K Resistor *2
  • 10K Preset
  • 10Uf 50V Capacitor
  • Red & Green LED
  • 5V Relay
So for making an Auto Cut lithium and battery charger circuit I am using a custom-made PCB, PCB makes work easier just you have to put all components and After Soldering all these components and you are ready to use this circuit.

Circuit Diagram

By the way, you can order your custom-made PCB From JLCPCB If you are a new user register on the website through our link:, and you can get a $30 new user coupon code that you can use in your first order shipment and SMT service. even you can get a $24 coupon code every month after you placed your first order. That you can use in your SMT service and if you follow the Facebook page then you can get it $10 coupon code once again you can use in your SMT service. There are so many coupon codes available so I would definitely say to use these coupon codes.

Download Gerber File Here 👈

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Working of Auto Cut-Off Battery Charger Circuit:

Before the use of the circuit, you need to adjust the auto cut-off voltage range for the auto cut This adjustment is done by the 10k preset and a multimeter connected with the output terminals that go to the battery. First, you have to give the power supply in the circuit and move the preset till the green LED is ON. Once the auto cut voltage is set the circuit is ready to use.

In the above circuit, whole charging is driven by BC547 Transistor and relay during charging the circuit takes Input form charger circuit shown above.

After the battery reaches a certain level the transistor BC547 is Tuned ON and it's driving a relay that turns on and changes the COM pin's Link from NC to NO which is connected to the Green LED that will start glowing after the relay change over indication the battery charging completion.

Watch YouTube Video:

Here is a video watch the video till the end you will understand everything.

By the way don't forget to visit the JLCPCB website and order your custom made PCB at $0 new users register on the website through our link:, and you can get a $30 new user coupon code that you can use in your first order shipment, and SMT service.

Download Gerber File Here 👈

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