DIY 3.7V BATTERY CHARGER WITH AUTO CUT & LED INDICATOR

So Hey guys in today's article I am going to teach you how to make 3.7 Volt Lithium ion or LiPo battery charger circuit

Lithium ion or LiPo batteries are very popular, especially with makers like.

These batteries are also very sensible and dangerous. If you don’t control the process of charging of such batteries, they will stop working or worse. The battery can swell and even explode from overcharging, and a deep discharge can make the battery fail.


Components Required:
  1. BD140 Transistor
  2. Resistors: 1k, 20k*2, 330R,
  3. TL431 Shunt Regulator
  4. 1N4007 Diode *4
  5. 20K Trimmer Potentiometer
  6. Red LED
  7. 2 Pin Terminal Block
Circuit Digram:

3.7V BATTERY CHARGER WITH AUTO CUT & LED INDICATOR

We have a PNP transistor connected in series with 4 diodes that will simulate a load. At the base of the transistor, we have a Zener reference diode (TL431) which will get open at a certain voltage value and by that connects ground to the transistors base and when the transistor is active, we bypass the battery and waste the power on the diodes instead. This ZENER diode is the TL431 and it has a reference pin, so by adjusting the potentiometer we can set this reference to be at 4.2V, that’s how we select when the charging process will stop.

Before understanding how the circuit works, let me tell you that I am using custom-made PCB to make this circuit. This project is sponsored and supported by JLCPCB

https://jlcpcb.com/IUP

I am giving you the GERBER file so you can download and use it for free. For PCB orders you can use JLCPCB You can order your custom-made PCB From JLCPCB If you are a new user register on the website through our link: https://jlcpcb.com/IUP and you can get a $54 new user coupon code that you can use in your first order shipment and SMT service. I would definitely say to use this coupon code.

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How it's work?

I supply it with 4.2V from my power supply. I connect my multimeter at the output and using the potentiometer, we first fix the threshold value to around 4.2V, I will use a battery which is discharged and below 3.90V When I connect it to the charger, the LED is turned off. Now the battery is getting charged up. After some time, when we get above 4.2V the LED will turn ON so the charging process is complete. Current is now flowing through the diodes and transistor and we skip the battery, so the cell is protected for over voltage.

I measure battery and it is 4.1 volts.

3.7V BATTERY CHARGER WITH AUTO CUT & LED INDICATOR



Hope the article helped you.

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