I decided to replace the LED flashlight, instead of three AAA batteries. The question arose about charging them.
Having rummaged in the Internet I found a bunch of sketches, but with details in our city it’s a little tight.
I tried to charge from the cellular charge, the problem is to control the charge, you need to constantly monitor the heating, it starts to heat up a little, you need to disconnect the charge from the battery, otherwise the battery in the best case, or you can make a fire.
I decided to do it myself. I bought a bed under the battery in the store. I bought a charge at a flea market. For convenience, tracking the end of the charge, it is advisable to find a two-color LED that signals the end of the charge. It switches from red to green when charging is complete.
But you can and the usual. Charging can be replaced with a USB cable, and charging from a computer or charging with a USB output.
My charging is only for batteries without a controller. I took the controller from the old cell phone battery. It ensures that the battery is not recharged above 4.2 V, or discharged less than 2 ... 3 V. Also, the protection circuit saves from short circuits by disconnecting the bank from the consumer at the time of the short circuit.
It has a DW01 chip and an assembly of two MOSFET transistors (M1, M2) SM8502A. There are other markings, but the circuitry is similar to this one and works similarly.
Cell Phone Battery Charge Controller.
Controller circuit
Another controller circuit.
The main thing is not to confuse the polarity of soldering the controller with the bed and the controller with charging. On the controller board there are indicated “+” and “-” contacts.
In the bed near the positive contact, it is desirable to make a clearly visible pointer, with red paint or a self-adhesive film, in order to avoid reversal.
Put it all together and that's what happened.
Charges great. When the voltage reaches 4.2 volts, the controller disconnects the battery from charging, and the LED switches from red to green. Charging is complete. You can charge other Li-Ion batteries, just use a different bed. Good luck to all.
