# How to Make Lithium Charger

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You will need this project when you have an extra mobile battery or you need to charge any lithium, Lithium ion or Lithium Polymer battery.

Maximum current is about 650 milliamps. The circuit is designed for batteries of 900mah or higher. Power source can be a 12v Gell cell (Power panel), or can be powered by a car's cigarette lighter.
I use an old 12v DC wall transformer (800ma or more.)

## Step 1: The Schematic

The Circuit is simple , you will need the following

LM317 variable regulator
2N2222A or any Transistor handles 800mA
2 Capacitors 0.1 uf
1K POT
1ohm 1Watt resistor ( current limitor )

Adjust R4 to the required output voltage
R1 controls the output current

## Step 2: The PCB

Here is the PCB of the project , i have used the "Toner Transfer" method, it's very powerful
and easy .
Using HP Glossy paper and Laser printer gives a good results

## Step 3: Final Step

The complete project after soldering the components
i have used a small heat sink for the LM317 in case of charging a bigger batteries.

## Recommendations

• ### Large Motors Class

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## 58 Discussions

There's nothing wrong with this circuit. It is intended for 2 li ion cells. Just a few notes:
1. Check the voltages of each cell to make sure they are above 3 volts. Do not use this charger if your cells are below 3 volts.
2. If you are charging 2 cells, make sure the voltages match, otherwise charge each cell individually.
3. If you are charging 1 cell, set the voltage (via the potentiometer) to 4.2 (or 4.1 to be super safe) volts before connecting the battery.
4. Check the resistance of the one ohm resistor to make sure it actually is 1 ohm, or charging current may be increased. 1 ohm will yield approx. 600mA
5. The battery will never fully charge. As the battery charges, it draws less current. So if your voltage is set correctly, you should have no problems with overcharge.

3 replies

Hi Secret so one can do a pot instead 1ohm resistance to increase or decrease current? Thanks

Hi,

So I'm building a single-cell charger for a 750mAh battery. What are the equations governing the selection of R1? I'm using a PN2222A transistor. I have the circuit set to output a 4.1 load voltage at the moment. I'm just trying to figure out how to limit the current to 750 mA.

Hi, would this work or be able to be modified to work with a 48 volt
battery? I want to make one from 12 Lion 18650 batteries wired in
series. Thanks.

Would it be wise for R1 to be a variable resistor to adjust current? Thanks.

quicker cheaper way to make lithium charger--take apart a camera lithium charger or old cell phone and add red and black wired clips.Bingo--charges any single/double series 3.7 batteries. These units are easily found at Goodwill ect or old Canon cameras.

For those looking to build lead acid charger--here is old timers easy build unit that charges and di-sulfates them.called: Capacitor charger. Check it out on You tube. It just might work out on Lithium if you down scale the input voltage but needs a timer.

R2 and R3??? What are their value ohms or kilo ohms..

You can use 12 parallel resistors. Wire is also OK, because inductance is not an issue here (this is a DC circuit), however you will need to use 4 wire method to measure the resistance precisely.

Could this me adjusted to handle a 15 amp charge. I put together a small lithium pack that is 3.7v at 15amp hours, I would like to charge it at a resonable rate, I was thinking of just regulating the voltage to 4.1 and letting it go.

2 replies

You would have to either get a bigger version of the LM317, I know there's one that'll handle 5+ amps. Or check the datasheet for the lm317, there's some circuits in there. ;)
What do do you need a 15amp lithium pack for anyways? lmao, just wondering.

Would work with a 7805 regulator? Or without a regulator chip?