Introduction: How to Make Lithium Charger

Picture of How to Make Lithium Charger

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

Picture of 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
1ohm 1Watt resistor ( current limitor )

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

Step 2: The PCB

Picture of 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

Picture of 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.


secretsather (author)2011-04-02

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.

guruji1 (author)secretsather2016-09-20

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


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.

can we make this charge 1or 2 amps remaining adjustable from 4.1 to 7.2?

Yaleh (author)2017-06-29

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.

guruji1 (author)2016-09-14

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

GeorgeA99 (author)2016-08-15

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.

Smoog (author)2016-03-11

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

DavidM500 (author)2016-01-17

I'm not getting any current draw when adding the battery in. Any ideas?

ThijssjihT (author)2014-07-23

I don't have that 1W resistor. Can I use a bit of constantan wire, or will that create to much inductance?

ThijssjihT (author)ThijssjihT2014-07-23

Or can I use 12 parrallel 12 ohm 1/4 watt resistors?

glitvjaks (author)ThijssjihT2015-05-06

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.

snowluck2345 (author)2011-10-02

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.

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.

You could also put several 317s in parallel to bump the current capacity, if you are unable to find a larger regulator.

Imetomi (author)2015-03-25

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

I dont think so. A 7805 is a 5v regulator, and a 317 is a variable regulator. The adjustable part comes in when you need to fine tune the set voltage, otherwise, you risk cooking the batteries.

Electrolight (author)2014-04-10

I just wanted to forworn everyone. This is a nice simple charger but it does not balance. As such, after a while your lithium battery's charges may drift from one another until burnout can occur. This does take quite a few cycles, but if you are using larger batteries or high quality expensive ones, I would excercise caution.

kavee123 (author)2014-01-09

R2 and R3 ????

aali33 (author)2013-10-23

Dear, I want to help you to prepare a good lead acid battery charger. Skype: "zaheerulhaq3"

wcheng2 (author)2011-07-04

Can someone please explain to me what the purpose of Q1, C1, and R1 are? Why does R1 need to be rated at 1W?

kool1zero (author)wcheng22013-06-26

Q1 is a transistor, that allows you to adjust the level of something going into one with another component. different types work for different applications.

C1 is a capacitor, from what I can tell, it is keeping the values from spiking and just leveling out.

R1 is a resistor. It needs to be rated at 1W to make sure that it overheats

kool1zero (author)kool1zero2013-06-26

it doesn't overheat*

claudiopolis (author)2012-09-29

Dear Sir, you should have at least mention Scott Henion as he designed this circuit. His page and circuit is here:
Much better explained.

hosam_eldin (author)claudiopolis2012-11-12

Hi claudiopolis,

Thanks for the comment, i totally agree with you
I will add it, please give me some time, i'm very busy thses days

Thanks a again

ayasashii (author)2012-10-31

Salam brother Hosaam

I wanted to write in Arabic so that you can understand me well,
I liked your projects and I translated them as well
please contact me since I wanna explain what I have in mind to you.
this is the email address:

my name is Sahli

ayasashii (author)2012-10-31

السلا م عليكم أخينا حسام

لقد أعجبتني مشاريع البسيطة الشرح لذلك قمت بترجمتها لكي تكون متوفرة للناطقين بلغة الضاد.
اسم الموقع الذي ننشر فيه مثل هذه المقالات يحمل اسم اصنعها
إذا كانت عندك مشاريع أخرى تريد نشرها فأرجوا أن ترسل إلينا عبر بريدي موقعنا وهو

أرجوا أن تتصل بنا فنحن في حاجة إلى أمثالك في أمتنا.
شكرا لك.

spooge (author)2012-03-25

it is possible to charge a 12V SLA battery with this circuit?

applejuice1998 (author)2012-03-12

I just made this circuit, with 1/8 watt resistors ( except for the 1 watt one )
& I'm just wondering how this circuit works. What's the purpose of Q1? I know what the regulator does, just confused about Q1.

max308 (author)2012-02-21

I am wondering will this circuit works for 12V Li battery?

fordb91 (author)2011-11-06

can i use BC548 or 9014 Transistor?

ahdai (author)2010-11-14

Never charge a lithium cell with a constant current. It is only a matter of time you forget and the cell gets overcharged and bloat.

There are many ICs designed for that purpose. 1555 1811 etc...

Sandisk1duo (author)2009-07-08

does it turn off when the battery is fully charged?

jimtran93 (author)Sandisk1duo2010-01-23

 No it doesn't. This charger is very basic.

spike2fei (author)2009-09-30

is there a way to make a charger control for acid led battery it will help me to thanks

shawnsoucy (author)2009-05-09

can you use this charger to charge capacitors

lolzertank (author)shawnsoucy2009-07-03

Capacitors are very easy to charge, just hook them up to a voltage source with a resistor in series.

rc jedi (author)2007-09-10

over voltage condition=fire
over current=fire
out of balance condition=fire
overdischarge=damaged battery

use a real charger

ReCreate (author)rc jedi2009-01-18

laziness = fire
not waching the battery =fire
being stupid = fire

hosam_eldin (author)ReCreate2009-01-19

Thanks from your language, you gave much about yourself

ReCreate (author)hosam_eldin2009-06-24

Laugh out loud, I was joking you know

ReCreate (author)hosam_eldin2009-01-21


trialex (author)2009-03-05

Why not use a simple controller chip that is DESIGNED for Li-Ion batteries? The MAX1555 is designed to prevent over-charging of Li-Ions, and it needs LESS support components than this design.

samkim (author)trialex2009-05-13

Hi Friends, I am new to this forum, well I am trying to make a Li-Ion charger using Max 1555, has any one tried out doing this, if so please do tell me, I have been unsuccessful many a times doing this experiment. I am enclosing the circuit used for this experiment.I have done all the circuit connections as shown in the diagram but still when the battery has been charged after being discharged till 3.55V, while charging the LED will be in ON state, when it reaches the maximum(4.15V), the LED has to turn off, but in my case it remain to be ON. Could any one know the exact reason behind this.I am using DC input instead of USB for charging.Is it okay with it.Thank You.

rob_fed (author)2008-12-15

I need a simple current source like this, not necessarily for li-ion batteries, I was wondering if the Q1 could be replaced with FET like and IRF511?

Keso (author)2007-09-10

While I'm not an expert on battery charging, especially with lithium chemistries, what I have read about them so far suggests that an overly simplistic approach to charging lithium cells such as described here will more than likely damage your batteries and quite possibly cause a fire / explosion.

This circuit may work fine for lead acid batteries but, for lithium, you're quite literally playing with fire.

I *strongly* advise anybody considering making this circuit to do their research on lithium battery chargers first.

Myself (author)Keso2007-09-17

Absolutely dangerous if left alone. A current-limited, voltage-limited supply will work for the bulk charging phase, but this design requires that you manually monitor charge current and terminate the charge at the appropriate point. Allowing current to "trickle" in past the termination point will plate out metallic lithium on the electrodes, and detonate the cell.

Powerstream has a good how-to on charging lithium-ion batteries, which I've done by hand successfully many times. It takes an adjustable power supply and two meters, so you can monitor voltage and current simultaneously.

The circuit detailed here will cap the voltage, and if you use it with an appropriately small wall-wart that'll limit the current too, but you still need to monitor the current drop and disconnect the charger manually. Leaving it connected will destroy the battery, period.

klee27x (author)Myself2008-09-15

Actually, leaving it connected is a bad idea, but if the voltage is regulated properly, just a hair below 4.2V, this should ensure some degree of safety. To ensure that the voltage of an LM317 circuit does not float high at very tiny loads... such as when the cell is fully charged, you ought to add a small load resistor to the LM317 output. An indicator LED is sufficient. If your battery is trying to pull too much current, you can dither add a power resistor in series, or you can charge it in stages. I.E. set the voltage to a midway point between the cell and 4.2V. After a while, bump it up to 4.2V. Use as many incremental stages as necessary for the size/ESR of your battery. For multi/cell batteries, you can certainly get a voltage mismatch between cells. This occurs because as cells die, the voltage they accept starts to get lower. So a 4.2V cell will no longer hold 4.2V... it might be 4.0V. So if you are charging an 8.4V 2-cell battery, the good cell is now being exposed to 4.4V. I've had this occur a couple of times. If you do not catch this, you will permanently damage the good cell, too. *To all the experts who have seen Kip Kay videos and other vids of li ion cells being connected to 2 car batteries in series or thrown in fires- thanks for sharing your knowledge. We all feel smarter for it.

klee27x (author)klee27x2008-09-15

Oh, and I wouldn't use a cheesy trim pot. Use a high quality potentiometer or fixed resistors to ensure a stable output voltage.

gege (author)2008-09-09

This little charger is a NICE , SIMPLE way to charge li-ion batteries . It has a current limiter , change R 1 value to adjust to your needs It has a voltage limiter (it should be adjusted with NO load to 4.1 volts ) What else ?? a timer ... a thermal sensor ? a micro processor ? a Pic can do all that..

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