Low Cost Universal Battery Charger Schematic Circuit Diagram

Low cost solution for charging of both NiCd and NiMh batteries

Here is the circuit diagram of a low cost universal charger for NiCD - NiMH batteries. This circuit is Ideal for car use. It has ability to transform a mains adapter in to a charger . This one can be used to charge cellular phone, toys, portables, video batteries, MP3 players, ... and has selectable charge current. An LED is located in circuit to indicate charging. Can be built on a general purpose PCB or a veroboard. I hope you really like it.

Picture of the circuit:

A Low Cost Universal Battery Charger Circuit Schematic For NiCD and NiMH

A Low Cost Universal Charger Circuit Schematic

Circuit diagram:

A Low Cost Universal Charger Circuit Diagram

Parts:

R1 = 120R-0...5W
R2 = See Diagram
C1 = 220uF-35V
D1 = 1N4007
D2 = 3mm. LED
Q1 = BD135
J1 = DC Input Socket

Specifications:

Ideal for in car use.
LED charge indication.
Selectable charge current.
Charges Ni Cd or NiMH batteries.
Transforms a mains adapter into a charger.
Charge cellular phone, toys, portables, video batteries …

Features:

LED function indication.
Power supply polarity protected.
Supply current: same as charge current.
Supply voltage: from 6.5VDC to 21VDC (depending on used battery)
Charge current (±20%): 50mA, 100mA, 200mA, 300mA, 400mA. (selectable)

Determining the supply voltage:

This table indicates the minimum and maximum voltages to supply the charger. See supply voltage selection chart below.

Example:

To charge a 6V battery a minimum supply voltage of 12V is needed, the maximum voltage is then 15V.

Voltage selection:

Voltage Selection Chart - Low Cost Universal Battery Charger Circuit Diagram For NiCD and NiMH

Voltage Selection Chart For Low Cost Universal Battery Charger

Determining the charge current:

Before building the circuit, you must determinate how much current will be used to charge the battery or battery pack. It is advisable to charge the battery with a current that is 10 times smaller then the battery capacity, and to charge it for about 15 hours. If you double the charge current , then you can charge the battery in half the time. Charge current selection chart is located in diagram.

Example:

A battery pack of 6V / 1000mAh can be charged with 100mA during 15 hours. If you want to charge faster, then a charge current of 200mA can be used for about 7 hours.

Caution:

The higher charge current, the more critical the charge time must be checked. When faster charging is used, it is advisable to discharge the battery completely before charging. Using a charge current of 1/10 of the capacity will expand the lifetime of the battery. The charge time can easily be doubled without damaging the battery.

Note:

Mount the transistor together with the heatsink on the PCB, bend the leads as necessary. Take care that the metal back of the transistor touches the heatsink. Check that the leads of the transistor do not touch the heatsink.

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28 comments:

Anonymous [Reply]: hi I need more than 400ma, what the value for R2 if I use 500ma and 1000ma, thanks; 04 November, 2009
Webmaster [Reply]: @Anonymous

For 500mA the value of R2 is 1ohm.; 08 November, 2009
Jason [Reply]: Hi, your charger is very interesting and I'm going to build one. I would like to know how to read the Voltage Selection Chart, I would like to know, if I want to charge a 1.2V battery I chose which battery voltage the 1.2v or 2.4V also for 9V battery do I chose the 9.6V or the 10.8V.
Thanks; 19 November, 2009
K3nZoR [Reply]: I got a 6V 120mA nicad battery pack and i wanna charge it, i got a regulated 12V 1A power source, the walue of r2 shud be the one for 100mA or do i need another value for it ? btw sorry for my dumb question but im new 2 electronics ^.^"; 23 November, 2009
vijay [Reply]: hi,
nice charger but does it cuts off battery voltage when batteries are fully charged. no description given regarding this.; 05 December, 2009
Anonymous [Reply]: Cool man, This rocks.
I like the idea.

Vijy my man, Use a pulse triger to cut off the power once the battery is fully charged. Or USE a simple timer.; 11 December, 2009
Anonymous [Reply]: Hi,
I cant see Voltage selection figure.; 15 December, 2009
Tahir [Reply]: I want to build this charger to replace charger for my drill machine. My charger died few days ago. Can you please post PCB layout also for this project. I will use spare power supply for my old printer for this which has 18V.; 24 December, 2009
yongsik [Reply]: Great circuit!
I had made it with this circuit.
There are general, cheap and simple circuits. Furthermore, it is good working.
I have been satisfied in it.
Thank you, Izhar Fareed.
I will wait your simple and wonderful circuit.; 01 January, 2010
alive [Reply]: I want make a 1.2V battery charger but when i simulated this ckt on Multisim, it showed tht it wld require 5V supply and R1 and R2 should be in Mega Ohms to give the required output. Can any1 plz help me by telling which resistances shall i use? Plzzzzzzzzzz its urgent!; 05 February, 2010
Izhar Fareed [Reply]: @alive
What value of resistor R1 and R2 did you used in your circuit?; 06 February, 2010
alive [Reply]: When I kept R1=2100M ohm and R2=1800M ohm then the simulation showed an output of 1.2V. I doubt this simulation but don't know what resistances shall I practically use.; 06 February, 2010
Izhar Fareed [Reply]: @alive
I don't understand that why did you used R1=2100M and R2=1800M. You should use R1=120 ohm at (0.25W) and R2=47 ohm at (0.5W) for your desired output voltages and current as shown above in parts list and in diagram. Minimum input voltages will be 6v and the max will be 10 volts.
..::Best of Luck::..; 06 February, 2010
alive [Reply]: I used these specifications but the simulation didn't show the expected result. Thnx a lot for ur reply and i would use these resistances in ma hardware and hopefully there must have been some error in the software or in simulation. Thnx agayn!; 07 February, 2010
Anonymous [Reply]: Hello All!

I have only a question: The LED will light up when the battery is full or during the charge?

Thanks in advance!; 23 March, 2010
yongsik [Reply]: Hi "Anonymouse. said..."
This "Low Cost Universal Battery Charger Schematic" is simple and having a hidden logic that you does not know something.
The LED will light up when the battery is charging. (But, there was no charging cut out circuit); 31 March, 2010
Santo [Reply]: I am also thiking abut giving it a try.... thanks....; 11 May, 2010
de-facto7 [Reply]: Nice circuit. I use it for 12V and smaller but I have a 14.4V (14 to 16V) NiMH I use for my solar tracker. Is there a mod that will allow the extra voltage? There is a voltage leak if I try to charge those batts... I think. I'm no expert but the LED is on when the 14.4 is hooked up and there is no power input connected. I am using a 3.9ohm for R1 and the input voltage is 20.5 to 22V depending on solar conditions.

Thanks; 06 October, 2010
de-facto7 [Reply]: I decided to put a voltage divider on the input to the charger to lower the voltage to between 16 and 18V. That took care of my problem since my panels are putting out 20 to sometimes as high as 23V that was just too much. All is well. I also need to correct myself in my last post. The LED was on WITH the panels connected and the negative lead to the battery was connected as well... with or without the positive lead. Weird...; 08 October, 2010
raudhah_collection [Reply]: hi I need more than 400ma, what the value for r1 and R2 if I use 1000ma,2000ma,and 5000ma, thanks; 26 December, 2010
KenChia [Reply]: I'm using 9v 175mAh NiMH battery. Can I use 12V 400mA adapter?; 26 March, 2011
Izhar Fareed [Reply]: @KenChia
Yeh! You can use 12V-400ma adapter.; 27 March, 2011
KenChia [Reply]: thanks alot...it helps; 27 March, 2011
shivam.d [Reply]: Um I am a kid and my r/c ufo uses 8 batterys (aa 1.5v) in its chargerso so about 12v to charge for about 15 minutes. I want to make a plug in charger for it. I have the charger itself and a plug but I am not so good at the extra sciency stuff cos i am 12. Got any advice? HELP!!! please!!! Thanks....; 22 May, 2011
deepak kapila [Reply]: Hi,

I want to make a charger to charge a NiMH battery pack of 6V/2400mAH with a solar panel of 1.8W/6V kindly let me know the schematic for the same as we will require a boost circuit for the same.

Thanks; 10 September, 2011
AUTOMOBILE [Reply]: How can i charge 12v 70ah battery; 27 October, 2011
AUTOMOBILE [Reply]: Concerning the relay, pls explain the pins, and how to connect the pin to regulator and the output of the inverter.; 01 November, 2011
GKN [Reply]: Plz post the voltage cut off circuit; 19 November, 2011