Low Cost Universal Battery Charger

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.

A Low Cost Universal Charger Circuit Diagram:

A Low Cost Universal Charger Circuit Diagram
R1 = 120R-0...5W
R2 = See Diagram
C1 = 220uF-35V
D1 = 1N4007
D2 = 3mm. LED
Q1 = BD135
J1 = DC Input Socket
  • 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 …
  • 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.
To charge a 6V battery a minimum supply voltage of 12V is needed, the maximum voltage is then 15V.
Voltage selection:

Voltage Selection Chart For Low Cost Universal Battery Charger

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.

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.
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.
  • 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.


  1. Thanks a lot for providing valuable information and its very nice post. SINOELE is an well known manufacturer & supplier of Universal Battery Charger, universal mobile power station and portable power charger in China with attractive style and looks in products.

  2. I like the helpful info you provide in your articles. I'll bookmark your blog and check again here regularly. I am quite certain I will learn many new stuff right here! Good luck for the next!

  3. With the help of the circuit diagram you provided , i am going to try it on my own , Thanks
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  4. I want to charge a 2.4v battery pack. I have heard that you should only charge with a little above the voltage of the battery. Like charging a 12v you feed it 14v. So I am surprised that a 2.4v should be charged with more than three times its voltage. Wont that damage the battery?