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:
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:
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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14 comments:
hi I need more than 400ma, what the value for R2 if I use 500ma and 1000ma, thanks
@Anonymous
For 500mA the value of R2 is 1ohm.
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
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 ^.^"
hi,
nice charger but does it cuts off battery voltage when batteries are fully charged. no description given regarding this.
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.
Hi,
I cant see Voltage selection figure.
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.
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.
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!
@alive
What value of resistor R1 and R2 did you used in your circuit?
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.
@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::..
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!
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