1.2V lithium Battery charger with LED monitoring circuit

[tengyy]

Can someone suggest me a simple 1.2V lithium Battery charger with LED monitoring circuit ?
wish the LED can indicate fully charge and stop
and charging state LED

 

[Audioguru]

A Lithium battery cell is charged to 4.20V then it slowly discharges to 3.2V when it should have its load disconnected. Then its average voltage is 3.7V.
Maybe you have a Ni-Cad or Ni-MH cell that averages only 1.2V, but is charged to 1.4V or 1.5V?

Simply use a battery charger IC made for the type of battery cell you want to charge. You cannot simply measure the voltage because the voltage rises fairly quickly during charging but the cell is no where near fully charged because it is still charging with current.

A simple Lithium charger circuit can cause your home or car to burn down because when charged wrong a Lithium cell catches on fire. Lithium is a very active metal like magnesium (used in flares). The fire is very hot and is difficult to stop. Water on it makes it burn hotter.

 

[--BawA--]

need some more info
What is the mAh rating of your battery?

 

[tengyy]

need some more info
What is the mAh rating of your battery?

some is 1200mAh, some 3000maH

 

[Audioguru]

Why do you say your "lithium" battery has a voltage of only 1.2V? Is it a Ni-Cad or Ni-MH battery instead??
Or is it really a lithium battery with an average voltage of 3.7V, not 1.2V??

 

[tengyy]

it is AA or AAA Nickel-cadmium battery

 

[Audioguru]

A Ni-Cad battery is old. American battery manufacturers do not make them anymore because cadmium is an extremely toxic deadly metal.
Ni-MH batteries are much better and replaced them. Chinese products still use Ni-Cad rechargeable batteries (solar garden lights for example).

If your old Ni-Cad cell still works (an old one is usually shorted inside) then it can charge from a Ni-Cad charger until its voltage measures 1.4V to 1.5V then it is fully charged.
You can find many Ni-Cad charger circuits in Google, some work and others don't work.

I have two very cheap Ni-Cad or Ni-MH chargers made by American battery manufacturers. One simply charges up to 4 cells all the time. Put dead cells in it at night and take out the charged cells in the morning. If you do not remove the cells then it overcharges them that reduces their life. The other charger charges up to 4 cells with a timer that shuts off the charging after 6 hours. It overcharges cells that were not completely dead.

A charger has a limited voltage of about 1.5V and a current limiter. An overnight charging current is usually 1/10th its mAh rating.