Simple charger for cell phone battery

[Boncuk]

Here's the problem:

The Motorola C391 cell phone has a real tiny receptacle for the charger which quit after four months of usage. Sometimes the battery charged, but mostly it didn't charge at all.

The "Chang" (Master) of the repair shop did the rest for a null function receptacle. There is no spare part to get.

The battery used is a 3.6V LI-Ion battery. No capacitance is printed on the battery pack. However the original charge adapter has an output voltage of 6.25V at 350mA. Using this the exhausted battery was fully charged within 90 minutes.

Anybody having had the same problem and solved it by building an external charge circuit using the charge adapter?

BTW: None of the batteries has a built in connected temperature sensor. The pin reserved for that is simply connected to ground.

Thanks

Boncuk

 

[Diver300]

There are various Li-Ion and Li_Po chargers. I have used a L6924D but they are only surface mount so not easy to use.

All chargers seem to follow the same rules:-

Do not charge when bellow 10 deg C or above 40 deg C
Charge very slowly if less than 3.2 V
Limit voltage to 4.1 or 4.2 V
Stop charging when current falls to 1/20th of max current.

I think that the most important rule for most of the time is the voltage limit.

 

[roltex_rohit123]

in India We use a special universal charger called khekda (meaning crab) charger. this charger has a adjustable connector which can charge any cellphone battery (samsung, nokia, blackberry etc etc). it even costs very low Rs. 60 ($1.2). its output voltage is 4 - 4.1 and current is 200-300mA. it takes 2 hrs to charge a battery of 1000mah. google for the said name to know wht it is called in your local market.

 

[large_ghostman]

There are various Li-Ion and Li_Po chargers. I have used a L6924D but they are only surface mount so not easy to use.

All chargers seem to follow the same rules:-

Do not charge when bellow 10 deg C or above 40 deg C
Charge very slowly if less than 3.2 V
Limit voltage to 4.1 or 4.2 V
Stop charging when current falls to 1/20th of max current.

I think that the most important rule for most of the time is the voltage limit.

thank you for the info i am building a bot that uses cell phone bats and the info will help alot
lg

 

[roltex_rohit123]

you have to maintain the limit of 4.2 volts for lithium bateries. also dont connect them in parallel while charging due to their high curent density. charge should not exceed to 1x value of capacity