Putting rubber tires over top of the tires that are already on a car!

The cell phone already has a charger circuit in it. Adding another charger circuit won't work.

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Uncle $crooge

 

so there's no other way but to change our auto-shut off feature for the cellphone charger... how about an alarm system? the charger alarms when the battery is already full (but i think at no load condition, the charger will alarm, unless theres a load) any good suggestions for our project?

 

Lithium powered cell phones dont overcharge the battery( unless the charging circuit is damaged) if they did you would have a fire any time the battery was overcharged ( it was allready mentioned that overcharging them ,even a small amount, will cause a fire).

All of the cell phones I have seen in the last 5 years have the charger circuit in the phone and that circiut limits the charge. The power supply that plugs into the phone is just an unregulated supply.

sam

 

But how come that there are some cases of overcharged batteries due to unattended charging condition of a cellphone(a fully charged battery is left connected to a wall wart charger)

 

Duff charger circuit?.

How do you know the battery is overcharged?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

as an example, my cell battery(a BL-4C battery for nseries and 60 series nokia phones) expanded its size(looks mutated) and its life span was lessened, i don't have a picture my battery, but i think you can visualized what i've stated.

as for the li-ion batteries for nokia 3310's, i've seen some expanded batteries.

 

Sounds like the charging circuits died then, usually an important part of the charging circuit monitors the temperature of the battery, and if it gets too hot then shuts it down.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

The battery is a Lithium-Ion type. The 3rd contact is its temperature sensor.

Attached Images

Nokia battery cell.JPG (14.2 KB, 7 views)

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Uncle $crooge

 

The only time I have seen or read about repeat problems with lithium batteries in consumer electronics is, from defective batteries (real namebrand ones) or, and these are the most common, bogus, bootleg namebrand or just cheap crap from China.

 

what do you mean by the 3rd contact? is it on the center?, on our charger circuit, will be going to use the 1st and 3rd contacts (indicated with + and -)

 

The temperature sensor is the middle contact but I don't have any spec's on it.

__________________
Uncle $crooge

 

As johnny storm would say... Flame on!

http://www.youtube.com/watch?v=SQ0SN...elated&search=

http://www.youtube.com/watch?v=vE532lRT3kw&NR=1

 

horrible... is it safe to use, 6V / 300mAh charger on li-ion batteries?(3.7V)

 

Of course not!
Then the battery will over-charge and will catch on fire.

You need a Li-Ion battery charger IC that limits the current and stops the charging when the voltage reaches the manufacturer's recommendations.
It has a backup circuit that uses the temperature sensor in the battery to stop charging when it gets too hot.
It has a low voltage detector that reduces the charging current to a battery that has been discharged too low.

The cell phone has this IC inside.

__________________
Uncle $crooge

 

so if we can't avail this maxim IC, can we use at least 3.7V to 4.2V(300maH) specs on our charger circuit?