[dancing-bass]

OK, so my specific device is a GSM Galaxy Nexus. But I'm asking here because I'm thinking the answer may help other people too

So, I have 3 batteries for my phone. 1 stock (1750mAh) and 2 extended (2000mAh). No I don't need all that juice... its a story for another time. Anyway....

Lately when I charge a battery in the external charger (using a USB cable and the wall plug supplied with the phone) the battery will not fully charge. The LED on the charger will change from red to green (Usually I charge the battery overnight, or while I'm away at work during the day). However when I put the battery in the phone, it will show somewhere between 80%-90% charged.

1) Would a 100% drain and charge reset the battery's "fuel gauge"?
2) My phone automatically powers off at 6% (which is fine, needs enough juice to save current settings and power down properly). Is there a way to truely drain the battery down to 0%? (I'm thinking of some kind of low-voltage lightbulb or LED connected to the positive and negative terminals should drain that down to 0%. Is this recommeneded or is it fine just running it down till the phone powers off?

Normally I try to plug my phone in and charge (or power off and swap batteries) once they hit about 40%-60%. I'm only interested in doing a full drain to see if that will get these batteries to fully charge in the desktop charger. Besides I've read from a few sources that it is GOOD for the battery to do this once in a while (Fully drain, charge to100%) to properly maintain them.

And as a side note, charging the battery in the phone (either with the wall plug or from USB cable on my computer) will always result in a 100% charge, which makes me thing the issue is with the desktop unit itself (perhaps faulty circuit that cuts off charge current when it thinks its full ?)

[Mooncatt]

From what I've heard around here and other places is it's not good to take a Li-ion battery all the way to 0%, which is why devices shut down just before then. I can't really help you on the other points, but i wouldn't try the light idea to take it all the way down.

[Rukbat]

1) Once you take a LiIon battery down to 0%, unless you have a good battery lab, what you have is toxic garbage that you can't just throw out with household garbage. LiIon batteries have a protection circuit that disconnects the battery from the terminal if the voltage falls too low (charging it could cause an explosion), and that can only be reset with a pretty expensive piece of equipment.

2) Always condition a new battery. Charge it fully (to 100%) before using it. Use it until the phone shuts off before charging it again. Do this cycle 3 times.

3) From what you've described, I'd say either that the charger is defective, or it charges to about 90%, then tops the battery off. Try leaving a fully discharged (phone shuts off) battery in the charger for about 48 hours. If that doesn't bring the charge to 100%, I'd say the charger is defective. (Leaving a LiIon battery in the charger for a few days won't harm either the battery or the charger.)

[ts1898]

I have a similar issue with my Galaxy S3 battery in the Kidigi charger cradle, it only charges to 85% even after an all night charge. This is if I charge it in the allocated rear slot, it does fully charge if it's charged in the Galaxy S3 phone. I wish someone could shed some light on this. Could this be an issue with the Kidigi charger?

[Rukbat]

There are about 3 "end of charge" indications for a LiIon battery. Cheap chargers monitor only 1 of them - terminal voltage. The battery will get to "fully charged" terminal voltage before it's fully charged, so if that's all the charger is monitoring, it'll shut off when the battery isn't fully charged. So yes, it could be an issue with that charger.