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Old 10-11-2012, 08:43 AM   #16
knc1
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Posts: 6,222
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Join Date: Feb 2012
Device: Too many.
Quote:
Originally Posted by Popup View Post
I tried again to see if I could revive it. I charged the battery (using a bench power supply, set to 4.1V, current-limited at 150mA) for about an hour last night. (I would have left it longer, but at the same time I didn't want to leave it over night.) It looked like the battery retained some charge, as the terminal voltage rose from 3.6V to 3.74V. However, this morning it was down to 3.55V (I left the battery in the kinde.)

My guess is that there's some short-circuit somewhere that drains the battery faster than the internal charging-circuitry can charge it. I have had a look at the accessible parts of the PCB, but I can't find any tin-whiskers, dust-motes or anything like that. I might try to flush it clean with compressed air and-or PCB cleaner, to see if that dislodges something. But if that fails I think I've got a broken PCB on my hands.

At the same time, I'm less and less inclined to spend much more time on it, as my Paperwhite should arrive in a couple of weeks.
The internal charger can control a 30% charge rate (500ma).

Consider first that you have an over-discharged battery. It was at least one time in its life, over discharged.
The failure mode for this type of battery is lose of charge capacity, not loss of ability to charge to its rated terminal voltage.

Remove battery ;
Charge at a 10% rate (150ma) for at least 12 hours ;
Check terminal voltage (when good (above 4.1v), then) ;
Disconnect battery ;
Check its room temperature, self discharge rate (over a couple of days) - it should not have a noticeable self discharge rate over a matter of only a few days ;
Fully recharge ;
Check its room temperature, 1 hour discharge rate, being careful to not let it discharge below 1/2 its (2.2 volts) full-charge terminal voltage.
If it reaches its test limit discharge level (2.2 volts) in less than 30 minutes - it is junk.

The above should qualify the battery as "good" or "time to replace".

Note:
Stop with the cleaning and searching for leakage on the board, you are more likely to do harm than good.
Whatever gave you the idea that a Kindle has a power-off switch?
If it has power applied, at least some parts of the board's electronics is "running".

PS:
It you are tired of playing with it -
Any chance you would like to sell it, as-is, and what part of the world do you live it?
PM me about that.
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