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Help Battery charging question


Nov 19, 2010
I just started using a charging cradle - the type where the Evo sits in the front and the spare battery lays in the back and they both charge at the same time. My question: is it "safe" to just leave the spare battery laying there charging or does too much charging actually damage the battery? Reason for the question is a comment by a Sprint employee who told me it was harmful to keep a battery charging for too long after it reaches 100%. Thanks in advance for your time and help.
Thanks that was a great explanation! One last question to make sure I understood all of it correctly. Apparently if I charge my battery while still in the phone it charges full, then drains down some to a pre-determined point (by usage) and then recharges it back up again. But what happens to a battery that is not connected to a phone, i.e., one that is just laying in the charger. I assume it cannot be used - so can that particular battery be damaged/catch fire?
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If the charger is properly designed, it's going to do the same thing as when the phone is charging while off. The rollercoaster is much shallower because the battery is only doing what batteries do - slowly discharging over time.

If the charger trickle-charges, the battery can catch fire. They're not supposed to do that. They're supposed to shut off the juice when the battery's charged. So - if it's properly designed, there would be no difference between taking the battery out or leaving it in.

If it's almost properly designed it will overcharge - the battery will feel warmed up after the full charge point, meaning the metal tubes inside the battery are now starting to deform and that will reduce battery life and quality.

If in doubt, watch it on the charger, when it hits green/whatever for that model, see how the battery feels - leave it an hour and see if it's warmer. If it is, the rep was right, and in that case, remove the battery when fully charged.

I mention this not because I'm wrong about the design thing - but because with a lot of accessories you never know where they'll cut corners to save costs.
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