rafiki121 said:
Am i suppose to discharge this battery all the way to 0% then charge it again to recalibrate it?
Palmetto Fellow said:
PGR advises against this. These batteries should never be subjected to a full drain. If the voltage drops below 3V, bad things can happen.
There are two things you just
DON'T want to do to LiPo batteries: Overcharge them and over
discharge them. Corporate lawyers and hardware engineers are painfully aware of this so they build safegards into rechargeable electronic devices to prevent consumers from doing either one. The Evo is an expensive and sophisticated electronic device so it's safe to assume that it's
not an exception. In other words, I'm absolutely convinced that it isn't possible to overcharge or over discharge the Evo battery as long as you leave it in the phone.
An Evo battery is fully-charged when it reaches 4.2V and the phone isn't going to let you exceed that. Discharging the Evo battery below 3.0V will do irreversible damage to it so the phone isn't going to let you do that either. Actually, the reports I've read say the Evo shuts itself off when the battery drops to 3.5V and that sounds about right becase for all practical purposes a LiPo cell is "empty" when it reaches ~3.5V at low discharge rates. This is illustrated quite nicely in
this discharge graph of an OEM 1500mAh Evo battery which was discharged at 250mA with a battery analyzer.
So in theory the Evo's battery "gauge" should read 100% when the battery voltage is 4.2V and 0% when the battery voltage is 3.5V and that seems to be pretty accurate when everything is working right. But something apparently happens to some phones which throws that battery gauge off. I'm convinced that 4.2V is still full, 3.5V is still empty, and the phone will still run for the correct amount of time despite what the gauge says, but the gauge shows a lower percentage than is actually available and that makes people
think the battery is going dead before it really is. Please note that the last sentence is hypothesis based on the anecdotal evidence that I've read in this and other forums about the Evo, but my own Evo has yet to exhibit the behavior so I haven't had the opportunity to confirm it.
Regardless, there is a procedure which apparently recalibrates the the battery gauge and it does involve discharging the battery until the phone hits the low-voltage cutoff. That's
not all there is to it, though, and your phone needs to be rooted so you can delete the battery stats. The procedure I'm talking about can be found
HERE in Section 2.4 "Battery Recalibration". I haven't done this procedure because I haven't had to so I can't comment on how successful it is. You can also find other procedures without looking too hard, but Cyanogin's is the only one I've seen that doesn't read like an ad for snake oil.
Pete