This is EXACTLY what's the problem. That's it.It has nothing to do with live wallpapers, nothing to do with apps running in the background, NONE of that. It's 100000000% because the phone stops charging once it reaches 100% and starts using the battery for power. I recently bought $10 kit that comes with 2 battery and a wall charger. Putting the OEM battery on the wall charger overnight has proven this to me. This morning immidiately after putting the bat back in the phone I browsed online, checked engadget, tweeted, checked email all for a total of about 15 minutes. Still stayed at 100%. Usually it would be at about 80-85% by then. I'm getting close to 20hrs of medium to heavy use now because the battery is getting a legit full slow charge.
That is incorrect.
Once the phone charges to what we read as "100%," the phone
does not begin to run off the battery.
What is happening is that as the battery reaches a charge of 4.2 VDC (maximum safe), the phone stops charging the battery as storing a Li+ battery at full charge significantly reduces it's lifespan. The charging circuitry powers the phone and charges the battery in parallel. The phone is not running off the battery alone.
The effect you're seeing is that a Li+ battery cannot maintain a maximum charge for very long. So while the maximum capacity of the battery is 4.2 V, it's nominal voltage is down around 3.8 V. So, without being charged, the battery will slowly discharge on it's own toward a voltage closer to it's nominal voltage. If there was a problem, the discharge wouldn't level off as it does. That 7 - 10% you lose in the first 20 minutes would continue and the battery would die in under two hours.
This is why removing the charge and re-applying it is effective. By removing it and returning it, it resets the charging system within the phone that will allow you to charge the battery back up to max again. As long as you take the phone off the charger when it's at that max point, you're getting the best life of the battery possible. However, if you left it on for another couple hours, it will self-discharge again.
So this is not a defect, it's by design to preserve the battery. The battery percentage reported by various apps is actually somewhat subjective. "100%" can be based on either the absolute maximum charge the battery can hold, which is what all the apps are doing. Or, you can figure the percentage based on the nominal voltage of the battery. So at the max 4.2 V could then be interpreted as close to "120%" of the nominal voltage.
If you want to verify this and have access to a voltmeter, do this: charge the battery to max using the remove/replace charging method. Now, remove the battery from the phone and take a reading; it should be around 4.18 V. Leave the battery out for a couple hours and take a reading again. You'll find that the battery is around 4.0 V. After a couple more hours, you'll find it won't vary much from that.
This is part of the reason that companies use somewhat obscure bars to indicate battery level opposed to a precise measurement. The discharge of a Li+ battery is a bit funky if you don't know about them and can cause panic and confusion if you look to closely.
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