I just received a cheapo Chinese 3800 mAh battery from eBay ($9.99 and free shipping, I had $6.24 in expiring eBay bucks, so I figured why not?)
Charged it up last night, with my phone off, after resetting the battery stats in CWM. I let it go about 2 hours past fully charging. Then started using it. First charge is not so good, going to let it go as low on battery as I can before plugging it back in. Will see if it does any better. I'll add battery life screen shots at 10% and again at 5% for this charge cycle and the next, then I'll post another set next week, so everyone can see if it improves any.
I have contacted the seller, as the neck cover they shipped (shiny, slick, black plastic) does not snap in on the top right hand side...
Also I noticed while swapping the two batteries, the 3800 is only 3.7v the stock is 3.8v...