[Droid Eris Accessories] pkopalek:
The 3500mah batteries will fit the Eris, Hero, Evo, and Incredible, BUT they do come with custom backs from Seidio. So I got the 3500 one for the Eris, and it does have a cheeseburger-sized casing on it to replace the normal back. No, the camera backing does NOT have an extra back cover, but the internal glass cover inside it is just fine. I find no protection issues with it, and it takes better pictures, because the indented shape of the back cover shades the camera from more ambient light.

The 1750mAh batteries will ALSO fit the Eris, Hero, Evo, and Incredible, but they do NOT need a custom back. They fit in the stock casing.

The stock is 1300mah. The rating of '1750' for those seidios does seem reasonably reliable, about 1/3 more juice.

The 3500's are just MONSTER trucks. They last forever. I have failed to kill the battery in a single day. Honestly. It's something like 2 and 2/3 times the stock Eris battery, in terms of capacity. I have now given this battery to my gf who has Cricket, and due to having a Slot Cycle Index of 0, and poorer reception than Verizon, and doing tons of texting, she CHEWS through batteries. But not the 3500.

The 1750, she still has to charge mid-day. The 3500 - done deal.

The phone has to calibrate to your 3500 a little bit differently than your other batteries. Wiping battery stats in Recovery is a good idea. But truthfully, not completely necessary. The battery % just reads voltage, and kind of 'guesses' based on how much the phone was just being used, and whether it's in a charging state or not.

If your battery is draining REAL fast, with the 3500, try putting your stock battery in there and see how fast it's dying. I bet it's dying WAY faster, if your 3500's not defective. Put your phone in airplane mode overnight, and see how much % you lose. Shouldn't be too much. If you're fully charged, it might still say 'fully charged' when you wake up.

If it does, then you probably have some process syncing/talking to the internet constantly.

Check accounts and sync > look through each of them (facebook, twitter, flickr, google, etc) and make sure none of them have an ERROR.

For example, I had a battery drain problem REAL bad. After a long time, I noticed that, in accounts and sync > pkopalek@gmail, my 'Contacts' for pkopalek@gmail.com were FAILING to sync for some reason. No worries. I unchecked the box for it. And a week or so later, I checked the box back the way it was, and life was OK.

The two things that murder battery the most are screen brightness/being on, and apps talking to the Internet.

If you have wifi at home, turn it on. It uses roughly 1/5 of the battery life that 3g uses (if you have full reception on both, and it's even a SMALLER fraction if you have weak 3g reception in your area).

'Partial-Wake usage' is blamed for a lot of battery loss - but usually it's because whatever apps are DOING the partial-wake usage (or wakelock as they call it sometimes) are talking to the INTERNET excessively (like email syncing every 5 minutes, or Facebook set to refresh every 15 minutes, or whatever). The fact that they're keeping your phone awake only really allows your processor to clock up, instead of to 480mhz, up to 528 or 768 (or whatever your max is - or whatever you have set in SetCPU or whatever app you use). 528mhz uses a higher voltage than 480mhz (a higher 'step', so 245mhz and 480mhz use the same voltage, and 528mhz+ uses a higher voltage)