Don't keep them in a pocket where they can get humid - either from your body sweat, or from rain. I tested the battery - started off fine, cheap and around 1700mAh - but they dropped fast (to less than 1000mAh), and went dead in my pocket while skiing.

I have this "blue battery" as best: http://www.aliexpress.com/item/2600m...601760234.html

Maybe it can deliver 2000mAh - I doubt what they claim, and the factory that first produced them does not produce any more, but these look the same and they claim it is an improvement. I have tested batteries at 4000mAh - but these are bigger, made for Samsung. The size determines the capacity. The N900 is the only phone around where you can reset the charge, none of the Android apps work.