I also bought a separte batterry charger which did charge the battery -- verified with VOM. When installing the batterry in my N810 it didn't work. This problem was solved by bending a piece of business card stock and using it for a shim to press the battery against the N810's contacts. A fully charged Mugen battery reports the same 10 day and 7 hour estimate as the Nokia battery but it seems to stay at that level longer than the Nokia battery. I would buy a Mugen again since it is less expensive. Personaly I'd avoid the bargin batteries on ebay.