I tried out the knockoff battery that came with that Ebay charger and it registers for 3 hours of use compared to Nokia's 7 hour run time. I don't know about actually damaging the N810 because when it's running, other than the reduced battery life, there's very little to show that it is affecting the Nokia N810 in a negative way. For 10 US dollars ( battery and charger ) I wasn't expecting much from the battery, but the charger works fine with the normal retail Nokia batteries.