Much can be a battery apart from the capacity not say, but here is one for the Nikon D3100 and with this camera the manufacturer wants to prohibit the use of alternative batteries through the firmware, so you need to purchase the expensive original batteries. This charger does not cost just a third of the price of the original, but can actually be used in the Nikon. This makes it worth the price, even if the capacity should be slightly lower. Since the performance of the original battery is very good and this is in any case intended only as an emergency reserve, it makes but for me not so much, if the capacity should be actually lower.
But only for compatibility at this price I give five stars.
