Has anyone tried any 3rd party replacements for lithium ion camera batteries? I would like couple spares for my nikon en-el1 pack, and I see various taiwanese made replacements available on the internet for a fraction of the price. These invariably advertise a higher capacity than my nikon original battery (680mAh). Can the replacements be trusted? If they last for as many shots as the original and can be charged even half as many times, it's a deal.