There was a time, a camera, even professional ones, needed no batteries at all. In fact, you could buy a new one until as recently as 2006.
I have such a habit of purchasing a spare battery for any camera that might become my primary that I once purchased an EN-EL4a for my Nikon D3.
Normally I only buy the manufacturers approved batteries, because there are a lot of stories floating on the internet about exploding Li-Ion batteries, and because ever since Sony introduced the infoLithium, many manufacturers introduce an extra “smart” feature with circuitry where the lithium battery informs the camera about its age and charge, and I figure why risk it?
Nowadays, 3rd parties have done a good job of figuring it out, so I decided to take a dip.
Another reason for this purchase is the Olympus PS-BLS-1 holds 1080 mAH of charge, while this replacement is rated at 1800 mAH—almost twice as much!
Continue reading about the what, where and why of spare camera batteries after the jump