Camera batteries and the need for a spare or spares.

[Rattus79]

You should always have a spare for days like my own wedding when I forgot to charge my only battery.

It went flat in under 10 shots.

[Analog6]

I did manage to kill the original Canon battery that came with my 300D! I use both genuine & aftermarket and have no problem with them. Whenever I get a new battery it gets a sticker on it with date of first charge. This lets me (a) rotate the batteries & (b) know when they're getting a bit long in the tooth.
With the med format digital backs genuine batteries start at$130, so I do use aftermarket - about $30 by comparison. With both the Pahse One & Leaf I found they are a bit 'loose' and can lose connection so I carry the high- tech solution - thick rubber bands - in the camera bag.
I like to have at least two betteries per body / back.

[ScottM]

I have four batteries, both Nikon and third party. Strangely, the third party ones have a higher rating than the Nikons, but it's not really noticeable. All have been going strong for three years or so.

Similar to Odille, I put a sticker on mine and record the date of charging. Although just an indication of age, it lets me rotate around the least used batteries.

Only once I've had a battery run absolutely flat out in the field, but I did have a spare with me. I've left the camera turned on and plugged into the computer overnight. That ran the battery flat; presumably as the USB controller on the camera was drawing power.

[Bennymiata]

I have a big shoot coming up soon where I will need to use 3 bodies, so I went out to Master Instruments in Marrickville (who used to be customers of mine) and bought a couple of batteries for my Canons.
Cheap too at $33.00 each, and when I got home, I put them into the Canon chargers, and they do have a chip in them as the charger and the camera recognises them just like original Canon batteries.
If you have an ABN, they will also sell to you.
I also bought some Sanyo Eneloops from them, as they are the importers, and saved around 30% on retail.

[wardiej]

I bought Sterlingtek batteries for my 30D & 40D and they are reliable as. I shoot airshows a lot and a set of Sterlingteks in my grip will run my 100-400L all day using IS and AI Servo focusing without going flat and they are 4 years old.