Is a back up battery necessary?

Sportidi wrote in post #10790826
I can't see myself going on a full on 4 hour photo session. 2 hours maybe.....

I recently shot 22 concerts in 3 days. Only 2 hrs... I wish

It really depends on what you're shooting, where you're shooting it, and how cold it is where you're shooting.

I have 4 batteries for my 5D and 50D (they take the same battery). For a while I tried to get by with just 3 batteries, but there were times when I'd be out on location and use them all up. It'd suck to have to sit in my car, waiting for a spare to recharge. So I bought the 4th, and so far the 4 have been sufficient.

Keep in mind that I photograph wildlife, and it is often below freezing where/when I shoot. Also, I believe that using the big supertelephotos use up battery life quickly, as the AF has to move big, heavy glass elements back and forth.

For "normal" shooting such as weddings and such, I cannot imagine that you'd need a spare battery for a 7D - even if you shoot 2,000 to 3,000 frames in a day.

I use a Canon 1D Mark 1 and the battery life is pretty short so I carry 2 extras.

Always have a backup. That and always have an escape plan

Tom Reichner wrote in post #10813403
It really depends on what you're shooting, where you're shooting it, and how cold it is where you're shooting.

For "normal" shooting such as weddings and such, I cannot imagine that you'd need a spare battery for a 7D - even if you shoot 2,000 to 3,000 frames in a day.

OP here....Tom I think you've answered my question.

We're going to Bora Bora in October, and the temperatures will be tropical.

I cant see myself taking more than 500 frames a day, and no more than 20 shots at night.

So technically speaking, if I recharge the original battery each night I should be safe.

If you think I'm wrong please let me know....

I've got a 7D with a grip + a 5DMkII with 5 batteries total.
Normally it's power to spare...
but the timing of use, health troubles, just plain laziness and/or whatever other reasons that cause one to forget to double check the state of charge before a shoot..
So yes, even with 5 batteries, there's still been a instance where I ran out of power!!!!!

I would have been SOL, if I hadn't brought my big power pack/invertor with me!!!
(((LOL! AHHHH thank you BoyScouts ... that "Be prepared" helps.)))
It allowed me to recharge the batteries as well as keep shooting with the one cam using the AC adapter.

I keep one canon battery as a spare. I used to have a OEM battery from adorama and it ran out quickly. You never know when you may need it.