if you shoot weddings with a battery pack..

I am cureous how many times you change the battery, and how many shots you average per wedding. I know this is a wide open question, but I had to ask.

It will vary with any camera. I use 2 5D MKII's for weddings, I don't use grips, and I never have to change the battery during weddings. I can easily get over 1,000 frames per body/battery.

wow that is alot.

Camera or flash?

With 40D, 7D, and D700, two batteries lasts me more than a wedding. The D700 is pretty mental, I could probably shoot two or three weddings on two batteries, each camera doing 700-1000 shots.

With 580EX II or SB900 I use 8 cell battery packs, as well as batteries in the flash. I practically never have to change cells at a wedding.

Nice... I have a 550ex, yes I will be using it. I bought a power pack and a battery pack, I now will own 5 batteries for the 60D. I guess I got a little crazy on the 60D batteries, but you can never be to prepared!

When I shot Canon I had heaps of the BP511 batteries, they're only $12 or so each. The Nikon ones are only a bit more expensive, but I only have six for two cameras, ie two spares, but I doubt i'll ever need the spares. I keep them all charged anyway.

PixelHK battery packs for the flashes work well, and are quite cheap.

I rarely change batteries on any of my bodies at a wedding. On the 5D MKII's I'll normally get well over 1000 frames before I think about changing. As I normally shoot around 500-700 per 5D MKII it is never an issue. My 60D is much the same I only took about 300 on it at the last wedding but it has no problem with doing a similar amount the the 5D MKII.

I did set up on camera to capture a timelapse of the reception on Saturday. One of the 5D MKII's took 2780 pictures over a three hour period before the battery ran out.

I take 8 camera batteries with me for 4 bodies. To be honest 2 spare would easily be enough but I prefer to be over cautious.

yeah, i have had similar experiences as those above.
A gripped body will last me all day, even using IS for most of the day.
i find IS uses too much battery for me to rely on a single battery all day.

i use a battery pack on my ocf, and never change the batteries/pack during a wedding day.

i bring a lot of extra batteries too, and never really have to replace batteries in the bodies.
On camera flash batteries I replace throughout the day.

But i think my bp-511 battery charger is not functioning properly as this last weekend's wedding, my wife's 50D died early in the reception.
Both batteries (gripped) dead.
That's never happened before, but thank god we had backup batteries.
The backup batteries barely made it through the reception!

Battery usage will also vary on camera settings like display, camera flash usage if its equipped with it and you use it, lens with IS, etc. those are minor but it all adds up.

I can do back to back (i.e. Saturday & Sunday) wedding on a pair of batteries in a grip and still have plenty of life left!

Depends on whether I am photo only or video. For photo only, I usually can get by with 1 battery. Video eats through batteries like crazy, so I end up charging batteries on-site while I am shooting, etc. Don't have grips for my cameras.

For flash, I use battery packs for my 580EXII's, mainly for faster recycle times. They usually last the entire day.

i know your asking about weddings - But just to show you an example of battery life - i set my camera up to shot a time lapse tethered to a laptop (so i had 500 GB of memory), i used my t1i with grib and 2 after market batterys, i took 4732 shots before my battery went dead -

I have two batteries for my 60D, and have never needed the second one - though I don't shoot weddings. I usually alternate batteries, just out of principle and so both get used approximately evenly - but the lowest I've ever gotten was one remaining bar at the end of a five-hour portrait session (eight different people).

I'll probably wind up getting a grip sooner or later anyway, not for extended batty life, but simply for better ergonomics and control when shooting in portrait orientation.

I was actually just considering getting a battery pack for my flash - something Im going to start to look into.

If we are talking for cameras, using my grip I usually dont get below 50-60% on each camera after a wedding.