Most consumers don't realize they can get a dual 5D battery charger for half the price of a regular 5D Canon battery charger.
A lot of people pay about $70 for a charger that only charges one battery at a time. If you know where to look (this website) you can just as easily pay only about $35 for a piece that charges two batteries at once.
If you don't already realize the advantage of a charging two batteries at once on the same charger allow me to explain why this is such a great thing.
If you're shooting at night and are going to be shooting the next morning (or even just the next day) you'll want to charge all of your batteries before the next day's shoot. With a single 5D battery charger what often happens is that you'll set the charger and then after a few hours you'll need to replace the battery that's now fully charged with a second battery that was drained during the evening shoot. Unfortunately, this exchange often has to happen in the middle of the night - an issue that clearly disrupts sleep and can make for a frustrating experience when you have to get up early to shoot the next day.
With a dual battery charger all you have to do at the end of the day is set both empty batteries in the charger, plug it in (just like a cell phone charger), and forget about it until the morning. If you have have batteries to charge to ensure that there's no way you'll run out of power on a long day of shooting simply pick up two dual Canon 5D dual battery chargers. You'll still only be spending around the same amount of money as if you bought a single charger.
Here's how the breakdown works out if you've found the best prices (which is what I've found for you here):
A single 5D battery charger (like the one below) on amazon.com typically costs between $50 - $75. You can search that selection here.

Alternatively, a dual battery charger like the one below can be found for only $35 with this company.

I only found out about this great deal after many nights of disturbed sleep while trying to charge batteries over night when coming off of a night shoot with a day shoot starting the next morning. Someone else in my office actually found this great deal after several people in our office spend days trying to find a good deal on a double 5D battery charger.
I was perplexed at how difficult it was for me to find this great deal on a dual 5D battery charger for Canon cameras. It took me a few months to get around to putting up this website but I'm hoping that this site finally serves as a simple place to find the best deals on these chargers.
On a final note if running out of power is a major concern you should consider getting an AC car adapter so you can charge batteries in your car. To check out prices of compact flash card readers, 5D cameras, camera backpacks, compact flash cards, 7D EOS cameras, Canon batteries, compact flash card cases, Canon lens caps, 5D camera lenses, and other 5D accessories take a look at those sections of this website.
On a final note if running out of power is a major concern you should consider getting an AC car adapter so you can charge batteries in your car. To check out prices of compact flash card readers, 5D cameras, camera backpacks, compact flash cards, 7D EOS cameras, Canon batteries, compact flash card cases, Canon lens caps, 5D camera lenses, and other 5D accessories take a look at those sections of this website.