I have a Canon 50d that I am taking on a camping trip in several weeks. I was wondering if it is possible to charge the battery from a car's auxiliary power outlet. What would I need to do this, if it is indeed possible?
You can buy dedicated accessories for charging all kinds of stuff, or you can spend a little more and get a car converter 12V -> 110V, or 220V, depending on what your chargers need.
Then you can connect just about any standard device to it, as long as its current (wattage) requirements are not too high.
Here is one similar to one I have and it came in handy many times - most notably when camping:
If you want an official Canon accessory, you can use the CB-570 Car Battery Cable. It works with the CG-570 Battery Charger and is listed on the accessories page for the 50d.
As others mentioned, a power inverter is also a more general solution, though converting from DC to AC back to DC will use additional power and put additional strain on your alternator. It's not a big deal, but it is worth noting since it will have a larger impact on millage (though still likely insignificant overall.)
It becomes a question of if you want a direct and efficient solution or a more generally useful device that can be used for multiple needs.
Yes it is possible. Buy a camera charger with car adapter with it. it's around $10 at Amazon.
SOME LiIon stand alone chargers have 12 VDC input. Some have a car cord only (supplied). Others use a mains to 12v power pack to operate them. These can be operated from 12 VDC from a car by inputting it at the 12V input.
A number here on ebay from about $US5.
12V with auto cigarette lighter plug and cord ebay $5.43. NJ source allegedly.
About $US13. Posts from Hong Kong. MAY have mains and car inputs. Read ad carefully, as ever ebay Battery charger for Canon BP-511 EOS 50D 40D 30D 60 G6