You can do one of 3 things and it will work.

1) buy an INVERTER, which a device that takes 12 volt DC car battery power and
converts it to 110 volt AC (wall power). Inverters come in all kinds of sizes
depending on your needs. Small 100 watt inverters cost about $40-50. An inverter will use more power than the next alternative.

2) Buy a 12 volt to 7.2 volt Canon battery adapter. You can either charge
a battery directly from your cigarette lighter (or other 12volt source),
or run the camera itself.

3) Go to http://www.hayesequipment.com and buy a honda generator.
They sell all kinds and sizes of generators, but the one I bought,
the honda EU2000i can output a constant 1600 watts or 2000 surge watts.
That's enough to run not only the battery charger, but three 500 watt lights.
Honda makes a 1000 watt model as does Yamaha.

When the blackout hit us here, we used our lovely honda to power the
fridge for some 15 minute intervals, then also used it to power up my
whole NLE rig (NOT at the same time as the fridge!!!). Worked great!