Due to the way batteries discharge it's important that you test the battery after it's been sitting for at least. Testing a battery with a multimeter is a simple process.
If you're having problems starting your car, you might have a battery issue. See here for basic instructions on testing a car battery with a multimeter.
If you don't have a multimeter to tell you the voltage of your battery, you can do a test of your electrical system by starting the car and turning on the headlights.
Few things can ruin an adventurous road trip as quickly as a dead battery in a small town in the middle of nowhere — and with no mechanic. A car's battery is .