Car Battery, New & Used:
It is imperative that your vehicle has a working battery. No battery, no running vehicle. Batteries will often last three to five years. If the battery is older than that, it is a good suggestion to replace it even though it might not appear there are any symptoms with it yet. If your vehicle doesn't start, one of the things is to check the age of the battery and make sure it is not loose or the battery cables aren't loose either.
If the engine turns over but it will still not start, it could be the battery. Is there any life in your vehicle at all, or does everything seem to be dead? One day your car could have issue starting and the next it could start fine. This could be a sign that your battery is dying. There is always the chance it could be something more like a starter, but it is a good idea to check out the battery first.
Always have a set of jumper cables handy to get your vehicle running again. Remember that if you have to jump start your battery on multiple occasions, it is probably time to replace your battery before it will not ever start again.