Of all things to go wrong with your car, a bad battery is one of the most common. You had better get used to understanding how the hookups work, because there will be times when you need to disconnect and reconnect them.
Dirty or corroded terminals can prevent proper electrical contact, keeping the engine from starting; the initial jolt of electricity needed to turn the motor over is important most days, but becomes vital in life-threatening situations (e.g. stranded in a hot desert or in the middle of nowhere in winter).
Remember, turning wheels are not the only thing that stop when the battery goes out; none of your vehicle’s systems will engage if this device is out, save perhaps for the interior lights, but these too will eventually die out when the battery loses its charge. In most cases, a faulty battery is due simply to age. Most models, even the high capacity ones (the higher the cranking amps, the stronger the startup charge); tend to last no longer than three years. It is generally advised to replace them around this time to be on the safe side, though yours may live well beyond that point.
When the battery is to blame: signs to look for
A quick and easy diagnosis starts with the ignition. If after turning the key, the motor continues to crank but not fire, you can bet a bad battery is the reason. Without the proper voltage, there simply will not be enough juice to get the engine running. Thankfully, your car’s built in charging system (i.e. the alternator) will keep the battery operational for a couple of days, long enough to install a replacement. Be careful though, because if the vehicle is left sitting for an extended period, it will not start without jumper cables.
The opposite of inadequate charge is no charge at all. In these situations, the battery lacks the energy to power not just the motor, but also its electrical system. The engine will not crank and the instrument panel will not light up. Corroded terminals may also cause the battery to jump back and forth between fine and problematic, so check these first.