A car's battery is supposed to maintain its power once the engine (and hence the electrical components of the car) is switched off. Sometimes, however, this doesn't happen, and current drain continues with the car switch off. This problem may be caused by different things such as:

Electrical Devices Running With the Engine Off

Just because the engine is off, it doesn't mean that its electrical systems are off too. Things like navigational systems, running radios and plugged in devices (such as smartphones) may continue draining off your battery even with the engine off. One device may not cause a noticeable problem. However, the more devices you have plugged in, the faster your battery is likely to be drained.

Short Circuit

A short-circuit may also drain your battery even with the engine off. How do you confirm that this is what is happening? Well, a simple test you can do at home involves switching off the engine, popping up the hood, and disabling the illumination light under the hood. Next, disconnect the negative battery terminal and connect a test light to it. A brightly illuminated test light signifies a short circuit; a dim light means the electrical systems aren't the problem.

Alternatively, you can disconnect the negative terminal and use a multimeter to bridge the ensuing gap. The DC amps reading should be very minimal, almost nonexistent. If you get a reasonable reading, then something else is draining the battery.

Key-Off Drain

New cars come with numerous computers or electronic chips that operate sensors, anti-collision systems, cruise controls and other smart car functions. These electronic modules are supposed to switch off when you turn off the engine. Some of them, such as navigational systems, are not supposed to lose their memory, so they have integrated Keep Alive Memory (KAM) systems to preserve some memory.

Unfortunately, a malfunction may occur, and the chips may continue to run at full power even with the engine off. Depending on how computerized your car is, this current drain may be enormous. This is not a diagnosis you should try at home, but rather leave it to professional mechanics like those at Southside Auto Repair.

These are just a few examples of what may be draining your battery when the engine is off. It might also be that your battery is just old, or there may be other hidden problems. Therefore, if your relatively new battery is losing power with the engine off, and you have turned off or unplugged other power-hungry objects, then consult your mechanic for further diagnosis.