Why does my car battery discharge when the car is parked?

If your car battery discharges while the car is parked, there may be several reasons.

All modern cars consume some current even when switched off. This is needed for functions such as alarms, central locking and various electronic systems.

However, if current consumption becomes too high, the battery may discharge.

Common causes include:

• Worn battery: The battery has lost capacity and can no longer hold its charge properly.

• Short journeys: The battery does not have time to recover the energy used to start the engine.

• Additional equipment: Dashcams, GPS trackers or aftermarket electronics, for example, may draw current when the car is switched off.

• Electrical faults: A component may continue drawing current even when the car is switched off.

• Charging problems: The alternator or car’s charging system may not be charging the battery correctly.

• Long-term parking: Even normal standby current can discharge a battery if the car remains unused for long enough.

How do I find the problem?

Start by checking the battery’s condition and charge level.

If the battery is healthy but still discharges, the car’s standby current may need to be checked.

Please note that modern cars may take a while to enter sleep mode. A current measurement taken immediately after switching off the car may therefore give misleading results.

If the problem started after installing new equipment, pay particular attention to how it is connected and whether it switches off correctly.

A battery charger with maintenance charging can be a good option for vehicles that are rarely used, but it will not fix an underlying electrical fault.