It is not recommended that a car is left running for an extended period of time for the purpose of charging the battery, as it can cause unnecessary wear and tear on the engine and waste fuel. In most cases, it is sufficient to run the engine for 10-15 minutes to help charge the battery, however this may not be enough to fully recharge the battery. It is generally much more effective to charge the battery using a battery charger and leaving it to charge for 8-10 hours.
