15. HOW LONG CAN I PARK MY CAR?
The amount of time, usually referred to as "airport or garage time," that you can leave your car parked and still start your engine is based on such things as the state-of-charge of the battery, the Reserve Capacity, the amount of natural self discharge and parasitic load, and temperature. Car manufacturers normally design for at least 14 days or more airport time; they assume a fully charged battery in good condition, moderate weather, and no additions to the original car's parasitic load (for example, an aftermarket alarm system). When a battery drops to 80% state-of-charge or less, sulfation starts occurring, and this will reduce the capacity of the battery.
If you leave your car parked for more than two weeks, then you have several options:
15.1. The best option is to connect an automatic electric or solar float "trickle" charger to your car battery. You will need 13.8 VDC and at least 0.5 amps to overcome the natural self-discharge and parasitic load.
15.2. Install a battery with a larger reserve capacity.
15.3. Jump the battery and hope that there is no latent damage.
15.4. Connect a large, deep cycle battery in parallel.
15.5. Disconnect the negative terminal, but be sure that you have saved any security codes or radio stations that will have to be reprogrammed.
15.6. Plan to replace the battery if it fails to retain a charge, especially if it is over three years old or sealed, and you live in a hot climate.
15.7. Have someone drive your car during the day on the highway every two weeks 10 to 15 minutes to recharge the battery.