CAR & DEEP CYCLE BATTERIES
Last Updated on March 12, 2003
Written and compiled By Bill Darden (freely reproducible public domain)
Re-produced here by www.optimabattery.co.uk for your information, and it will be updated regularly.
The amount of time, usually referred to as "airport or garage time", that you can leave your vehicle parked and still start your engine is based on such things as the battery's State-of-Charge, 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 after market alarm system). When a battery drops below 100% State-of-Charge, sulfation starts occurring, and this can also reduce the capacity of the battery.
If you leave your vehicle parked for more than two weeks, then you have several options:
15.1. The best option is to connect an voltage regulated float charger or solar float charger to your car battery. You will need 13.2 VDC and at least .5 amps (500 milliamps) 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 battery in parallel.
15.5. Disconnect the negative battery cable, but be sure that you have saved any security codes or radio stations presets that will have to be reprogrammed.
15.6. Replace the battery, 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 for at least 15 minutes to recharge the battery.