Parking for a Long Trip: How to Keep Your Battery Alive While You Are Away

A car sitting unused loses charge slowly, even when it is off. Modern cars draw a small amount of power for the alarm, computers and keyless entry. A healthy battery may last weeks. A weak one may not last a week.

Before you leave

• Have an older battery tested. If it is past four years old, it is the one most likely to fail while you are away.
• Take a good drive of 30 minutes or more just before parking so the battery starts full.
• Turn off everything: lights, interior lights, chargers and any accessories plugged into the car.
• Make sure all doors, the trunk and the glovebox light are fully closed.

If you will be gone a long time

• Use a smart battery maintainer if you have power in your garage. It keeps the battery topped up without overcharging.
• Ask someone to drive the car for 20 to 30 minutes every week or two. Idling in the driveway for a few minutes does not do much.
• Avoid disconnecting the battery on a modern car unless you know what you are doing, since you may lose settings and need to relearn some systems.

Back from a trip to a dead battery

It happens even when you plan ahead, especially after a month at the airport or on a ferry trip. A mobile technician can come to where the car is parked, test the battery and replace it if needed, so you do not have to arrange a tow.