To Disconnect or Not to Disconnect your Car Battery?

Written by admin on October 24th, 2011

There are many schools of thought regarding the best way to avoid a dead or flat battery upon returning from an extended holiday. Some experts recommend disconnecting the battery, while others insist a trip of less than 30 days requires no such measures. In short, whether to disconnect or not depends on the age of the car, the age and condition of the battery, the length of time the car will remain idle, where it will be stored, and the expected temperature.

Older cars have fewer electronic or computerized systems that create a passive drain on the battery. Newer cars rely heavily on the battery for alarms, air suspension, and similar on-going systems that draw power, even when the car is off. In some newer cars, disconnecting the battery can result in the computer resetting to factory defaults, necessitating a trip to the dealership before certain systems will work again. For older cars with less dependence on passive systems and computers, disconnecting the battery is fine, although not always necessary. For newer cars, a quick call to the dealership can provide information about specific models and the effects of disconnecting the battery.

Battery age, overall condition, and charge level are also of concern. A good battery should be able to maintain a charge for up to a month without requiring a jump start. For extended holidays lasting more than a couple of weeks, consider putting the battery on a charger overnight to ensure the charge level is at peak capacity before leaving. Batteries with corroded terminals or batteries more than a year old may not last as long before discharging themselves. If the car has a new battery in good condition and the holiday is expected to last less than a month, no extra steps should be necessary beyond securing the car.

Location and temperature can, however, influence the expected life of an idle battery. Storing a car outdoors during the winter months in a cold climate, for example, will shorten the expected life of an idle battery. Indoor storage during warmer months, or during cold months in moderate climates, provides the best chance of the battery maintaining a charge without needing to disconnect it.

When in doubt as to the best option for preparing a car for an extended period of idleness, consider a smart charger or battery manager, rather than disconnecting the battery. These mechanisms differ from a trickle charger in that the slow charge introduced to the battery is not continuous. Trickle chargers are not recommended, as they can overcharge the battery and kill it. Instead, a smart charger or battery manager has an electronic chip that senses the charge level of the battery, turning on or off as needed automatically. These devices plug into a wall outlet, although solar-powered versions are available for cars stored without access to an AC outlet.

The most important factor in choosing how to maintain car batteries whilst on holiday is not to rely on jump starting a dead battery upon return. Most cars have sensitive electronic or computer equipment that can suffer damage from the sudden influx of current created by jump starting. While this is not necessarily a problem for older cars, allowing a battery to go dead seriously shortens its lifespan. There is no guarantee the battery will hold a charge once it goes dead.

For most ordinary cars we recommend CTEK Battery Chargers either the CTEK XS4003 or the CTEK XS7000 whilst we do stock a range of Optimiate battery chargers. For commercial vehicles we’d suggest either the CTEK XS25000, CTEK XT4000 or the CTEK XT14000.

Image © Andy Armstrong

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