This is a common question concerning car batteries and normally involves car owners who plan to take a trip or a holiday for some time and leave their car behind. Though it seems to make sense, disconnecting the battery can often be the wrong decision.
First, it is important to recognize the disadvantages of disconnecting your battery terminals. Your computer system in the car needs a minimal amount of electricity to maintain the information it has stored in its memory. This information is important for the efficient operation of several different systems in your car’s engine, the transmission, and many other features. The car may in some cases even lose the ability to be started without a complete computer analysis and electronic “overhaul” should you decide to disconnect the battery for an extended period of time.
Second, what advantages do you expect to reap in disconnecting your car’s battery? Just as with the car’s onboard computer’s need for information storage, there are other systems that quietly monitor your vehicle’s current status. One in particular is a passive or active theft deterrent or alarm system that many newer cars have installed today. Without a constant source of power, this system cannot function in the way it was intended and may give a criminal the opportunity to break in and steal your car’s stereo or other valuable equipment. The loss could exceed any perceived loss of battery life during this period of time.
Finally, your car battery has plenty of stored charge and is designed for long periods of disuse. Most new car batteries can last for several weeks without the car being started and still have plenty of electricity available to start the car when you return. However, if the thought of leaving your car’s battery connected still bothers you, there are maintenance chargers available that can be left connected to the battery for long periods of time. This will require an electrical outlet, such as in a garage or shop, since it would not be wise to use such equipment outdoors where wild animals or the environment could cause damage to the charger.
The best advice that can be given is to keep your car’s battery connected to your car. The advantages to keeping the battery connected will normally far outweigh any disadvantages and will most likely ensure that your car will be able to start once you have returned from your holiday.