You might be moving away and leaving your car idle for a time. Perhaps you’re going on a backpacking trip around Europe for the next three months or perhaps you’ve found your grandad’s old 1975 Holden Gemini in the shed that’s been sitting there gathering dust for the past five years.
There are many reasons a car sits idle for long periods of time and this will have an impact on the battery and how much charge it has and can keep.
What happens to a car battery when it sits idle for a long period of time?
Like any tool or piece of machinery/equipment in our lives, they’re made to be used. You might have heard the saying ‘A ship in harbour is safe, but that is not what ships are built for’ and the same can be true of cars and their batteries. Batteries were made to be used and if they’re not used for extended periods of time, this will have an impact on them.
Unless you disconnect your battery your car is going to draw a charge from it. Whilst there are many electronics in your car that are powered by the alternator whilst the car is on, there are also items that will always be taking a small amount of charge from your car regardless of if the car is on or not.
This is called parasitic draw or parasitic drain.
There are several items in a modern car that will cause a normal amount of parasitic draw including:-
- The clock
- The alarm system
- The radio
These shouldn’t have any major impacts on a car that’s driven regularly however, if the car is sitting idle for extended periods of time, these items, even though they only draw a very small amount of power from the battery, will eventually drain the battery entirely if left long enough.
How long does it take for a car battery to die?
This really depends on several factors. Leaving your lights on overnight for example can kill your battery entirely whereas a car that only has an interior light left on might take a couple of days to drain.
Several factors will impact on the length of time it takes for a battery to drain from ‘normal’ parasitic drain including the age of the car, the age of the battery, the weather conditions it’s being stored in and the type of vehicle.
As a general rule of thumb, if you’re leaving your car sitting for extended periods of time, it can take anywhere from a few weeks to a couple of months for your battery to die. Any longer than a couple of months and you’re really playing with fire.
How can I make sure my car battery doesn’t die if I’m not using my car?
One of the easiest ways to make sure your battery doesn’t die if you’re not using your car is to take it for a drive. If you can’t do it because you’re away, have someone else take it out once a week or at least once a fortnight. This will help maintain your battery and keep it in working condition.
If you’re not able to drive or have someone drive the vehicle, take the battery out so things like the alarm system and clock aren’t drawing power from it whilst you’re away.
Note: Please be aware that some models of vehicles have an anti-theft feature that will require you to add a special code if the car is disconnected from the battery. If you don’t know what this code is (if the previous owner doesn’t provide it on a second hand car for example) you may be charged a fee by the car maker to reset the code.