Why do car batteries go flat when sitting? 

If your car battery has gone flat or is continuously going flat, you know how inconvenient it can be when you need to use your car. It may come as a surprise, but a flat battery can be caused by more than the obvious reasons, such as leaving your lights on (see more reasons for flat car batteries here). Unfortunately, your car simply just sitting without use can result in a flat battery. 

Car charging system.

This is because the battery still discharges while it is sitting still. Though it is slower than when the car is running, if the car is sitting long enough, the battery will run down over time. There are many different reasons the battery might drain when it is not in use. For example, your car may have a parasitic battery drain. This is when the battery continuously discharges after your car has been turned off. Depending on the car, there are some possible electrical devices that may be technically on even though the car is off, such as a security system or the radio. If this is occurring in your car, the battery could go flat overnight, or when the car is left without starting for a few days or weeks.

How long does your car have to sit before it goes flat? 

The amount of time it takes for a car battery to go flat depends on the car as the charging systems of different cars vary (more on charging systems here). One factor is the age of the car. Modern vehicles can store energy for longer than older ones, so it may take weeks for the battery to go flat. 

Another factor is the type of battery your car has. For example, Premium batteries are made with additional measures that increase their life, which increases the amount of time the battery can sit without use. 

Finally, the electrical systems in the car can impact the battery’s life. As mentioned cars with additional systems, such as security systems, may be draining the battery more than cars without an alarm/security system.  European-made cars seem particularly vulnerable to battery drain if left to sit for more than a few days. 


What factors can cause extra strain on the battery? 

There are circumstances that can make the car more prone to a drained battery when sitting. Some of these include: 

Switches left on: Obviously leaving things like lights and heat on can drain the battery, but also, leaving things plugged into USB ports for example can as well.

Old battery: If your car battery is old, you may experience a continuously drained battery. If you have noticed this or bought a used car, it is worth getting your car battery looked at and possibly buying a new battery. 

Faults in other parts of the battery system: Other battery-related parts such as the alternator or starting system may be resulting in an over or under-charged battery which may make your car battery go flat while sitting.

Weather: When the temperature gets lower, it is important to keep your car in the garage if possible. Colder temperatures are harder on car batteries and cause the battery to go flat more quickly. 

Flat battery fix in Hamilton

Has your car battery gone flat after sitting? If so, we can help! 

When you book an appointment with Grimmer Motors, our friendly, helpful mechanics can quickly and easily diagnose the cause of a car battery that isn’t holding its charge or is being drained. Whether it’s faulty wiring, an old battery in need of replacement, or incorrect installation of an accessory, our team can provide a solution you can count on.

For car battery diagnostics, servicing, and replacement in Hamilton, contact Grimmer Motors today!


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