How does cold weather affect your car battery?

When you turn the ignition key to start your car, everything depends on the battery hidden somewhere in your car's engine compartment. Car batteries usually don't have to work very hard in warm weather, but when wintery conditions arrive, the engine is harder to turn over, so the battery has to work harder.

Last year, NRMA roadside assistance and our battery technicians responded to over 400,000 calls for flat batteries, so we're here if you need us. There are, however, some things you can do to prevent issues and extend your battery's life.

Temperature plays an important role in the performance of your battery

Most batteries in new cars should last three years on average and a cold snap will sort out the good from the bad!

Inside the typical lead acid battery are lead plates in electrolyte liquid which creates an electro-chemical reaction to produce a charge to the battery terminals. Heat accelerates this chemical activity but also speeds up the internal corrosion with the cells which in turn reduces the lifespan of your battery.

This is particularly true of batteries that repeatedly reach high internal temperatures, and once capacity has been damaged by heat, it can’t be restored. But just as heat speeds up chemical reactions, cold temperatures slow them down. That’s why you might feel your battery can become sluggish in winter, even though its state of charge may remain unchanged.

At colder temperatures, the battery’s ability to provide sufficient power to start and run a vehicle is diminished. Automotive batteries are rated in CCA (Cold-Cranking Amperage). This is the amount of current a battery can deliver for 30 seconds at -18 C without dropping to a specified cut-off voltage. A fully charged lead-acid battery can survive up to –50 C, but a battery with a low state of charge can freeze at –1 C. When the water in a battery freezes it expands and can cause irreparable damage to the cells.

Learn how to maintain your car battery

We recommend that car owners start paying close attention to their batteries after three years of installation. If your battery is starting to go, the first thing you'll probably notice is that the car sounds sluggish when trying to start. This is a major warning sign that shouldn't be ignored.

If you hear sluggish sounds when you start up your car, do not immediately assume that the battery needs replacing. Check that the battery connections are tight and that the wires are not broken or disconnected. Also ensure that your terminals are clean - you can get them cleaned regularly during every major service so ask your mechanic. 

If your battery has caps, remove them and check that the fluid inside is about 5mm above the plates, or between the levels as indicated on the battery case. If low, top up with deionised water and avoid overfilling. Mop up any spillage. Some batteries are permanently sealed and do not require maintenance, so you won't be able to check the fluid if this is the case.

If you are in any doubt, contact the team at NRMA Batteries and we can help.