Summer's Heat Makes Your Car Battery Worse In Winter. Here's Why

Evaporation and chemical corrosion can lead to less available power for cold starts.

Andy Stonehouse | 

Apr 21, 2023 | 3 min read

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Just like a day in the scorching sun will leave you thirsty and feeling drained, a summer of blazing heat can impact the life and capability of your car’s 12-volt battery, making it less capable of providing the power for a start when it’s cold.

Heat Can Be Just As Bad As Cold Weather For Your Battery

Modern lead-acid batteries still rely on chemical reactions to provide the power for your car’s ever-increasing range of electronic systems and accessories. Extended exposure to high outdoor temperatures leads to the evaporation of the fluids inside your battery, which can result in a weakened charge.

High temperatures can also amplify corrosion, damaging the internal components of your battery, and leading to less power and a much shorter life. The net result is damage and a decrease in available power, which itself will be amplified by the winter’s cold — another force which slows the chemical reactions that give cars starting and operating power.

How Do I Test My Battery’s Health

Unlike the early days of motoring, which required owners or mechanics to routinely top off the fluids in their batteries to cope with seasonal temperature changes, many batteries today are of the sealed, non-maintenance variety. They only last an average of three to five years.

You may still be able to see the fluid levels in small maintenance windows or water level indicators in some modern batteries. In those cases, distilled or deionized water can be added to help make up for the evaporation.

If you notice your car is slow to turn over on a start and your headlamps or interior lights are dim, that might be a sign of battery damage. Another sign is a check-engine or battery light on the instrument panel. If you notice corrosion on your battery’s terminal posts or any bulges or cracks to the battery itself, those may also be indications of damage.

Consumer Reports recommends owners conduct electrical load tests every year after the first two years of a car used in a warm summertime climate, and after four years if your car is in a colder zone for any loss of voltage.

If your stock battery is toast, Consumer Reports also suggests investing in a more expensive absorbed glass mat (AGM) battery, which may give you much more operating life. Check with your car’s owner’s manual or consult a dealer to make sure they’re compatible with your car.

Ways You Can Help Save Your Battery

In the summer, parking in the shade can help avoid cooking your battery. Also remember not to run any lights or electronics with the engine off, as they will add to the drain.

If you can avoid taking trips of less than 10 minutes, that will avoid dipping into your battery’s power without the recharging processes that happen on a longer drive. Likewise, if you plan on leaving your car unused for an extended period, you may want to invest in a smart charger to keep the battery healthy.

Andy Stonehouse

Andy Stonehouse literally fell into the world of auto writing while working as a ski-town journalist, and has not looked back since. A childhood spent dealing with the eccentricities of a 1976 MG Midget has made any subsequent auto experience a more safe and reliable drive. He has been blessed with nearby mountain trails and snowy roads in Colorado to do TV-adventure-styled test drives on a weekly basis.