How to Prevent Heat Damage to Your Car Battery
As summer weather heats up, here’s how to keep your car’s power source in top shape.
Most people worry about their car batteries in winter, but it’s actually summer heat that does the most damage. High temperatures can dramatically impact the performance and longevity of this critical component. In fact, vehicle batteries in the southern United States on average last 17 months less than in colder northern climates, according to Consumer Reports.
The temperature outside doesn’t tell the whole story. If you’ve ever returned to a stifling-hot car after it’s been parked in the sun, that’s the greenhouse effect at work: Sunlight enters through the windows, turns into heat, and gets trapped inside. After 90 minutes, the inside of a parked car can be 48 degrees hotter than the outside air. The same process plays out under the hood, but things can get even hotter. The engine generates its own heat while driving. When sun-baked metal is added to the mix, temperatures can climb, exceeding 150 degrees in some parts of the country.
There are ways to minimize the impact of all that heat on your battery—and more importantly, catch battery failure before you're stranded. But first it helps to understand why heat takes such a toll on your battery in the first place.
Why Heat Can Damage Car Batteries
There are a number of ways that heat damages car batteries. However, according to Joseph Liedhegner, a director of engineering at battery maker Clarios, the “most common failure mode in lead-acid vehicle batteries is grid corrosion, where the internal metal grids that support the active material in the battery plates slowly degrade over time.”
Heat significantly accelerates this process by increasing the speed of electrochemical reactions, which causes corrosion and a breakdown of internal battery components. “Over time, this leads to reduced battery capacity, diminished starting power, and ultimately failure,” Liedhegner says.
Prevention: Before the Heat
You can mitigate the impact of summer heat on your battery before the season even starts. “Preventative maintenance before extreme heat sets in can reduce the risk of breakdowns,” says Chase Nacol, operations director for AAA Auto Repair. In the case of your battery, have it checked before the summer heats up, and then again after summer is over to catch any failure before winter weather.
“Have a professional check the battery’s voltage and conductance and inspect the terminals for corrosion,” Liedhegner says. Additionally, make sure nothing is blocking airflow under the hood, especially if you drive a newer car, since that flow is essential to keeping underhood temperatures where they should be.
Mitigation: During Hot Weather
When temperatures start to rise, the most important thing you can do to prevent battery failure is to park in a garage or shaded spot, keeping your car—and your battery—cooler. If shade or a garage isn’t an option, use a reflective windshield sunshade, which can significantly reduce temperatures in both the cabin and the engine compartment.
Routinely check your battery for any signs of corrosion, such as a blue powder on the battery terminals or swelling. Additionally, check the battery mounting brackets and confirm they’re tightly secured, to prevent damage due to vibration and extreme temperature swings.
If you live in a particularly hot part of the country, consider upgrading to an absorbed glass mat battery (AGM). AGM batteries are “better sealed and more heat-resistant than standard flooded batteries, which can also help improve durability,” Liedhegner says.
Electric Vehicles
Electric vehicles typically have two batteries: a standard 12-volt, lead-acid one that powers accessories, security functions, and startup, and a larger lithium-ion battery that powers the motor. Both are vulnerable because heat also takes a toll on lithium-ion batteries.
“Heat speeds up chemical reactions within the cells and contributes to degradation of the battery’s internal structure,” Liedhegner says. “Over time, this leads to reduced energy capacity, lower range, and potentially slower charging.”
EVs often have more advanced thermal management systems than traditional vehicles, he adds. Still, “prolonged exposure to high ambient temperatures can still cause long-term performance loss if not properly managed,” Liedhhegner says.
Interestingly, despite the impact heat has on electric vehicle batteries, Consumer Reports testing found that vehicle range is at its best on days when temperatures are in the mid-80s.
Parking in a garage or the shade is still important for electric vehicles. Also, consider charging your EV during nighttime hours when the temperatures are cooler. In EVs that have it, the “preconditioning feature—which cools the cabin while still plugged in—can help prevent the battery from overheating during use,” Liedhegner says. “Avoiding fast charging during heatwaves, if possible, can also reduce thermal stress on the battery pack.” Fast-charging is generally best left for situations where level 2 charging isn’t an option, since frequent use will affect the range of the vehicle over time.
While heat will certainly affect the life of your battery, preparing your car ahead of summer and taking precautions when temperatures are high will minimize the impact and keep your battery running for as long as possible.
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