Updated on August 19, 2026 by Joan Pinto | Originally written: August 3, 2021 by Liam Lahey

Optimal operating temperature for a car battery is about 25 degrees Celsius. Summer heat can drive up internal temperatures under the hood to above 65 degrees Celsius, which can be tougher on your vehicle and its battery than the cold grip of winter. High temperatures can overheat your car’s battery, weaken its charge, and lead to structural damage and corrosion.

Car batteries are designed to last from three to five years. Getting your battery inspected by a certified technician as part of your vehicle’s routine maintenance is essential, especially if you’re planning a family road or day trip before summer winds down.

Why car batteries can deteriorate and fail in summer

Summertime heat can trigger several problems that tend to deplete a gas-powered car’s lead-acid battery charge and lead to its failure. Extreme heat impacts to a car battery include:

1. Evaporation. Vehicle batteries need electrolytes (water and sulfuric acid) to fuel an internal chemical process needed to operate properly. In extreme temperatures, electrolytes evaporate, and inevitably, the battery will begin to malfunction.
2. Sulfation. Sulfation occurs when lead sulfate crystals build up and remain on the surface of battery plates. As a result of sulfation, a battery is deprived of a full charge and impedes the chemical to electrical conversion required to operate smoothly. Over time, sulfation dramatically shortens battery life and is the no. 1 cause of early failure in lead-acid batteries.
3. Corrosion. High temperatures and evaporating electrolytes trigger oxidation, which leads to a battery corroding faster than under normal conditions.
4. Overcharging. High heat causes your battery charging system to malfunction, resulting in overcharging. Similar to any electronic device such as your mobile phone, overcharging will reduce the lifespan of your vehicle’s battery.
5. Draining. Overheating can cause your battery to discharge faster, leading to eventual failure. 

Does summer’s heat affect electric vehicles?

Yes—summer heat can accelerate degradation in EVs that use lithium-ion batteries and temporarily affect battery performance and charging. It’s recommended to park your EV in a shaded area whenever possible. If you use a public rapid-charging station, try to find one in a shelter or opt for a slower charge. When you are powering up your EV in hot weather, refrain from charging it to the max on a regular basis or the battery may get too hot. Overheating can accelerate your lithium-ion battery’s cell degradation, resulting in lower capacity to recharge.

Does your vehicle have the right battery?

If you’re thinking of buying a new battery for your vehicle, start by checking your owner’s manual to ensure you purchase the right battery for your vehicle model. Most gas-powered vehicles use either a traditional lead-acid battery or an absorbed glass mat (AGM) battery.

A standard flooded lead-acid battery uses a liquid electrolyte for the chemical reaction but needs regular maintenance. Newer technology AGM batteries use a special glass mat material that absorbs and holds the electrolyte, eliminating need for a liquid. AGM versions are maintenance-free and can be mounted in any position, more resistant to vibration and shock.

Here are the differences and advantages of an AGM battery over conventional flooded lead-acid versions:

Source: Pluginhighway.ca

AGM batteries typically cost 40–100% more than comparable conventional batteries.

You can recycle an old lead-acid car battery. Bring your discarded battery for disposal to the repair shop or retailer from where you purchase a replacement. Be mindful of safety precautions outlined in your vehicle owner’s manual if you are going to remove and transport a dead battery.

How to protect your car battery through high temperatures

CAA, AAA, and consumer advocacy groups offer the following tips to help ensure your battery and car run optimally through summer months: 

• Have your car and its battery regularly maintained.
• Keep your car cool by parking in a garage, carport, or under a canopy. If these are unavailable, even a large tree can provide shade needed to keep cool. Window coverings can help keep the cabin of your car cool too.
• Clean the top of your car battery and connections to prevent discharge. 
• Check your battery regularly for corrosion or other damage and address issues promptly.
• Ensure your battery is secure as excessive vibration can damage internal components and shorten battery life.
• Flush your cooling system with fresh coolant periodically. Coolant can become acidic over time which can eat away at hoses and seals, leading to an overheated engine.
• Keep an eye on your vehicle’s air conditioning. If your car AC is not maintaining interior temperatures below a threshold well, its refrigerant level could be low. Have a certified technician inspect your air conditioning system.
• Ensure your tire pressure matches your car manufacturer’s recommendations. Driving with improperly inflated tires can affect your vehicle’s handling and braking, and cause tires to overheat, increasing your chances of a blowout.
• Stay on top of scheduled oil changes.
• Proactively replace your battery every 4–5 years.
• Try to drive regularly to ensure your battery doesn’t discharge. Trips of 20 minutes or longer can replenish your battery.
• For EVs, consider charging after dark when temperatures are cooler and avoid fast charging when during heatwaves.

Taking time for preventative battery maintenance can maximize your vehicle’s performance during summer months. 

Your car insurance needs checkups too

Like your vehicle and its battery, your car insurance needs attention as well. Compare insurance quotes today to find the best price for the type of coverage you need.