How Hot Weather affects your Car Battery

Have you noticed how during scorching summers, everything seems to give up easily? Even your car battery isnt spared from this heat. Lets discuss how the heat affects your car battery, and what steps you can take to avoid these issues. 

how hot weather affects your car battery - comment le temps chaud affecte t il la batterie de votre voiture

The effect of heat on your car battery

Did you know that heat is the ultimate battery killer? Unlike the below-zero temperatures in winter, which slow down the chemical reactions that power the battery, the summer heat can cause extensive damage. 

Even if you take care of your battery during the summer, the accumulated damage can cause it to die during the winter months. The intense heat not only evaporates the battery fluid needed to power the battery, but it also speeds up corrosion, putting your battery at risk of failure. 

Heat can worsen sulphation, a process that results in small amounts of lead sulphate remaining after you’ve charged your battery. Heat can exacerbate this process, further contributing to battery failure. Overcharging your battery is easier in the summer because the heat interferes with the charging system. Like all electronics, overcharging a car battery can decrease its lifespan. 

Your battery may experience a chemical reaction called thermal runaway during extreme heat. This causes the battery temperature to rapidly increase and can lead to total failure and, in rare cases, a fire. 

Heat-related battery failure symptoms

Your car may show signs that its battery is struggling in the heat. These include: 

  • Your car is having trouble starting. 
  • Electronic components, such as lights, A/C, radio, etc., aren’t working properly. 
  • The check engine light or battery warning light is on. 
  • The car battery case appears swollen. 
  • You can see corrosion on the battery pack. 

If you notice any of these symptoms, assess your battery right away. Sometimes, you may just need to jumpstart or charge your battery. If there’s severe corrosion or swelling, you’ll need a new battery. If you’re unsure how serious the damage is, have it assessed by a professional. 

Protecting your battery

To avoid a dead battery this summer, follow these maintenance and usage tips.


Give your battery a thorough cleaning every six months to remove any grime or corrosion buildup. Use a mixture of water and baking soda or a terminal cleaner and protector with a cleaning tool for this. Don’t forget gloves! 

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Power up

The optimal charge level for most car batteries is between 50% and 80%. If you drive four or five times a week, the alternator will charge your battery through use. If you won’t be driving for several weeks, top your battery up a little bit every two weeks so it’ll be ready when you need it. When possible, use a trickle charger for slow and steady charging. 

If your car battery is completely dead (but not swollen or seriously corroded), recharge it. 

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Damage assessment

Assess your battery for signs of damage, such as bloating or corrosion, at least twice a year. If your battery requires water, check the water level and top it up as needed. Most batteries that require water will have a label on them that says, “Non-Maintenance Free (NMF).” For AGM (absorbent glass mat) batteries, top up the battery fluid. 

If your battery is severely damaged or reaching the end of its lifespan (typically four or five years), you may need to replace it.

Keep it covered

Protect your car battery from the sun by parking in the shade, and if shade is unavailable, use a car cover to deflect UV rays. On hot days, avoid using electronic features like A/C, lights, and the radio when the car is off to preserve the battery. 

Best batteries for resisting heat

The best batteries for resisting heat are those with AGM (absorbent glass mat) technology. NAPA has a line of AGM batteries for all different vehicles, including passenger cars. 

NAPA’s The Legend Premium AGM Battery offers enhanced durability for better performance and longer service life than the average battery. It’s also able to start in challenging conditions that other batteries may crumble under, such as infrequent vehicle use, stop-and-start traffic, and hefty power drains from electronics. 

Use the “Add New Vehicle” feature on the top left corner of the NAPA website for a guaranteed fit on all automotive products, including the right battery size. 

For more advice on battery maintenance, refer to your owner’s manual or visit your local NAPA Auto Parts store to speak to an expert.

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