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Summer Heat is a Bummer


We get it. You’re probably sick of hearing about the heat. At the risk of driving you nuts, we’re going to take a look at the impact extreme heat can have on your vehicle’s starting system, with a specific focus on the battery. The one solace we can offer with this article is that we’re going to provide useful, actionable information that you can use to better manage your vehicle’s health. That’s much more helpful than what you get from the evening news, or at least we think so.

When most people think about weather impacting their vehicle, they immediately think about the cold and snow. This is only natural. After all, we’ve been raised on footage of places like Syracuse, NY and Duluth, MN, with snow banks higher than SUVs and frigid temps. It’s true that extreme cold can be problematic, but prolonged extreme heat is actually more harmful to your battery’s health than cold. Ask anyone who lives in Las Vegas or Phoenix how long their typical vehicle battery lasts. (Hint: Not long.) Read on to learn more about the effects of extreme heat on your vehicle, as well as to learn some tips about how to mitigate some of the risk from extreme heat.

A Quick, Smart Overview

We’ll start with a great general purpose introduction to this topic from the website of Chapel Hill Tire Company. They do a nice job of explaining how extreme heat can cause battery deterioration and how summer heat damage can actually show up months later in the form of a dead winter battery. “The damage of the summer heat will stay with your car battery long after the weather cools down. In fact, the summer heat is often responsible for battery failure in the winter. Many car batteries die in the winter—and drivers mistakenly blame the cold weather. But the cold temperatures do not actually damage your battery.”  They then go on to list 9 things to consider as you battle the detrimental effects of extreme heat. It’s quick and informative.

How Hot Weather Affects Your Car

The folks at Consumer Reports also took a swing at this topic and, as you can imagine, they present a very comprehensive analysis of the subject. Surprisingly, this great article is accessible without being a member. As with the above article, they start by dispelling the myth that winter is the only dead battery season. AAA reports that it responded to 2 million battery-related service calls in the summer of 2022.

The article then goes on to discuss different aspects of battery health and battery performance characteristics. They even provide a nuanced view of the benefits of AGM batteries, which they say have tested better in extreme heat testing (We have seen that most of the AGM batteries excel in our heat-focused life testing, based on 15 weeks of continuous testing at over 160 degrees.). But, they also note that the fact that, because AGM batteries are totally sealed and therefore cannot have water added to them, their lifespan could be diminished due to excessive heat. In other words, it’s a complicated picture.

They also provide some tips for managing your batteries for optimal health, as well as preventive maintenance suggestions related to batteries. Here, they provide some key action items worth emphasizing. First, they taut the value of a quality battery load test. “… [they recommend] having your car battery load tested annually after it’s 2 years old if you live in a warmer climate or after it’s 4 years old if you live in a colder climate. Doing so tests its ability to hold voltage while being used, and the results will let you know when it’s time to start shopping.” Very helpful advice. They also caution against changing your battery type when it’s time for a replacement. As they note, your vehicle’s charging system may be optimized for a specific battery type, such as an AGM battery. Installing a different battery type as replacement could result in a one-way ticket to the land of unintended consequences.

It makes for a great read and is full of useful, accurate information.

Arizona Has Something to Add

People in Arizona face some of the hottest temperatures in the US each year. The folks at put together a piece for their readers listing steps they could take to combat the negative impact of extreme heat on their vehicle. Their list of things to watch for extends far beyond the battery and starting system, with a focus on such things as engine temperature, cooling system performance, tire pressure and maintaining proper fluid levels. All great suggestions.

They also provide several tips for driving in extreme heat. Some of these match the types of tips you get for driving in the cold – don’t let your gas tank get too low. Some mirror typical cold weather tips – have cold water, sunscreen and an umbrella (vs. hot liquids, a blanket and a shovel). Others are really helpful for those not used to experiencing the extremely high temperatures of recent years – don’t pull over in area of high undergrowth because your catalytic converter can start a fire in that undergrowth. As a city boy from Chicago, that’s a new one on me.

That’s Fine and All, But What About EVs

This is the question recently asked by writers at the LA Times. They quickly note the irony that vehicles designed to help the world combat climate change actually don’t fare well in the temperatures brought about by climate change. They state that, although extreme heat isn’t going to kill your EV outright, it is likely to reduce the EV battery’s performance over time. On a chemical level, though, extreme heat is akin to heart disease for EV batteries, or a slow-moving form of cancer. Plus, of course, every EV also has a low voltage battery paired with the EV battery, which certainly is sensitive to extreme heat, as noted above.

One of the things the article points out is that, even though winter cold will reduce your EV range in the short term, it is unlikely to impact the EV battery’s capacity over the long term. Conversely, the damage done by extreme heat can result in a reduction of EV battery capacity such that maximum range is permanently reduced. That’s a frightening concept. They explain that extremely hot temperatures result in overexcitement of the high voltage battery’s chemistry, resulting in microscopic damage to the battery’s internal structure, which over time can accumulate enough to impact its health and performance.

The article makes the case that, when it comes to selling an EV, battery health is now one of the key factors for potential buyers. Stephanie Valdez Streaty, director of strategic planning at Cox Automotive Inc., said 4 out of 5 EV shoppers now consider battery longevity when buying, which is one reason her team is working up a proprietary score to measure it.” So, taking steps to avoid long term damage from extreme heat could be that much more critical for owners of EVs. In know, one more thing to worry about, but having this knowledge can help you to avoid the worst consequences of extreme heat.

Well, that wraps up our look at the impact of prolonged exposure to extreme heat on your vehicle. It is a little surprising that we’ve never addressed this topic before. We promise that, no matter how hot it gets in August, we won’t be talking about the heat in our next newsletter. By then, we’ll all surely be tired of hearing about it.

How about you? Do you live in a place, like Phoenix or Vegas, where you need to be concerned about the impact of consistently hot temps on your vehicle? Or, you have specific strategies to deal with extreme temperatures, hot or cold? Are you a shop or technician that regularly sees heat-impacted vehicles and have tips to share with our audience? We would love to hear about it in the comments below.

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