For those of us in the northern hemisphere, summer will soon be upon us. With temperatures in some parts of the U.S. now set to stay in triple digits for the next few months, heat waves already hitting parts of Europe, and the need for a jacket now a distant memory for many, we’re now officially heading into the last few weeks of spring.
For those of us in more temperate climbs towards the more northerly parts of Europe, Asia or North America, that means enjoying the extra light of a long midsummer day, not having to wear a coat or jacket, and perhaps taking in a few extra road trips. For those further south, where heading outside between 10 am and 3pm is like stepping into an oven, it can mean leaving the air conditioning on all day, and staying as cool as possible during the midday sun.
Like us, electric and plug-in hybrid cars aren’t fans of extreme heat any more than they are fans of extreme cold. And while your electric car will work just fine when the temperature is pushing 110 degrees, there are a few things that you can do to keep your electric car happy and its battery healthy during the hottest parts of summer.
(We should note too that the advice in this article is intended for those in areas where the daily temperature exceeds 100 degrees fahrenheit (37 degrees Celsius). If you live somewhere with cooler summer temperatures, the likelihood is that your car will be just fine.)
Heat is the enemy
Like us, electric car battery packs prefer a temperature of between 60 and 85 degrees fahrenheit in which to function. Go much beyond that in either direction and bad things happen. In the winter, a cold battery pack has a higher internal resistance, meaning it’s harder for the battery pack to give up its energy for high-current applications — such as accelerating an electric car.
At the other end of the spectrum, if a battery pack gets too hot, it suffers something called premature ageing, where the extreme heat causes the surface of the electrodes to warp, slowly losing their ability to hold a charge over time. This happens naturally in more temperate climates, but the hotter the battery, the quicker this happens.
To prevent this from happening, some electric cars have built-in thermal management systems which circulate coolant around the battery pack to keep the battery pack at a more comfortable temperature. Others use a similar system based on air conditioning. If your car uses either, check coolant levels before the summer sun bites to ensure they’re operating aa maximum efficiency, because just like a gasoline-engined car, plug-in cars need cooling in the summer to keep them happy.
Park in the shade
While most electric car battery packs are located on the underside of the vehicle, they can still be the victim of direct sunlight on a hot day. Moreover, because electric car battery packs tend to have a fairly large thermal mass, they can stay warm for many hours after being heated up to a high temperature.
As a consequence, it’s best to try and keep your electric car out of direct sunlight wherever possible, parking underground or in a garage whenever you can.
It’s worth noting too that in sun-exposed parking lots, the ground can be in excess of one hundred degrees if it has been in direct sunlight for a while. This means even if the space is no-longer in direct sunlight because the sun has moved, the ground beneath your car can still transfer a lot of radiant heat to the underside of your car and thus the battery pack if it has previously been in direct sunlight.
Stay plugged in when possible
If your car is one of the many electric cars on the market to use liquid-based cooling, keeping your car plugged in to a charging station will make it possible for the car to use mains electricity to power its battery cooling system. While not all cars have this feature, it can help ensure a long battery life in cars which do.
As a side bonus, keeping your car plugged in means in most cases that you’ll be able to operate your car’s air conditioning remotely, ensuring that the car is at a comfortable temperature for you when you return.
Avoid rapid charging marathons
Rapid charging puts your electric car’s battery pack under a much greater strain than regular charging, since it it pushing far more power into the battery than a level 2 or level 1 charge would.
While most electric cars on the market today can happily cope with a single rapid charge on a hot day — and will actively slow down rapid charging if the battery gets too hot to protect itself — planning a mammoth road-trip on a really hot day where you’re asking your car to drive and charge multiple times in quick succession without giving it a chance to cool down is a bad idea.
That’s because the act of rapid charging a battery tends to raise the temperature of the battery, especially towards the last twenty percent of a quick charge cycle. If your battery is already hot, quick charging simply raises that temperature further, putting your battery — and its cooling system — under extra strain.
*A quick note for Mitsubishi i-Miev users: when rapid charging, the i-Miev blows air from the battery pack into the cabin in an attempt to keep the battery pack cool, but it has the unfortunate side effect of heating up the cabin. As such, if you’re rapid-charging your i-Miev on a hot day, it’s best to stay with the car — and wind down the windows unless you like stepping into an oven after charging has completed.
Avoid the turtle
Just as multiple quick charging cycles can cause additional strain on an electric car battery pack in the summer, so too can running the car to empty.
That’s because as a battery discharges, the higher the current from the battery becomes to make up for the slowly-dropping voltage. With modern battery packs and modern electric cars, that’s not an issue over the majority of the battery pack, but as a modern lithium-ion cell nears its empty limit, the battery voltage starts to drop dramatically, causing a spike in current to keep the same power level flowing.
That higher current flow — and an increase in internal cell resistance as the pack nears empty — increases the temperature of the battery pack.
Luckily, most electric cars won’t feel the burden of a low-voltage situation until the car has passed its low battery warning or even its very low battery warning (that’s one of the reasons that automakers put such warnings in the car).
But if you want to be super-kind to your car, avoid draining your car’s battery below ten miles or so of remaining range when the temperature outside is high.
We’ve built this list based on the collective twenty-five years of plug-in ownership of our editorial team. But we’re keen to hear your experiences too.
Do you help your plug-in car cope with summer temperatures in a different way? Or do you just deal with the weather without batting an eyelid? Or perhaps you’ve suffered from premature battery ageing and want to share your experiences? Leave your thoughts in the Comments below.
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