One of the key concerns about running an electric vehicle (EV) in a hot climate is how the car will perform in warm temperatures. Motorists fear that overheating will, at minimum, adversely impact the performance and range of an EV, and at worst, cause a fire. But is there any basis for these suspicions?
Do EV Batteries Overheat?
Yes, but they are less likely to do so compared to traditional Internal Combustion Engine (ICE) cars, thanks to sophisticated cooling systems.
EV batteries typically operate best within a temperature range of around 20 to 35 degrees Celsius for optimal charging, performance and longevity. So hotter climates theoretically could negatively impact EVs.
However, while some EVs utilize air cooling (such as the Nissan Leaf) with vents and fans strategically placed within the battery compartment to circulate air, most electric car manufacturers now use liquid cooling systems. Known as ‘active thermal management systems’ the usually sealed units circulate a mixture of water and glycol to absorb the heat and release it through a radiator or heat exchanger.
Computer management systems on EVs monitor and regulate the temperature of the battery cells to ensure they operate at ideal temperatures. Some car makers also employ passive systems such as heat sinks or heat-dissipating materials within the battery structure itself.
A few EVs can even ‘precondition’ the battery before starting a journey. This is done by using the car’s heating or cooling systems to bring the battery to ideal operating temperature while it is connected to a charging station.
It’s also worth pointing out that EVs use regenerative braking (slowing the car using the electric motor which then converts kinetic energy back into electricity to recharge the batteries). Unlike conventional friction braking, this also reduces heat generation, thereby reducing the risk of overheating.
Nonetheless, like any car, extreme conditions, such as driving it very hard for extended periods in very hot climates can put undue stress on the cooling systems.
Do EVs Easily Catch Fire?
Videos and pictures of electric vehicles appearing to spontaneously self-combust are frequently shared on the internet, to the point they’ve left many motorists with genuine fears about the fire safety of electric cars.
However, according to data from the Bureau of Transportation Statistics and the National Transportation Safety Board in the United States, there are only 25.1 fires per 100,000 electric cars sold, compared to 1529.9 fires per 100,000 petrol cars sold. The highest number of fires are actually of hybrid cars at 3474.5 per 100,000.
Electric car fires do tend to hit headlines and get shared on social media as they are very hard to extinguish. The lithium battery produces a lot of smoke and can burn for hours. Firefighters need to get close to put it out, but due to the risk from high voltages, as well as the heat and smoke, they must maintain a safe distance.
In fact, some fire services use cameras to monitor electric cars that have caught fire, even when they have been put out, because lithium battery packs can actually reignite due to battery cells continuing to generate substantial heat.
Ironically this is made more difficult by battery packs in EVs actually being designed to be well protected and insulated, as it makes it extra challenging for firefighters to access and extinguish the source of the fire.
How Are EV Fires Caused?
EV fires can be caused by damage through collisions, manufacturing defects or improper maintenance. As battery cells contain huge amounts of energy this can result in a ‘thermal runway’ process where the battery’s temperature rises rapidly and causes a fire.
During charging, damaged cables, overheating connectors or electrical faults can lead to short circuits that could cause fires, as can the electrical systems onboard the car – although this is true of any car, not just EVs.
It’s important to note that on the whole, electric vehicle fires are still relatively rare compared to fires involving conventional vehicles as the data above proves.
Is a Hot Climate Bad for EVs?
Electric cars perform well in hot weather, but it’s also fair to say there may be some impact on performance, range, and the longevity of battery packs. Hot weather increases internal resistance of the battery, which can lead to slower charging times. There can also be limitations and a risk of overheating when charging, particularly utilising fast-chargers as they generate more heat.
Nonetheless, improved cooling systems on the most recent EVs are designed to mitigate these issues.
New Batteries Nail the Heat Test
Manufacturers are doing significant work to improve the heat-resistance and safety levels of EV batteries. Chinese company BYD (which stands for Build Your Dreams), one of the largest manufacturers of EVs in the world, has come up with new ‘Blade Battery’ technology.
The cobalt-free batteries are highly energy efficient and offer better thermal stability. However, the materials used in the Lithium Iron Phosphate (LFP) battery are less energy dense and take up more room. Instead of modules, BYD came up with a way of saving space by stacking the cells together as blades.
They then subjected the packs to extreme tests including nail penetration tests, as well as heating them to 300 degrees (a conventional lithium-ion battery burned at 260 degrees), and overcharging to 125 degrees. The LFP batteries were even put into a furnace and then driven over by a fully ladened HGV, just to be sure. The blade battery did not overheat.
So, the future seems cool then. Literally.
