A fact that is drilled into our heads from a young age is that electricity and water do not mix. So your amazing plan of cooking toast whilst in the bath is not something you should attempt! But this raises the question of whether electric cars are safe in flood water type situations, or even whether they can go through puddles on a rainy day?

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Conventional fossil-fuel cars in flood water

Before we delve into how electric cars fare in water, it’s worth backing up and thinking about conventional fossil fuel powered cars. We know that driving them through water is discouraged, and this is due to a few reasons:

  1. Water getting into the engine (for example via the air intake pipe at the bottom of cars) can destroy the engine quickly.
  2. Water entering the transmission/gear mechanism (for example via transmission vent) can cause the transmission to pack up and not work properly.
  3. Water getting into some of the car fluids/oils (such as brake fluid and engine oil) can harm multiple systems of the car.

Flooding a fossil fuel car when driving through deep puddles or flood water is easier than you might imagine, due to the various fluids and intake valves/pipes that are needed for an internal combustion engine to operate.

Are electric cars different to conventional cars in deep water?

We know that electric cars don’t have an engine, they have less fluids/oils and they don’t have a complex transmission/gear system. So immediately the main risks of a fossil-fuel powered car are mitigated. But what about the battery pack, controller and electrical motor which make an electric car work?

Well in general, electric cars are fairly safe when going through deep water. The battery pack is sealed off, as is the drive train (e.g. the electric motor and controller). So electrocution isn’t an every day risk when taking an EV through deep water. Indeed, many electric cars have been driven through fairly deep water as part of their exhaustive testing. This water is deeper than most conventional cars could drive through, and the electric cars handled it well. We show videos of this in a following chapter, but Tesla’s Elon Musk says the following about Tesla car’s ability to deal with deep water:

Being able to function as a boat is fairly impressive! As they say, it’s not something they recommend - but it’s promising nonetheless.

It’s not just Tesla that have designed their electric cars to function better than fossil-fuel cars in flood water situations. The BMW i3 manual says:

“Drive though calm water only and only if it is not deeper than 9.8 inches/25 cm and at this height, no faster than walking speed, up to 3 mph/5 km/h.”

The battery pack of an EV is on the underside of the car and due to its weight/size, it’s fairly low to the ground. So the fact that the BMW i3 can go through a fairly deep 9.8”/26 cm level of water is positive and again suggests that the battery pack is sealed off.

The other benefit of an electric car is that (naturally) it’s full of electronic equipment and components - hence a range of safety checks can be carried out before full, high voltage is discharged from the battery to the other components. For example, the power management system inside the battery pack could detect if the battery is potentially unsafe and would simply not function if there’s a fundamental safety problem.

Risks of electric cars in floods

Whilst we know that electric cars tend to deal with deep water better than gasoline cars, it’s naturally not the case that EVs are flawless and always turn into a James Bond style boat when they touch water!

Lithium-ion batteries that make up an electric car’s battery pack can be dangerous if damaged by water, with explosion a real risk. Similarly, the high voltage electrical motor can also be dangerous if it’s water-damaged.

Whilst they are sealed off, very heavy flood water can sometimes get into these components - as a few prominent examples have shown:

  1. Rich Rebuilds is a car engineer who regularly buys flood damaged Tesla models and repairs them. He became famous for taking a flood damaged Model S (which he bought for $14,000) and repairing it slowly but surely:

    Rich dismantled the Model S he purchased and found that the battery pack had been sat in salt water for days and thus the battery pack was waterlogged. Despite this, 12 of the 16 battery modules were still functional - which is pretty good considering how destructive salt water can be to electrical components.

  2. Fisker Automative, the now-defunct electric car maker which wound-down in 2014, famously lost $30 million of their cars after Hurricane Sandy caused flooding and ultimately salt water damage to their 300 cars:

    “Fisker engineers determined that the damage to the Karmas was the result of the cars being submerged under five to eight feet of seawater for several hours that left corrosive salt in a low-voltage Vehicle Control Unit in one Karma. The Vehicle Control Unit is a standard component found in many types of vehicles and is powered by a typical 12V car battery. This residual salt damage caused a short circuit, which led to a fire that heavy winds then spread to other Karmas parked nearby.”

    5-8 feet of salt water is more than you can routinely expect your electric car to come across, and the whole Fisker situation was quite unfortunate (with a single car fire spreading to the rest of their fleet), but it nonetheless shows that electric cars aren’t perfect in heavy floods.

These two examples show that whilst the battery pack and electric drive train are waterproofed/sealed as much as possible, very deep flood water (4+ feet high, for example) - especially flood water with a high salt content - will almost certainly destroy an electric car. There’s practically no escaping this.

Finally, it’s worth noting that electric cars can drive through fairly still flood water (as we’ll see below), but things can become dangerous if it’s flowing water. Many cars, and especially electric cars, could simply lose their traction and be swept away by water flowing across a road.

Videos of electric cars going through flood water

Elon Musk’s tweet earlier was in response to a man from Kazakhstan who driven his Tesla Model S through flood water, using its thrust to push it forward through the water like a boat:

You can actually see the Model S go around a fossil fuel powered car that got stuck in this depth of water!

Secondly, a Nissan Leaf press conference from 8 years ago shown that the Leaf can handle water depths of 300mm to as high as 700mm:

This fairly impressive video shows water up to the headlight level, meaning the water depth is over 2 feet at times!

Finally, the BMW i3 and i8 have been tested going through (not too deep) water at quite high speeds, without any issue:

Summary

In summary, electric cars are generally better than conventional cars when it comes to dealing with excess surface water. EVs work in a less complex way that fossil fuel powered cars, meaning that some of the traditional risks with taking cars through deep water no longer apply. However it’s still recommended that you apply common sense and don’t go through flood water unless you really have to.