Is a battery electric vehicle safe in a flood? | The Driven
electric car in flood

We are encouraging questions from readers about electric vehicles, and charging, and whatever else you want to learn. So please send them through and we will get our experts to respond, and invite other people to contribute through the comments section.

Our latest question comes from Andrew, who asks:

I know this is not high on everyone’s list of things they want to do, but it happens. So do BEV owners need a strong education program to NOT do this?

And if one did do this, what would happen – electrically speaking, eg, water in the battery, water in the motors (especially those located adjacent to wheels), short circuits galore, electrocution?????


Many people reading this article will have seen press images of vehicles floating down main streets, or people caught on a flooded road. As the authorities say, you shouldn’t drive into any flooded road, whatever car you are driving.

So the question arises as to whether an electric vehicle (EV) floating down said main street is any more dangerous than the petrol and oil leaking from a petrol car with a potential 12V ignition source floating alongside it …

So how does an EV respond/is made safe in this situation?

First of all, there is the IP (International Protection) rating system that EV electrical components must comply with. (The IP rating is listed on many things we buy, but few of us take much notice of what it means).

A typical IP rating would be ‘IP65’ – the first number (6 in this example) refers to sealing against dry stuff getting in (eg fingers, dust) and the second (5 in this case) refers to water getting in. IP65 means the item is totally sealed against dust entering and is protected from low pressure jets of water from any direction.

EV electrical components, in particular those in the high voltage sections of the motor, speed controller and battery, are rated to IP66 or better. A 6 for water entry means ‘protected against strong jets of water’. (BTW: an ‘8’ is the highest water entry rating and is basically the water entry rating you would want for a submarine!)

Also, in most modern EVs the motor, speed controller and batteries are actually water cooled to ensure their longevity by maintaining an even temperature at all times – so an IP water entry rating of ‘8’ for these would be mandatory.

So the first part of the answer is that where an undamaged EV is floating down a flooded road or river, its electrical components are well sealed and extremely unlikely to provide an electrical hazard to its occupants, bystanders … or passing fish ….

A second part to the question does however present itself: what happens if the EV is damaged and sections of the high voltage electrics become exposed?

In this case, a series of safety and protection systems will kick in. In the event of a crash, automatic disconnection of the high voltage electrics occurs through an impact sensor (which exists in all modern cars), thereby limiting the presence of high voltage to within the battery only. Another system (called a ground-fault detection system) is also built into EVs.

The ground-fault detection system constantly tests for electrical connections between the metal vehicle body and the high voltage system. (The two must at all times remain isolated from each other). On detection of such a fault, the ground-fault system will shut-off the electrical supply to the high voltage components. Additionally, there are a series of fuses inside a battery pack to disconnect different areas within the pack if needed.

Summing up: all EVs are designed to meet international standards on water ingress and as such should be safe in a flooded situation. They also have a variety of safety systems designed to minimise the likelihood of an electrical short-circuit or potential for electrical shock in the event of a crash or where a shock-hazard is detected.

If you need further proof – watch this 2016 video here, of a Tesla ‘swimming’ its way through a flooded tunnel in Kazakhstan. Whilst something Tesla definitely does not condone/recommend, it is testament to the sealed nature of EV electrics vs the way patrol/diesel cars quickly drown in the same situation!

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