The Built-In Defect, by Eric Peters

There’s only one teeny tiny little problem with electric cars: sometimes they spontaneously combust. And the fires are hard to put out. But other than that, they’re perfect. From Eric Peters at

The infamously exploding Ford Pinto was recalled because of a design defect with the Pinto. That particular car. But cars – as such – weren’t defective, so only the Pinto was recalled for its proclivity to burn when hit from behind.

But electric cars have this defect designed into them.

All of them.

And unlike with the Pinto, you don’t have to get hit – or hit anything – for an electric car to burn. The things can – and have – caught fire when parked. Actually, “caught” is not the right word to describe what happens.

Spontaneous combustion is better.

It is because of the nature/design of electric car batteries, which are not like the small 12 volt battery that starts the engine of a not-electric car. That battery is generally lead-acid and fires are very rare because it requires at least two predicates: A spark – as caused by jumper cables contacting the battery’s terminals – and leaking hydrogen gas. If both of those predicates aren’t present, a 12 volt starter battery fire is highly improbable.

It’s almost unheard of nowadays because almost all 12 volt starter batteries made since the ‘90s are sealed. Hence, no gas can escape, all-but-eliminating the possibility of a fire ignited by a spark during a jump-start operation.

You can break the case of a 12 volt starter battery and it will leak – but not burn.

Electric car batteries, on the other hand, are very high voltage batteries – 400 volts is typical; 800 volts is becoming common – and they are fire-prone by design.

A process called thermal runaway can trigger a fire without a spark – or an impact. This most commonly happens when the electric car is being charged – and it is why electric car fast-charging is always a potential fire problem.

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2 responses to “The Built-In Defect, by Eric Peters

  1. A lot can be learned from the experience of ‘modellers’.
    They’ve been using battery technology to facilitate electric flight, for quite a few years; specifically Lithium-Polymer.

    I’ve personally seen two models spontaneously combust, after having (presumably) suffered problems with their speed controllers. One of these incidents occurred while the model was flying … as you say “you can’t put out the fires”. A third model burst into flames after a crash, burning very fiercely after the battery was ruptured.

    Modellers are generally well-aware of the risks, and often store/charge their batteries in metal containers, to mediate the risks. Ammunition boxes are some of the favorite choices.

    In spite of these precautions, tales of homes lost to ‘battery-charging’ are fairly common.

    Modellers are also aware of the practical failings of battery technology.

    These include:
    power-density … you get a lot more energy out of a pound of fuel, than a pound of battery.

    “fade” … full power is only available early in a flight. As energy is consumed, the battery becomes unable to provide the demanded power. An IC engine remains capable of producing its full power, for as long as there is fuel in the tank.

    temperature … electric flight is a bit of a nightmare in cold temps. Peeps resort to stuffing batteries down their trousers, to keep them warm, A cold battery is seriously compromised.

    OTOH, electric flight does provide some advantages to modellers, which are deemed by many to be sufficient to outweigh its shortcomings. Among these are quietness, cleanliness and reliability. Electric power is also very suitable for small models; in fact, this is where it excels.


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