How do electric cars work?

How do electric cars work?

Pretty much like most other motor-driven, electrical devices, actually. Most have more in common with, say, washing machines, than they do with cars relying on conventional petrol or diesel power.

While a fossil-fuelled vehicle depends on electricity and plumbing to make it work, an electric car just needs the obvious: electricity. At a stroke, it removes the need for involved and potentially troublesome water, fuel and oil systems. So there are fewer moving parts.

That makes it more reliable by design than a fuel-dependent engine: it also makes it more efficient. What’s more, because an electric motor can deliver consistent power across a broader range – think of the differing speeds that a washing machine turns at during a typical programmed cycle – it requires a much simpler gearbox than a conventional car’s. Typically, there are just forward and reverse gears. To drive, the car is similar to a conventional automatic, having just a brake and an accelerator plus a gear selector lever.

There’s more, too. The motor will be engineered so that, whenever the vehicle coasts or brakes, the engine acts as a generator, converting power taken from the turning wheels into electricity which it sends to the vehicle’s batteries, to be stored.

What is an electric motor, then?
At its centre is a tightly wrapped coil of wire that spins freely in a casing of powerful magnets. When electricity is fed into the coil, it generates a magnetic field, causing the coil to spin at varying speeds, depending on the current supplied.

As it works, it emits very little sound. For this reason Nissan and some other manufacturers have added sound generators to their cars, to keep pedestrians safe. We’re not used to vehicles that travel all but silently and we might otherwise unwitting step into their path.

Simply does it
An electric motor has, put simply, a lot less going on than a regular petrol or diesel motor. One that packs enough ‘oomph’ to propel a car could be fitted into a usefully smaller space, opening new possibilities in car design.

For now, though, designers have deliberately arranged what’s under an electric car’s bonnet to look as familiar as possible. Nissan says it took particular trouble with the Leaf to make the under-bonnet layout closely resemble what drivers knew from petrols and diesels. It had to look ‘right’. To do otherwise risked scaring off early adopters.

Aside from the motor itself, the car needs heavy-duty circuits and other components to manage and regulate electricity, converting it from direct current to alternating current as necessary and also to manage the voltage.

This includes the charging mechanics, which take power from an external charger or as generated via the motor itself and convert it into the right kind of electricity for the batteries to store.

There will also be a radiator and coolant. While electric motors generate less heat, they can and do get hot as they operate. To work at their best, they need to be kept at around 23 deg C.

Like in your laptop, only bigger
Then there are the batteries. Electric cars use lithium-ion batteries. Most are made of small cells linked together to form larger ‘modules’. Typically, up to 200 of these are linked together as a ‘pack’, offering sufficient storage capacity for up to 100 miles of driving between recharges. Tesla, however, uses much smaller modules – similar to those that power your laptop. But where your computer requires 6 or 9 of these, their cars use 5000.

Batteries with enough storage for the job are large and heavy. To reduce the effect of that weight on the way that the car drives, they are mounted low and (usually) in a thin, wide block. In the Nissan Leaf, they are mounted under the floor, beneath the rear seat and boot floor. This keeps the car’s use and internal size and layout close to what drivers expect.
Even so, you’ll still find a ‘regular’ 12v car battery under the bonnet – to power the starter, lights and other controls, just as it would in a petrol or diesel car.

At present, battery storage capacity limits the range of most models to little more than 100 miles, although that maximum drops if the car is driven a lot in stop-start traffic, in the dark and/or with the air-con and heating on the go.

A growing network of fast charging points, notably at service areas on major motorways, promise an 80% charge up after 30 minutes. But a technological breakthrough is needed before this restriction can be lessened.

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