In school I learned that braking is a waste of fuel as the kinetic energy transfers to sound and heat (which is effectively a loss, right?). So how does regenerative braking recoup some of that energy into the car’s battery?
In: Engineering
An electric motor is basically the same thing as an electric generator. One turns electricity into something rotating and the other turns rotation into electricity.
Regenerative braking is when you break by having the turning wheels of your car drive the generator to charge a battery.
You might be familiar with the concept if you ride a bicycle that doesn’t come with a battery powered light. Many bikes generate the electricity to power their lights with a small dynamo that rolls along the sidewall of your tire. Using this you can create electricity from just your bike moving forward, but it makes it a slight bit harder to pedal and if you just let your bike roll along without pedaling the dynamo makes it stop earlier.
If you scale this up enough you can have a dynamo that slows down the wheel so much that it acts as a break.
This way you charge your battery up a bit every time you break. It means less wasted energy as normally the energy would just be converted into heat when breaking and lost.
In city traffic where there is a lot of stop and go it can make a rather big difference.
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