Dear Car Talk:
Is the idea of downshifting when going down a hill outdated for hybrid vehicles with regenerative braking?
I grew up with the idea that one should always downshift on long downhills to avoid brake wear and overheating the brakes.
Now, I have a 2021 Toyota Camry Hybrid. There's a monitor on the dash, and when I brake going downhill, it tells me I'm getting the benefit of regenerative braking, which recharges my battery.
When I downshift going downhill, I don't see any regenerative charging happening. What I don't know is the effect on the brake wear and overheating. To downshift or brake...
What's a hybrid owner to do? Love the column. -- Chuck
Use the brakes, Chuck.
Regenerative braking does two things. It uses your already-spinning wheels to turn a generator that makes electricity. And because it takes effort to turn that generator, it slows down those wheels, reducing the speed of the car. So when you use regenerative braking, you're not only making electricity and increasing your mileage, you're also slowing the car without using -- or wearing out -- your traditional "friction" brakes.
If your friction brakes are being used lightly, or hardly at all, there's almost no chance they'll overheat your brake fluid and cause brake failure -- which is the danger when you brake constantly while descending, say, Pike's Peak. Now, if the regenerative braking is insufficient to slow the car and you step harder on the brake pedal, your car will add in friction braking. But those friction brakes will still be doing a lot less than they would if they were your only brakes. And there's really no danger of overheating or wearing out the regenerative braking system.
It's true that once your battery is full, you won't be able to use regenerative braking, because, simply put, there's nowhere to put the electricity you're making. But in a hybrid, your battery won't be completely full when you're coming down a hill. How do we know that? Because you just went up the hill and used the battery.
I suppose in a fully electric car, if you stopped at the top of a mountain and then charged the battery, you might then need to use friction braking on your way down. So keep that in mind, ski-chalet-owning Tesla drivers. But in the real world, that's not going to be a problem.
So, the answer is to just drive it, Chuck. Use the brake pedal to slow the car as much as necessary and reap the benefit of better mileage and less brake wear.
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