"A Closer Look At Regenerative Braking"

All electric vehicles (EVs) have the potential for regenerative braking. Any electric motor can become a generator producing power which decelerates the vehicle and recharges the battery. Some motor types are better than others, fortunately the permanent magnet synchronous and induction asynchronous motors commonly used in EVs are fairly good. The attached article covers regenerative braking including details on the efficiency (not very good) and the benefits. One significant benefit (for some drivers) that is only lightly covered in the article is one-pedal driving.

Regenerative braking is not new, it was used on some electric trolleys in the early twentieth century.

A Closer Look At Regenerative Braking - Charged - Sep - Oct 2018.pdf (3.9 MB)

Regen reduces the sensitivity of the energy used by the vehicle to mass by about 50% in urban driving. The ‘problem’ with regen is that if you want to abandon mechanical brakes you have to size your electronics to cope with 1g, approx, retardation, which especially at high speed is a big ask. So that’s why mechanical brakes aren’t going away any time soon. On the plus side 95% of braking events are at 0.3g or less, so you can use regen only quite a lot of the time.

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With a manual transmission, one can slow down the vehicle by down shifting. Not regen, but another way of slowing down.
Also good in ice in that it will not lock up the wheels.

That scares me a little. With drivers becoming accustomed to not having to use the service brakes I suspect they’re going to be a bit slower to get on them when it does start to matter.

Separately is the matter of hand-off from regen to service braking and how that would affect drivers who are accustomed to doing all of their own brake modulation.


You are talking about the one foot control? Yes, I’m very interested in how they’ve implemented that.

Yes, one-pedal driving. I know there are people who really like it, but they sound like people who would prefer to have as little to do with their own driving as possible. At least under some circumstances (heavy traffic, long trips).

Supposedly in some vehicles you can dial in the amount of regen, which to a completely analog driver like me seems way too fiddly.


I don’t know why that scares you a little. I have seen many cars on the road with more than on break light not working.
In the older cars, if the light was out the turn signal did not work. The newer cars are not wired like that.

The first time I asked for an oil change, on my newer car, I also asked for a lamp check. The service guy was very confused, and said that is the first time anyone asked for that.

So bottom line is don’t tailgate. Besides the older cars did not have a center break light.

All EV manufacturers are aware that many drivers don’t want regenerative braking. There is a control setting (typically the default mode) that has just enough regeneration to mimic engine braking for an Internal Combustion Engine (ICE). Most of the EVs also have controls where the driver can select different driving modes, such as , “Sport”, “Normal”, and “Economy”. The choice made has a slight effect on regeneration… more regeneration being used for “Economy” mode.

The way one-pedal regeneration is implemented varies by manufacturer:

Some don’t even offer it (at this time). An example is the new Volkswagen ID.4. This model has several levels of regeneration that the driver can choose (or not choose). Other than the minimal amount (see above), regeneration is engaged when the driver first touches the bake pedal. Push on the brake pedal with more force and the typical hydraulic brakes engage, in addition to regeneration.

Chevrolet Bolt (my car), has two selections, one labeled “D” which mimics and an ICE (see above). The other selection is labeled “L” which is effective, but modest one-pedal driving. For maximum regeneration, there is a “paddle” mounted under on the underside of the steering wheel. The paddle can be easily pulled with left hand fingers. This maximum regeneration can be used in both “D” and “L” modes. Step on the brake pedal, you get hydraulic brakes along with regeneration.

The current Nissan LEAF has a some regeneration (see above), but also a “button” that can be pushed to put (and keep) the car in one-pedal mode.

Hyundai Kona EV, has minimal regeneration (see above) plus two paddles under the steering wheel. One paddle is pulled to select any of three additional regeneration levels. If this paddle is held then released, one-pedal driving is engaged. The second pedal is to cancel increased regeneration and return to the default mode.

I expect Tesla and others have there own version of one-pedal driving, but I can’t speak to that. In four years of driving both an older Nissan LEAF and a Chevy Bolt, I can say with certainty that using increased regeneration does take a little while to get use to, but is easier to do than to explain.

This mode makes sense to me, as it is analogous to an engine brake (jake brake) on a diesel truck engine.

@btrueblood I really like the paddle, my wife never uses it. It does take a while to get use to coordinating your left hand with your right foot.

Hmm, yeah. A skill to learn, like all the others. Driving a Brownie transmission, or a split-axle 5-speed, with a jake brake and trailer brake controls…takes some skill (my dad and brother, not me, I ran the gasoline engined trucks). So does playing good jazz on a piano (my aunt, and my #2 son) with one hand doing the bass line, and one hand riffing improv (and sometimes they cross over), pedals and coordinating with the rest of the rhythm section… :+1: :slight_smile:

There has been a new development in Jake brakes.
The HPD Jake, High power density.
Traditional Jakes worked by opening the exhaust valve at the top of the compression stroke and releasing energy as hot gas.
The latest version then opens the intake valve and allows a new charge ti fill the cylinder.
The exhaust valves are held closed during what would normally be the exhaust stroke.
When the valves are opened at the top of the exhaust stroke energy in the form of hot gas is again released.
This has almost doubled the maxim retardation of the Jake brake.
(The Jake brake, invented by Clessie Cummins, but manufactured by Mr Jacobs of the Jacobs Three Jawed Chuck.)