Does regen braking use more power? [Update: no, it does not]

[khamilton6]

I guess the question should be does regen braking use more of your battery. Maybe it's all in my head, but just seems like it is putting a strain on the motors, kinda like pressing the gas with the brake applied in a car...
Might be a stupid question, so you can roast me if you want. I am sure there will be at least a couple.
Thanks!

 

[SigNC]

it uses the motors to put energy INTO the battery. using your mechanical brakes wastes energy in the form of heat while regen braking leverages the motors to recapture a high percentage (~85% i believe) of the energy. So best case for efficiency you don't brake, 2nd best is regen braking, worst case is mechanical braking.

Oh and no roasting, if you don't ask you won't learn.

 

[derekmw]

Here is a cool video on how much energy gets generated by regen. Think of it like those wind up flash lights for emergency use. You know how you feel the resistance when you're winding it up? You're actually generating electricity there, charging up the batteries to power the light.

 

[toolman335]

Since you opened yourself up to potential roasting, you won't get roasted lol

The entire point of regen braking is to lessen the load on the brakes while sending energy back to the battery.

There's a youtube video of a tesla being dead on a track. A tow truck tows it around for a lap and the battery gained power due strictly to regen braking.

 

[toolman335]

derek great minds think alike lol

 

[jerry33]

This is somewhat similar to the "Don't use the gears to slow down because you'll wear out the engine and transmission" school of thought. Transmissions and engines have a very long lifespan (unless you compare them to electric motors). Regen braking puts energy back into the battery and also saves wear on the friction brakes. Now, having said that, there are energy conversion losses associated with regen braking, so you don't get the full amount of kinetic energy put into the battery. Coasting to a stop gets more work done from the kinetic energy than regen but is not practical in most situations. Still, regen is far better than throwing 100% of the kinetic energy away through the use of friction brakes.

 

[1.21GW]

Acceleration uses energy from the battery

Deceleration recovers energy

• Using Brake Pedal - Turns energy into heat in the Brake Rotors
• Using Regen - Turns energy into electricity that can be stored

The life rating of the motor and other electronics are designed for use of regen for the life of the vehicle. Or as Elon has shared, 1 Million Miles

 

[ewoodrick]

It indeed produces more stress on the motor, but motors often tend to last forever.
The recovered power is huge though. And all of this is factored into today's estimated 300,000 mile life of car

 

[Garlan Garner]

I guess the question should be does regen braking use more of your battery. Maybe it's all in my head, but just seems like it is putting a strain on the motors, kinda like pressing the gas with the brake applied in a car...
Might be a stupid question, so you can roast me if you want. I am sure there will be at least a couple.
Thanks!

I don't think Tesla ( or any other manufacturer ) would have come up with regen if it strained the motors or something like that.

 

[SSedan]

To me this question is a glaring damnation of whatever schools you attended and being here I will presume you have some degree above HS.

The kinetic energy of the car has to go somewhere, as others have said standard brakes convert it to heat which is she'd to the air.
REGENERATIVE BRAKING, as the name flat out states is recovering that energy for use again.

Using critical thinking skills if regenerative braking consumed more energy where is that energy going? It can't just vanish.

 

[jerry33]

To me this question is a glaring damnation of whatever schools you attended and being here I will presume you have some degree above HS.

The kinetic energy of the car has to go somewhere, as others have said standard brakes convert it to heat which is she'd to the air.
REGENERATIVE BRAKING, as the name flat out states is recovering that energy for use again.

Using critical thinking skills if regenerative braking consumed more energy where is that energy going? It can't just vanish.

More correctly, regenerative braking is recovering part of the kinetic energy for use again, what it doesn't recover is converted to heat. Of course, the total kinetic energy is the 100% value.

 

[Garlan Garner]

More correctly, regenerative braking is recovering part of the kinetic energy for use again, what it doesn't recover is converted to heat. Of course, the total kinetic energy is the 100% value.

hmmmmm…looks like you went to a better school. lol

Anyone go to an even better school?

 

[khamilton6]

Thank you for the replies. So I take it the regen braking only starts when your foot is totally off the accelerator? It just seems like when i am at a stop light, and i give it a small amount of pedal to move up a couple car length, that there is a strain, or force against my car. Like i said, maybe it is all in my head. And after all the comments, I just dont understand why anyone would not want to use regen braking. Just seems to be the most logical way to get the most out of your battery.

 

[Andy_STL]

Thank you for the replies. So I take it the regen braking only starts when your foot is totally off the accelerator? It just seems like when i am at a stop light, and i give it a small amount of pedal to move up a couple car length, that there is a strain, or force against my car. Like i said, maybe it is all in my head. And after all the comments, I just dont understand why anyone would not want to use regen braking. Just seems to be the most logical way to get the most out of your battery.

No, it can start even if you pull off the accelerator a little. Look right below your speed indicator. There is a very narrow line that will turn black to the right if you are using power to move the car and turn green to the left if you are putting power back into the battery through regen.

 

[rickdogg82]

No. you can be on power down a hill for example and regen will be in effect even though you are pressing the accelerator.

 

[ajdelange]

hmmmmm…looks like you went to a better school. lol

Anyone go to an even better school?

I guess so. Regen recovers not only kinetic energy but potential energy. This is how you are able to leave a location and arrive at your destination with the battery more charged than it was when you left. And why you can sometimes see a remaining range display of 999 miles.

 

[ajdelange]

That pedal is the accelerator/decelerator pedal. Push it towards the firewall and the car accelerates. Let it come back from the firewall and the car slows down. Deceleration is maximum when the pedal is at the rearmost limit of travel. Learn to "feather" the pedal to drive your car with minimum use of the friction brakes.

 

[ZOMGVTEK]

The only time you wouldn't want to use regen, is with very poor traction conditions like ice and loose surfaces where the vehicle can get unstable from the braking. Some people don't like to have to hold the throttle to keep the car going and prefer to roll.

It saves some energy, but generally its going to be a few percent more range for city driving. Obviously this depends on how much you accelerate and immediately stop, but its not THAT big of a deal in the energy recapture for regular driving. It's basically free energy and reduces brake wear though, so why not. I think it makes it easier to drive as well. Best guess is you get something like 60% of the energy you used to accelerate back into the pack. This can be a fair bit lower with a cold battery and higher regen power. But it really cuts down the penalty from starting and stopping frequently.

 

[Puddles]

The only time you wouldn't want to use regen, is with very poor traction conditions like ice and loose surfaces where the vehicle can get unstable from the braking. Some people don't like to have to hold the throttle to keep the car going and prefer to roll.

This is an interesting issue, and I do recall it being beaten to death before, but for the life of me I can't recall the final determination.

My assumption would be that the traction control system should be equally effective during periods of positive AND negative acceleration, and that going into an icy corner hot and dumping the throttle should not unsettle the car any more than going into an icy corner hot and tromping on it.

I have not yet encountered an icy corner, but if I do I will be sure to investigate. Repeatedly, for science sake, unless I end up in a ditch.

 

[ZOMGVTEK]

This is an interesting issue, and I do recall it being beaten to death before, but for the life of me I can't recall the final determination.

My assumption would be that the traction control system should be equally effective during periods of positive AND negative acceleration, and that going into an icy corner hot and dumping the throttle should not unsettle the car any more than going into an icy corner hot and tromping on it.

I have not yet encountered an icy corner, but if I do I will be sure to investigate. Repeatedly, for science sake, unless I end up in a ditch.

The traction/stability system is more or less just as functional in regen as it is acceleration. This doesn’t really matter, if you have very low physical grip, the rapid deceleration is likely to cause enough movement in one corner the car will be quite unhappy and potentially spin or slide. There’s just so little the car can do when the tires have remarkably low control over the car. On snow, you can hammer the throttle around a corner and it’s totally stable. In fact, it tends to be more stable if you hammer the throttle than if you lightly press it, at least with the dual motor. A touch of throttle ends up in 100% rear power, and that axle just lights up the tires almost immediately. It catches itself fast, but if you’re cornering near the limit as is you’re in bad shape. Regen basically has a similar effect, so you need quite a steady foot for limit driving on very slick surfaces. If you’re driving slow enough that the tires have considerable available overhead, this should be quite manageable.

If you encounter an icy corner with the stock tires, you’re most likely going to end up in a ditch. I have studded snows on now though, so my future data collection is going to be a touch skewed. I didn’t read any threads on this, but I was very surprised how happy the car was to kick the rear out at any whiff of throttle. I think the dynamics are quite good, but for the average unsuspecting person buying an ‘AWD’ car, it’s borderline dangerous. On snow you should have enough grip the car is moderately stable even in a slight slide. But on ultra slick stuff you’re gonna slide or spin and the car can’t stop it. For the enthusiast this isn’t really a problem though.