Regen and front wheels

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EVMan

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Feb 25, 2017
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I read and understand , below 12 miles, the regen is not actual regn, but brake, as with low rotation or voltage , they cannot regen
When i drive my tesla, the chart is different, its not linear , as it does not use friction breaks.
The regen strength increase significantly by 20 miles and the car will coast suddenly after 5 miles or so


My question is , when i3 uses breaks automatically below 12miles , hopefully its using the front wheels more, for stability and better wheel mileage and wear.
Any thoughts ?
 
EVMan said:
I read and understand , below 12 miles, the regen is not actual regn, but brake, as with low rotation or voltage , they cannot regen
It is certainly true that regen braking power decreases as the rotational speed of the motor decreases such that regen braking power alone is almost certainly insufficient to bring a low rolling resistance i3 to a complete stop. However, there is another way that additional braking power could be implemented other than using friction brakes: the application of reverse electrical power to the motor.

The brake rotors on our i3 are rusty enough that I can easily hear when the friction brakes are applied. E.g., when driving in urban traffic under ACC, if the deceleration rate necessary to avoid colliding with a vehicle ahead cannot be attained by regen braking alone, friction braking is applied which is very apparent to me because of the scratchy friction braking sound. However, I never hear the friction brakes when decelerating to a stop using regen braking with ACC off, so I'm pretty confident that friction brakes aren't used to come to a complete stop under regen braking. That said, I haven't been able to find any official description of how i3 regen braking is implemented.

EVMan said:
My question is , when i3 uses breaks automatically below 12miles , hopefully its using the front wheels more, for stability and better wheel mileage and wear.
It's possible that to better mimic regen braking, friction braking could be applied only to the rear friction brakes when stopping using regen braking and that the rear rotors on our i3 aren't rusty enough to be heard. This seems unlikely, but anything's possible.
 
The car will use the friction brakes if the battery is full and regen could start to overcharge the batteries. In practice, I've only noticed it a few times in my 4+ years of driving mine. As noted, to me at least, it's fairly evident when the friction brakes are applied verses the regen slowing the vehicle. IMHO, BMW did a good job of mimicking regen with the brakes when required.
 
I believe that when the i3 braking system is calling for the application of friction brakes in addition to regen. (i.e. when gradually decelerating by partially lifting foot off the accelerator) it is so indicated by the performance display within the instrument cluster. When the indicator rotates to the far left and partially into the white zone, I believe the friction brakes are being applied. When one manually applies the friction brake, that power flow indicator rotates fully into the white zone. My experience with my 2014 BEV is that as others have said, one can hear the system application of friction brakes (either manually or automatically) and that the front brakes are applied in concert with the rear brakes.
 
Regarding the 'Regen Braking' , as I have mentioned , I believe there are 3 different windings in the Motor/Generator and that only 1 of those windings is used at higher speed 'Regen Braking' , 2 at medium speed , and all 3 only at slower speed . This gives the 'Regen Braking' a similar effective force at the different speed ranges . I'm going to guess that maybe , originally , all 3 phases were used at all speeds . That could explain the strong (maybe too strong) 'Regen Braking' force that was experienced at higher speeds before changes were made , via software , to dial back that amount . Here's a good question . What is the drive ratio from the Motor to the wheels and from the wheels to the generator , remembering that the ratio is inverted for the other function (motor-generator) .
 
While i never hear the breaks, but yes as jadnashuanh said, i observed , when battery is fully charged, the car looses regen at higher speeds but below 12 miles , it behaves much more normally. So i believe brakes are involved.

But since my rear ties only skid , when wet in my driveway , i guess its only rear tires.
i wish it was all the tires, when friction brakes.
 
CanisLupus said:
Regarding the 'Regen Braking' , as I have mentioned , I believe there are 3 different windings in the Motor/Generator and that only 1 of those windings is used at higher speed 'Regen Braking' , 2 at medium speed , and all 3 only at slower speed . This gives the 'Regen Braking' a similar effective force at the different speeds . I'm going to guess that maybe , originally , all 3 phases were used at all speeds . That could explain the strong (maybe too strong) 'Regen Braking' force that was experienced at higher speeds before changes were made , via software , to dial back that amount . Here's a good question . What is the drive ratio from the Motor to the wheels and from the wheels to the generator , remembering that the ratio is inverted for the other function (motor-generator) .

While the regen for i3 looks quite linear ( when battery not fully charged) , the tesla M3 is not linear.
It becomes very very strong around speed of 20 , and then zeros at creep speed , like gas cars at 3-4 miles
So yes , many things are going on. even the inverter might have their own limits and capabilities.
 
I own a Chrysler Pacifica which has brakes similar to Tesla. They are based on Bosch iBooster master cylinder https://www.youtube.com/watch?v=lJzbCA6qrBw&t=1s When the brake pedal is applied it will regenerate first and switch to the traditional brakes at low speed or when a strong braking is needed. I'm not sure if i3 has a similar system.
 
I'm thinking the front brakes are applied , that would make sense. I would like to test it out on the snowy day in an open parking lot and just release accelerator pedal and see what happens
 
Seasidenj said:
I'm thinking the front brakes are applied , that would make sense. I would like to test it out on the snowy day in an open parking lot and just release accelerator pedal and see what happens

It makes sense that front are applied, but on a wet slippery driveway , when i am taking a turn with zero accelerator , , my rear tire always skids.
 
Seasidenj said:
I'm thinking the front brakes are applied , that would make sense. I would like to test it out on the snowy day in an open parking lot and just release accelerator pedal and see what happens


It happened again. On a steep down slope , after a small bump, only the rear tiers skidded . So it looks like due to 'keep it simple' , the brakes are applied only in rear.
 
FWIW, going downhill, the weight transfer to the front during slowing means it is much harder for the front wheels to lock up versus the rears. Throw in the antilock logic, and things get a bit more complicated. Obviously, though, regen only applies to the driven wheels, the rear on an i3. Now, some Teslas have all wheel drive, so they can do regen on both axles. Don't know that they do, but they could.
 
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