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> "EVs often require a warm-up period before they can deliver maximum regen braking. Tesla gives the driver a warning when full regenerative braking is unavaila

> "EVs often require a warm-up period before they can deliver maximum regen braking. Tesla gives the driver a warning when full regenerative braking is unavailable. Chevrolet doesn’t do so. This can be alarming to the driver who lifts off the right pedal expecting significant deceleration and gets virtually none" Whoa, inconsistent brake feel? That's kind of terrifying. You'd think Chevy would calibrate the brake feel across states.

andrewtbham 10y ago
it's not brake feel... it's the feel off the accelerator. when you let of the accelerator in a Tesla, it doesn't coast, it's like letting of the trigger of an electric drill.. it quickly grinds to a halt. it's strange to get used to at first but you get the feel by the end of a test drive. it is strange to still be pressing the accelerator as you pull up behind a car at a red light. this weird feel is one of the problems that halted tesla's collaboration with toyota on electric rav4 drivetrains.
- birdmanjeremy 10y ago
  Do you have a source on the last part? The rav4 EV has an aggressive regen mode, it's just not the default state of the 'transmission'.
  - andrewtbham 10y ago
    http://insideevs.com/insight-toyota-tesla-partnership-marred-clashes-engineers/ http://insideevs.com/insight-toyota-tesla-partnership-marred... Toyota’s rejection of Tesla’s proprietary regenerative braking system, as it enabled the system upon release of the accelerator which Toyota felt was too abrupt and disconcerting for their customers. Any adjustment meant opening up and sharing either Tesla or Toyota’s “code” – of which neither was willing to do
    - birdmanjeremy 10y ago
      Thanks. That sucks, the Rav4 EV really is a great car. It's too bad it exists in such small numbers.
lallysingh 10y ago
These aren't brakes, this is the braking effect of the motors in generator mode. It's still a bad surprise, but you can tap the brakes if you want to slow down.
r00fus 10y ago
Does Toyota have a patent on this? I know my 2005 Prius even in pure EV mode has a consistent brake response... I believe it simply bleeds off the excess regen if batteries are already fully charged (ie, going downhill on a long slope).
- CarVac 10y ago
  My 2004 Prius (which should have the same behavior as your 2005) definitely doesn't have consistent brake response: the first inch or so of travel is completely electronic and when the battery is completely full (having gone down a long hill) it doesn't do any regeneration at all and neither letting off the accelerator nor using that first inch of brake travel does absolutely nothing. If you're in B mode, it will use compression braking (and if you're stopped, it'll bleed off energy by spinning the engine without any gas), but that doesn't change when you actually press on the brake pedal. I rented a 2009 Prius once, and was surprised by the brake pedal being completely electronic. When the battery was completely full, I noticed the brake pump noise occurring immediately upon touching the brake, instead of partway down the travel like it usually does when regeneration is working. My mom's Leaf also has a fully electronic pedal, but I've never driven it down a very long hill with a fully-charged battery, and there's no telltale brake pump noise, so I don't know if it changes its behavior with the battery filled to capacity.
  - aembleton 10y ago
    Interesting, I've noticed my 2008 model Prius effectively using 'B' mode when the battery is full and I'm heading down a hill even thought it is in 'D' mode. Maybe I just haven't noticed the change in brake feel or it is a UK specific feature.
- aembleton 10y ago
  The Prius can dump the energy into turning the engine over, just as a regular ICE would. You can hear this by starting at the top of a hill with a full battery and in `D` mode. Then, as you roll down it, you can hear a noise from the engine as it is being turned over as it uses the regen energy.
thebspatrol 10y ago
It's more of an engine-brake feel as you experience in a vehicle with a manual transmission. I doubt it's that alarming. When you let off the accelerator in a manual transmission vehicle, it's more of a "test the water" type of thing, and then you can change gear from there. It's not like people are going to rely on engine braking to come to an immediate stop.
sf_rob 10y ago
Side note: I wonder if they fixed the terribly noticeable transition between regen braking and mechanical braking that I experienced in a few rental Volts.
outworlder 10y ago
This is wrong. There's no warmup period. What there is is that, if the battery is completely full, the energy has nowhere to go. So the car does not use full regen. This could be mistaken for a "warmup". As another poster commented, this changes the accelerator feel, not the brakes.
- beefield 10y ago
  I admit being lazy here, but I wonder what kind of resistor (and what kind of cooling) it would be needed to dump the regen braking electrical energy there instead of battery? Probably impractical...
  - polar8 10y ago
    At that point the car would just us the brakes until regen was possible.
- bluehawk 10y ago
  I disagree completely. Sure, the change in feel is related to the accelerator, but it's the slowing down of the car that changes. In a gasoline car that would be referred to as "engine braking". Imagine if in your gas car, when the tank was full, it didn't engine brake. I can imagine people getting caught off guard when the car didn't slow down like they expect. Muscle memory is very important, and having the car behave unexpectedly is bad.
  - outworlder 10y ago
    For non-Tesla cars, the effect is really minimal. As in, noone expects to actually "break" at a stop light with the regen only. Yes, I have tried, even with the Leaf's "B" mode, which increases regen. I've heard that the Tesla's regen is so aggressive that it will even turn on the brake lights. In that case then, I agree.
- taneq 10y ago
  Surely they'd fit a braking resistor to cover this case? Most VSDs support them so I'd be amazed if it was too much trouble to use one with a car controller.
secabeen 10y ago
It only lasts about a few minutes/miles, but I agree, it would be nice for the behavior to be calibrated across states.

andrewtbham 10y ago

it's not brake feel... it's the feel off the accelerator. when you let of the accelerator in a Tesla, it doesn't coast, it's like letting of the trigger of an electric drill.. it quickly grinds to a halt. it's strange to get used to at first but you get the feel by the end of a test drive. it is strange to still be pressing the accelerator as you pull up behind a car at a red light. this weird feel is one of the problems that halted tesla's collaboration with toyota on electric rav4 drivetrains.

birdmanjeremy 10y ago
Do you have a source on the last part? The rav4 EV has an aggressive regen mode, it's just not the default state of the 'transmission'.
- andrewtbham 10y ago
  http://insideevs.com/insight-toyota-tesla-partnership-marred-clashes-engineers/ http://insideevs.com/insight-toyota-tesla-partnership-marred... Toyota’s rejection of Tesla’s proprietary regenerative braking system, as it enabled the system upon release of the accelerator which Toyota felt was too abrupt and disconcerting for their customers. Any adjustment meant opening up and sharing either Tesla or Toyota’s “code” – of which neither was willing to do
  - birdmanjeremy 10y ago
    Thanks. That sucks, the Rav4 EV really is a great car. It's too bad it exists in such small numbers.

lallysingh 10y ago

These aren't brakes, this is the braking effect of the motors in generator mode. It's still a bad surprise, but you can tap the brakes if you want to slow down.

r00fus 10y ago

Does Toyota have a patent on this? I know my 2005 Prius even in pure EV mode has a consistent brake response... I believe it simply bleeds off the excess regen if batteries are already fully charged (ie, going downhill on a long slope).

CarVac 10y ago
My 2004 Prius (which should have the same behavior as your 2005) definitely doesn't have consistent brake response: the first inch or so of travel is completely electronic and when the battery is completely full (having gone down a long hill) it doesn't do any regeneration at all and neither letting off the accelerator nor using that first inch of brake travel does absolutely nothing. If you're in B mode, it will use compression braking (and if you're stopped, it'll bleed off energy by spinning the engine without any gas), but that doesn't change when you actually press on the brake pedal. I rented a 2009 Prius once, and was surprised by the brake pedal being completely electronic. When the battery was completely full, I noticed the brake pump noise occurring immediately upon touching the brake, instead of partway down the travel like it usually does when regeneration is working. My mom's Leaf also has a fully electronic pedal, but I've never driven it down a very long hill with a fully-charged battery, and there's no telltale brake pump noise, so I don't know if it changes its behavior with the battery filled to capacity.
- aembleton 10y ago
  Interesting, I've noticed my 2008 model Prius effectively using 'B' mode when the battery is full and I'm heading down a hill even thought it is in 'D' mode. Maybe I just haven't noticed the change in brake feel or it is a UK specific feature.
aembleton 10y ago
The Prius can dump the energy into turning the engine over, just as a regular ICE would. You can hear this by starting at the top of a hill with a full battery and in `D` mode. Then, as you roll down it, you can hear a noise from the engine as it is being turned over as it uses the regen energy.

thebspatrol 10y ago

It's more of an engine-brake feel as you experience in a vehicle with a manual transmission. I doubt it's that alarming. When you let off the accelerator in a manual transmission vehicle, it's more of a "test the water" type of thing, and then you can change gear from there. It's not like people are going to rely on engine braking to come to an immediate stop.

sf_rob 10y ago

Side note: I wonder if they fixed the terribly noticeable transition between regen braking and mechanical braking that I experienced in a few rental Volts.

outworlder 10y ago

This is wrong. There's no warmup period. What there is is that, if the battery is completely full, the energy has nowhere to go. So the car does not use full regen. This could be mistaken for a "warmup". As another poster commented, this changes the accelerator feel, not the brakes.

beefield 10y ago
I admit being lazy here, but I wonder what kind of resistor (and what kind of cooling) it would be needed to dump the regen braking electrical energy there instead of battery? Probably impractical...
- polar8 10y ago
  At that point the car would just us the brakes until regen was possible.
bluehawk 10y ago
I disagree completely. Sure, the change in feel is related to the accelerator, but it's the slowing down of the car that changes. In a gasoline car that would be referred to as "engine braking". Imagine if in your gas car, when the tank was full, it didn't engine brake. I can imagine people getting caught off guard when the car didn't slow down like they expect. Muscle memory is very important, and having the car behave unexpectedly is bad.
- outworlder 10y ago
  For non-Tesla cars, the effect is really minimal. As in, noone expects to actually "break" at a stop light with the regen only. Yes, I have tried, even with the Leaf's "B" mode, which increases regen. I've heard that the Tesla's regen is so aggressive that it will even turn on the brake lights. In that case then, I agree.
taneq 10y ago
Surely they'd fit a braking resistor to cover this case? Most VSDs support them so I'd be amazed if it was too much trouble to use one with a car controller.

secabeen 10y ago

It only lasts about a few minutes/miles, but I agree, it would be nice for the behavior to be calibrated across states.