# "Welcome back "Regenerating Brakes limited"



## r-e-l (Dec 19, 2018)

Yes, its fall time but the temp didn't drop out that low (62) to start getting these warning again. the regenerating bar also looks "its usual" yet I am getting those warning ever since V10 came out (not all the time, but at times).

to compare … other folks in WA started noticing those?


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## Dr. J (Sep 1, 2017)

I thought "regenerating breaks" were what I got at the Supercharger.


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## scifi_tv_fan (Oct 24, 2016)

Been getting it pretty much every time during startup initialization. I have v10 installed.


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## Rick Steinwand (May 19, 2018)

Me too, but highs have been 50's and nights approaching freezing. I'm looking forward to summer.


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## JWardell (May 9, 2016)

Yep. Remember, regen starts limiting as soon as the battery drops below 75-80F...and being a large mass, the battery holds the cold overnight temperatures much longer than the air.


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## gary in NY (Dec 2, 2018)

Hardly touched the brakes since May. Good bye one pedal driving (for now).


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## DocScott (Mar 6, 2019)

r-e-l said:


> Yes, its fall time but the temp didn't drop out that low (62) to start getting these warning again. the regenerating bar also looks "its usual" yet I am getting those warning ever since V10 came out (not all the time, but at times).
> 
> to compare … other folks in WA started noticing those?


Got it in New York City northern suburbs today. Outside temperature was 64 F, but it had been cold the night before. The regen bar did show a bunch of dots, though.


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## Kizzy (Jul 25, 2016)

Time to start timing charging or preconditioning before leaving?


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## JasonF (Oct 26, 2018)

Kizzy said:


> Time to start timing charging or preconditioning before leaving?


The energy you spend on that will never be recovered via regen braking. Just let the battery warm up normally.


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## JWardell (May 9, 2016)

JasonF said:


> The energy you spend on that will never be recovered via regen braking. Just let the battery warm up normally.


Yes, but driving will be much more enjoyable when you heat up the battery enough to charge and regen. Many folks pre-charge the battery in the winter before leaving because of this. Put some value on happiness 
Actually, in the right situations, it can actually save energy, if your commute never gets fast enough to heat the battery much but has a lot of braking where regen would save a good amount of energy vs using friction brakes for the whole trip/long period before the battery warms up.


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## Rick Steinwand (May 19, 2018)

Lack of regen wears my brakes out sooner.


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## Feathermerchant (Sep 17, 2018)

Remember that using no regen (and the same amount of brakes) is the most efficient way to drive. Regen involves converting the kinetic energy of your vehicle into electricity thru the tires, gear box, motor and inverter then storing it in the battery then recovering it from the battery and thru the inverter, motor, gearbox and tires into kinetic energy. You only recover a percentage of the energy you started with. By coasting, you 'recover' all the kinetic energy. You do have to plan ahead while driving and you should not annoy other drivers but coasting will help reduce the loss in range during cold weather.


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## Kizzy (Jul 25, 2016)

Feathermerchant said:


> Remember that using no regen (and the same amount of brakes) is the most efficient way to drive. Regen involves converting the kinetic energy of your vehicle into electricity thru the tires, gear box, motor and inverter then storing it in the battery then recovering it from the battery and thru the inverter, motor, gearbox and tires into kinetic energy. You only recover a percentage of the energy you started with. By coasting, you 'recover' all the kinetic energy. You do have to plan ahead while driving and you should not annoy other drivers but coasting will help reduce the loss in range during cold weather.


While that is true, I do not plan to coast down the steep and curvy hills in my neighborhood. I still need to use my brakes even with full regen available.


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## Feathermerchant (Sep 17, 2018)

I'm not recommending you do anything unsafe.


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## JWardell (May 9, 2016)

Feathermerchant said:


> Remember that using no regen (and the same amount of brakes) is the most efficient way to drive. Regen involves converting the kinetic energy of your vehicle into electricity thru the tires, gear box, motor and inverter then storing it in the battery then recovering it from the battery and thru the inverter, motor, gearbox and tires into kinetic energy. You only recover a percentage of the energy you started with. By coasting, you 'recover' all the kinetic energy. You do have to plan ahead while driving and you should not annoy other drivers but coasting will help reduce the loss in range during cold weather.


Except that at some point you have to stop coasting around the place all free spirited and all, and come to a stop...


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## Feathermerchant (Sep 17, 2018)

Sure. I agree. I have been able to lower my Wh/mi from ~270 to 250 by carefully going easy on the regen.


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## Needsdecaf (Dec 27, 2018)

Feathermerchant said:


> Remember that using no regen (and the same amount of brakes) is the most efficient way to drive. Regen involves converting the kinetic energy of your vehicle into electricity thru the tires, gear box, motor and inverter then storing it in the battery then recovering it from the battery and thru the inverter, motor, gearbox and tires into kinetic energy. You only recover a percentage of the energy you started with. By coasting, you 'recover' all the kinetic energy. You do have to plan ahead while driving and you should not annoy other drivers but coasting will help reduce the loss in range during cold weather.


While what you say has some truth to it, saying you recover "all" the kinetic energy when coasting is also false. You are losing kinetic energy to friction in the drive system and air resistance as well.

I guess the best way to put it is

Most efficient - coasting, not having to slow at all. But this requires careful planning of your driving and often a sub-optimal driving experience. 
Somewhat efficient - using regen for 100% of your slowing. A decent (is it 67%?) percentage of your energy is put back into the battery to use later. 
Least efficient - using friction brakes. 100% of the energy is gone forever.


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## Feathermerchant (Sep 17, 2018)

I did not mention driving friction (tires, air, drivetrain) because those are lost in any case regardless of regen. 
Biasing your drive toward coasting does require learning a little but once learned, it is not at all difficult.


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## DocScott (Mar 6, 2019)

I also understand what you're saying, but I think there's a way to get sort of the result that matches better with people's intuition: rather than describing it as maximizing coasting, describe it as minimizing accelerations. If you're constantly slowing down and speeding up, you'll waste more energy. While it's _actually_ the case that the energy is lost during the slowing down process, you _see_ energy transferred out of the battery (via the various energy readouts) when you accelerate, and so it's easier to train yourself to keep those accelerations to a minimum. Of course, what that really means is coasting more!


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## Mr. Spacely (Feb 28, 2019)

Funny to hear you EV'ers try to remember how to coast and drive efficiently...


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## Needsdecaf (Dec 27, 2018)

Mr. Spacely said:


> Funny to hear you EV'ers try to remember how to coast and drive efficiently...


yeah, none of this stuff is EV specific for sure. It's best practices for driving no matter what. Just that it matters more on an EV.


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## Long Ranger (Jun 1, 2018)

Needsdecaf said:


> yeah, none of this stuff is EV specific for sure. It's best practices for driving no matter what.


Completely agree.


Needsdecaf said:


> Just that it matters more on an EV.


I actually think it matters less in most cases. I'll agree that it does matter more whenever you are on a road trip and trying to maximize the range of the vehicle.

However, for day to day driving, I think it matters less. Cars without regen are going to lose more energy when driving with a jerky start/stop technique than those with regen. Also, increases in efficiency actually matter more for less efficient vehicles. It saves a lot more money and energy if the least efficient vehicle on the road gets a 10% efficiency increase vs. a 10% increase for the most efficient vehicle.


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## DocScott (Mar 6, 2019)

Yeah--call it the "Prius effect." When the Prius first came out and it had that real-time screen that showed you the energy flows, a lot of people became much more conscious of what was efficient driving and what wasn't. In an ICE car from the period, your only feedback was the trip odometer when you went for a fill-up, so there wasn't any way to tell what specific maneuvers were efficient or inefficient. Nowadays, most ICE cars have a real-time estimate of mpg, but it still isn't nearly as responsive as in EVs. 

For BEVs, you've now got the range remaining shown in miles, which encourages the driver to be hyperaware of whether that estimated range is being met or not. So it takes the Prius effect one step further.


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## Needsdecaf (Dec 27, 2018)

DocScott said:


> Yeah--call it the "Prius effect." When the Prius first came out and it had that real-time screen that showed you the energy flows, a lot of people became much more conscious of what was efficient driving and what wasn't. In an ICE car from the period, your only feedback was the trip odometer when you went for a fill-up, so there wasn't any way to tell what specific maneuvers were efficient or inefficient. Nowadays, most ICE cars have a real-time estimate of mpg, but it still isn't nearly as responsive as in EVs.
> 
> For BEVs, you've now got the range remaining shown in miles, which encourages the driver to be hyperaware of whether that estimated range is being met or not. So it takes the Prius effect one step further.


BMW's and Mercedes of the 80's had a efficiency meter, which was essentially a vacuum gauge. They swung back and forth in real time response to your right foot. The Mercedes was not calibrated to any scale but the BMW was. It gave you a good idea of when you were stomping on it. I found the BMW to be pretty well judged

One note...man, I love how clear and legible those gauges are. Very useful info, and zero branding (see a logo on any of them??).

Here is an E30 BMW. Notice the dial in the lower section of the tach:










From the E Class of the late 80's.


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