[LowOnCash]

I-Pace’s Changing Coasting and Braking Regen - Mike Mas

To help new I-Pace owners - More fully understand why the I-Pace brakes feel different at times, I thought a short article focusing on coasting and braking regen would be beneficial. Unlike a gas powered car, where the brake pedal always retains the same feel and braking response, the I-Pace’s braking abilities “at times” will change according to the lithium batteries charge.

Some I-Pace owners have trouble - Adapting to the I-Pace’s brakes. I have witnessed owners taking their car to a shop to change brake pads thinking there was brake problem when in fact, the brakes were working as designed. Even worse, I recall one owner selling his I-Pace, since he could not get used to the brakes.

The truth of the matter is - The I-Pace brakes will change its feel and response to pedal travel. This “feel” or changing brake response is the result of the fact the first 20-30% of brake pedal travel applies only “regen” braking, using the cars weight or kinetic energy as a power source to turn the electric motor as a generator, to both slow the car and develop regenerated power to recharge the battery. The remaining brake pedal travel uses the cars service (disk) brake. Therefore, the I-Pace has two separate braking systems; regen and disk brakes, working separate of each other but on the same pedal. However, at times when regen is not allowed, this initial brake pedal travel does not apply regen braking making the brake pedal feel somwhat non responsive.

Changing Brake Response - The reason the I-Pace brake pedal “at times” is changing response, is due to the simple fact the “battery control module” (BCM) does not allow braking nor even coasting regen to take place when the battery is at full charge or slightly below full charge. Therefore, at full charge, you’re only using the service disk brakes to stop the car. This means roughly for 25-50 miles after a full charge the brake pedal is constantly changing its feel and response. Each mile the charge declines, it increases regen slightly. the On my I-Pace, I do not achieve full regen braking until my range drops to around 185 miles. Therefore, from 220 to 185 miles, my braking regen will proportionally change and increase as the charge / range declines. This means the brake pedal is constantly changing it’s feel and response during this time. However, once the charge/range gets below 180 miles, the braking and coasting regen remain the same

Coasting Regen - Coasting regen which is accomplished by letting off the accelerator to achieve regen braking, operates on the same principles as the brake pedal regen. For this reason, the BCM also limits coasting regen as it does braking regen to prevent over-charging the lithium battery so at full charge the car easily coasts. For this reason, even if you select “high coasting regen” in the menu, if the battery is close to full charge, there is no coasting regen braking allowed.

Over-Charging - This cut-off and/or limiting of regen by the BCM occurs to protect the battery from over-charging. A typical example of why this is needed, lets say your home was located on top of a large hill or mountain. If you fully charged the battery overnight, then in the morning you jumped in the seat and headed down the mountain for a 20 -30 minute ride to the bottom using both coasting and braking regen to slow the car, this would severely over-charge the battery past its safety buffers which could damage the battery and or its health.

Battery Buffers - In brief, lithium batteries can easily last 15-20 years or more, provided they are charged and discharged properly. If you prevent fully charging and fully discharging a lithium pack, it improves its longevity and health. For this reason, most lithium batteries to include the I-Pace, use a low and high charge battery buffer. While Jaguar does not like to disclose much information of their batteries or system, most EV packs use a 5% upper and a 5% lower buffer to prevent the pack from ever being fully charged or discharged. With this in mind, getting back to the I-Pace’s brakes, this is why the BCM does not allowed regen at or near full charge since it will exceed this important safety buffer which assures the owner his pack will last the life of the car. Enjoy!

Stay Safe - Mike

 

[Deutsch100]

Great write up, Thank you. I personally love the brakes in my I-Pace....quiet, responsive and reliable (even if they feel a little strange sometimes Character!

 

[Pollo de muerte]

Thanks for the write up. I'm considering the I-Pace after years in a Chevy Volt. On the Volt, the regen brakes still operate with (mostly) the same pedal feel even at a high state of charge because the car will set the two traction motors against each other and gradually add in more regen as the SOC drops. It sounds like the I-Pace doesn't do this.

For short day-to-day commutes, can the I-Pace be configured to only charge up to 80% SOC (for example) to (a) help with battery maintenance and (b) keep the same brake feel?

Thanks again for the info.

 

[mojomike]

Thanks for the write up. I'm considering the I-Pace after years in a Chevy Volt. On the Volt, the regen brakes still operate with (mostly) the same pedal feel even at a high state of charge because the car will set the two traction motors against each other and gradually add in more regen as the SOC drops. It sounds like the I-Pace doesn't do this.

For short day-to-day commutes, can the I-Pace be configured to only charge up to 80% SOC (for example) to (a) help with battery maintenance and (b) keep the same brake feel?

Thanks again for the info.

I've found that the change in the brake feel only happens withing the first several miles of range when the battery is topped off. If you were to charge to 80% or even higher, perhaps 90 or 95%, there's no change in brake feel.

 

[Ken]

Thanks for the write up. I'm considering the I-Pace after years in a Chevy Volt. On the Volt, the regen brakes still operate with (mostly) the same pedal feel even at a high state of charge because the car will set the two traction motors against each other and gradually add in more regen as the SOC drops. It sounds like the I-Pace doesn't do this.

For short day-to-day commutes, can the I-Pace be configured to only charge up to 80% SOC (for example) to (a) help with battery maintenance and (b) keep the same brake feel?

Thanks again for the info.

Teslas work the same way as Mike beautifully described in the case of the I-Pace. At full charge there no regen and the regen doesn’t kick in until a certain % of charge has been used. It sounds like the Volt is a bit unusual in the BEV world.

For charging to a given %, unlike the Tesla where that can be done in the car’s menu, you’ll need to configure this on the charger end if the charger’s software will allow it. Knowing the hourly % charge rate, some chargers will allow you to schedule the necessary charging time to bring it to a given % of charge (you’ll have to make that time calculation). There is no communication that I’m aware of between the car & charger that tells the charger the exact % of charge the car is at.

If there’s an easier way to do this, I’m not aware of it, but would love to learn of it along with you.

 

[Ken]

On a very different, regen related topic, I read an interesting tidbit that had me thinking if anyone had tried this.

A reviewer had stated (can’t even recall if it was an I-Pace review) that for long highway driving, it was best to have regen set to low for maximum range as the result of improved coasting.

Has anyone heard of this or tried it? I can’t even recall this ever being discussed on the Tesla forum. Intuitively it makes some sense, but I’m wondering why I’ve never seen it discussed.

 

[Pollo de muerte]

As an old hypermiler (previously owned an OG 2000 Honda Insight), I much prefer as much coasting action as possible. Regen is nice, but it's basic physics that maintaining momentum is more efficient as opposed to trying to recapture electrons from the brake pedal.

I'll never like one-pedal driving mode for that reason and it's one of the negatives against Tesla IMO. Chevy's EV braking systems are better than any of the other EVs that I have driven. They're flexible (max regen paddle on the steering wheel and "L" driving mode for more regen or "D" for more coasting) and the blending of friction and regen braking is seamless.

 

[Pollo de muerte]

I've found that the change in the brake feel only happens withing the first several miles of range when the battery is topped off. If you were to charge to 80% or even higher, perhaps 90 or 95%, there's no change in brake feel.

That's what I was hoping to achieve with setting the car to charge to a lower SOC. Since my commute is only 15 miles round trip, I could just charge on the weekends unless I needed to drive out of town for a meeting.

 

[PS702]

That's what I was hoping to achieve with setting the car to charge to a lower SOC. Since my commute is only 15 miles round trip, I could just charge on the weekends unless I needed to drive out of town for a meeting.

The Wattcat app which is only for Android devices, allows you to set the SOC (see the bottom)

As far as one pedal driving, I am a purists when it comes to cars, but I fell in love with the one pedal.
It feels inefficient to use a break pedal at this point. It also preserves the breaks

 

[Ken]

I agree, once you get used to one pedal driving, it's hard to go back to traditional braking. But I guess I could see a rationale for long distance highway driving using low regen if it really gets you significantly more range. That's why I'd be curious to see a controlled test where we can see how much range you actually gain in that scenario.

I really wish there was something on iOS that performed the functions that WattCat does.

 

[DocHudson]

Thanks for the write up. I'm considering the I-Pace after years in a Chevy Volt. On the Volt, the regen brakes still operate with (mostly) the same pedal feel even at a high state of charge because the car will set the two traction motors against each other and gradually add in more regen as the SOC drops. It sounds like the I-Pace doesn't do this.

For short day-to-day commutes, can the I-Pace be configured to only charge up to 80% SOC (for example) to (a) help with battery maintenance and (b) keep the same brake feel?

Thanks again for the info.

I haven't tried it yet, but I saw a YouTube video that suggested setting your charging window under settings/preconditioning to a window that would equal whatever amount you want to add to the battery. He suggested a 32 amp (7 kW) charger would add about 9% per hour. He then set the charging window to be equal to whatever amount he wanted to add to the battery. I assume if you pull into the garage at 71% and set your charging window for one hour, it would stop charging at about 80%.

 

[LowOnCash]

Thanks for all the interesting replies guys - As user Mike suggested, by charging to 80%, it will avoid reduced Regen and add some additional health and longevity to the battery. Myself, since its only 25-30 miles round trip to town, I only charge the battery every 4-5 days, so I achieve full regen most of the time. Certainly, there is nothing wrong or dangerous when the I-Pace has reduced regen, they then operate as a normal Jag sedan.

After you own the I-Pace a month or so, you won't even know it’s changing response. It’s no different than coasting regen, where you control the accelerator pedal a bit different to control slowing the car. In most cases, 80-90% of all I-Pace braking can be achieved just using its regen, its a great system and the bonus is extra range!

To become more familiar how the battery charge affects the regen brakes, you can watch the regen bars on the cluster as you apply the brakes firmly, or during coasting regen. More and more bars will appear as the battery begins to discharge as you brake. Another method to physical feel when you achieve full regen, is to select high coating regen on your menu. When the battery reaches a certain point (188 mile on my car) the car will them begin a maximum rate of decent as you let off the accelerator. If you note the SOC and range at that time and you’ll have a guideline should you wish to only charge the car that amount, but it’s not really necessary.

I found there is two distinct advantages when achieving full coasting and braking regen, my favorite there is little to no brake dust on the wheels to clean, secondly you’ll extend the life of your brakes for as long as you own the car. While the service brakes on the I-Pace work well, they are surely not what you would find on other expensive EV or Hybrid sports sedans.

It's for this same reason of loss of regen braking at high SOC, that Porsche installs a set of 10 piston calipers on just the front wheels of the Taycan EV and a 8 piston set on Panamera Hybrid. Porsche bases their braking power and performance on the cars top speed (200+ mph) with "No Regen" assistance, so these cars offer exceptional braking power. In addition, if you frequent track events, Porsche and Mercedes also offers a ceramic brake options for a small extra charge of only $8-10,000. Ouch!

Stay Safe - Mike

 

[Scufflegrit]

The Wattcat app which is only for Android devices, allows you to set the SOC (see the bottom)

Does this work for anyone? In my experience WattCat may attempt to stop charging at the specified amount, but it doesn't succeed. From what I can tell, setting a charge window really only sets a charging start time, and it will only abide by that start time if it can fully charge the car before your departure time which you have to set or you can't delay your start time. It also doesn't stop charging at the end of your specified charge window. For instance, last week I set my departure for a couple days ahead, and set my charge window to 12:00 am to 6:00 am. What I think it should have done is charged from midnight to 6 am the first night then starting charging at midnight again the next night to finish off. Instead it ran from midnight to 9 am the first day. This is going to lead to a lot of gaming the departure times to achieve the desired charge window or SOC. It's needlessly complicated.

 

[mojomike]

I find that the Adaptive Cruise Control works so nicely on the highway that I use it instead of coasting and I keep the brakes set to high regen.

 

[LowOnCash]

I find that the Adaptive Cruise Control works so nicely on the highway that I use it instead of coasting and I keep the brakes set to high regen.

Thanks for the reply, however during hilly terrain or where there are numerous over-passes to climb, you'll achieve better mileage and range by “not using the speed control” during highway travel.

The problem is, the speed control maintains the same speed going up or down the hill. The problem occurs on the back side of a hill, the speed control will apply "braking regen" to slow the car.
While some might think this is efficient, it actually lowers your range since the regen it gained going down the hill, takes more power from the battery to replace to go back up the next hill. Even if there is not 2nd hill, the additional 10 mph of speed from coasting down the incline, helps to replace the energy used to climb the hill to save the battery.

While I don't recommend it, some owners will shift the transmission to neutral to coast down a hill for economy reasons. For the most part, high levels of coasting regen is more acceptable to city driving since it saves the service brake and regen furthers the range.

The use of coasting techniques can be a major advantage for saving fuel. For these reasons, both the Panamera hybrid and Taycan offer virtually no coasting regen, since free-coasting allows for improved range. On the Panamera hybrid, as it reaches the backside of a hill, the processor actually shuts down the gas engine and disconnects both the electric motor and engine, to allow free-coasting. If you’re not using the speed control, by pulling back on both paddles, it disconnects both the engine and the motor. Testimonial of how well this works, the Panamera hybrid weights 2.5 tons with 457 - 677 hp with speeds of 4.2-3.2 seconds @ 60 mph, yet still obtain 30+ mpg fuel range.

Stay Safe and enjoy your I-Pace - Mike

 

[Ken]

So Mike, based on what you said, I’m assuming you use low regen for long highway trips? I had asked this question earlier in this thread and was asking if anyone had done controlled highway tests with regen on high and then low.

I’m actually surprised BEV reviews don’t go into this discussion. I haven’t even seen it discussed on the Tesla forum.

 

[sciencegeek]

I’m actually surprised BEV reviews don’t go into this discussion. I haven’t even seen it discussed on the Tesla forum.

It's because the consumption difference between high and low regen is miniscule if you keep a steady foot and don't accel/decel all the time. Same driving style on high vs low regen will give you basically the same consumption, with differences that are too hard to measure given all the confounders. Remember, high vs low is just a remapping of parameters from the gas pedal to the brake pedal.

P.s.: According to JLR, on high regen setting, lifting foot off the gas pedal provides a maximum of 0.2g deceleration with recharging only. Pressing the brake gets you another 0.2g for a total of 0.4g until the friction brakes kick in.

 

[Ken]

It's because the consumption difference between high and low regen is miniscule if you keep a steady foot and don't accel/decel all the time. Same driving style on high vs low regen will give you basically the same consumption, with differences that are too hard to measure given all the confounders. Remember, high vs low is just a remapping of parameters from the gas pedal to the brake pedal.

P.s.: According to JLR, on high regen setting, lifting foot off the gas pedal provides a maximum of 0.2g deceleration with recharging only. Pressing the brake gets you another 0.2g for a total of 0.4g until the friction brakes kick in.

But now let's assume you're the guy that's determined to maximize his range and likes the idea of lots of coasting where appropriate. Would we now see a significant difference or would the difference still be not worth the effort? I can't see myself doing it because I think it takes the fun out of driving, but others may.

 

[sciencegeek]

Difference to what? If I'm that guy (which I'm not, haha) then I would drive gingerly on high or low regen, no matter what. If you're asking whether low regen causes you to change your driving behavior, that's another matter. But hypothetically if you drive exactly the same way along exactly the same route with exactly all the other consumers the same and the same stops and starts and everything the same .... you get my point ... then I doubt you'd see a difference between high and low regen setting.

 

[Ken]

Difference to what? If I'm that guy (which I'm not, haha) then I would drive gingerly on high or low regen, no matter what. If you're asking whether low regen causes you to change your driving behavior, that's another matter. But hypothetically if you drive exactly the same way along exactly the same route with exactly all the other consumers the same and the same stops and starts and everything the same .... you get my point ... then I doubt you'd see a difference between high and low regen setting.

Yup, that's what I meant, the difference between low & hi regen for highway driving. We need some controlled testing to take it out of the hypothetical realm. Should we put a call into Bjorn?