Chevy Bolt EV Forum banner

21 - 40 of 44 Posts

·
Registered
Joined
·
3,603 Posts
This reignites previous arguments.
One more time, the Bolt isn’t a Prius. In a Bolt in L, one can drive for weeks without ever needing friction braking. Slowing to a stop is done completely with regeneration.
... and you're still entirely wrong. No physics professor in the world would teach that expending energy and recovering some of it is more efficient than not expending it in the first place. We're talking about an amount so insignificant as to not bother, but since you insist on being wrong...
 

·
Registered
Joined
·
722 Posts
Please KEEP to the Original topic.
You all are getting way off topic to the questions asked by the OP.

I think that if you want more Regen use the Paddle on the wheel, then use brakes for a bit more and harder brakes for friction.
But again, if you are looking to Gain more back to the battery, it is not worth it for the pence you get.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #23
Thank you ALL for response.
I will try to address all of the comments below. Might a lengthy one...
To make it easier, I will not be calling names (code: /mention), I will simply comment on the statement.


First let me say this - from physics (regardless of ICE or EV stand point of view) coasting is the best energy use. And I mean true coasting - no energy is being taken back, no regen whatsoever. Therefore, my point was - would pressing brake pedal work towards regen as well or it is friction only, or maybe a blend of these two.
Focusing shortly on the energy.
For those nonbelievers. Example from FIAT. It has onboard charger of 6.6 kW. When charging at full power (battery is already conditioned, at +70 F) it will take about 17 A while being at 370 V (that is 6.29 kW). EVSE provides 6.94 kW according to ChargePoint App and my meter that is connected to the EVSE. That means that efficiency of charging is about 90% (6.29/6.94=0.90). The remaining 10%, that is 700 W is being wasted as heat.
The very same thing happens with regen braking, except that is has a larger effect because you must take motion loses (gearing, efficiency of the motor in regen). Hence, overall you can easily drop 20% from the total energy flow.
Take it to the next step.
To get the car moving you need, just lets assume for easier math, 10 kWh. I know, it is crazy high number, but only to get the idea through. To slow it down you will get back 6-7 kWh. Assumption of no air drag and rolling resistance.
The first 10% is lost in the converter DC/AC and the motor. And believe me - 10% is tiny amount.
Then, you want to recoup it - all regen (at least 10% on the motor and 10% on the battery itself - reversing chemistry of discharge is not easy to do).
So far we had 30% lost. And that is with my very generous estimate.

Let it slide (coast) you do not loose the 20% (at least) during regen.

I hope it makes sense now.


Very quickly for ICE.
This idea of BSFC (Brake Specific Fuel Consumption) - it is a map that shows when the engine is the most efficient. Turns out that almost all of them are the best between 1500 and 3000 rpm under WOT (wide open throttle). What it means - you hold your gear and push the pedal to the floor. Do it each gear until you reach your speed. Then, as it was said - do a wave or pulse. Means, in the tallest gear WOT until say 3000 rpm and let it coast until engine speed drops to 2000. Of course it cannot be done in AT with torque converter unlocked. Dual clutch could do it, yet the best is MT.
Digression...


As for L vs D.
Since I cannot get Bolt for a test drive here to actually feel it, I need to relay on you guys.
I am not sure I would like to engage regen all the time. I'd rather coast. In many cases I can see from distance that the lights just turned red, so I know I will need to stop eventually. But instead of keeping the speed and somehow gauge when I need to let off to engage regen, I want to coast and apply brake (read - regen) to come to a stop if needed.

Hence I wanted to know how much of friction is actually applied during regular driving in D vs L.
Are there any numbers to support statements?


I cooperate with ScanGauge manufacturer (Linear Logic from AZ).
Since I got SCII from them back in 2009 I have been testing it for X-Gauges on many cars. 500e is one of them. It will provide me real time info as voltage of the battery (HV), current, temp, heat/cool loops, and dozens of others. Hence I can see when regen works when friction is applied by simply comparing numbers or see if the number gets larger by depressing the brake more.
I do not expect such data here, but at least some info.

I know that it might seem like splitting hairs...


Finally.
Temperature aspect.
I did not see anyone to say anything about cold days.
Will regenerative braking work the moment you start driving? Of course I can expect it to be less powerful than on a warm day, but it still should work.
Right? Please any cold climate experience?
 

·
Registered
Joined
·
70 Posts
I personally have started using a blend of all 3 regen. I started out with 100% L but now, it f the traffic is moving steadily say on the highway, I drive in D until traffic starts to slow, then I “downshift” to L. When it picks up again, back to D. Makes me feel like I’m driving a Formula One car! Lol!

I find this method gives a smoother ride experience for me and my miles/kw has improved because I’m not constantly using battery to get back up to speed again.

“A body in motion tends to stay in motion.”
-Sir I. Newton
 

·
Registered
Joined
·
70 Posts
Thank you ALL for response.
I will try to address all of the comments below. Might a lengthy one...
To make it easier, I will not be calling names (code: /mention), I will simply comment on the statement.


First let me say this - from physics (regardless of ICE or EV stand point of view) coasting is the best energy use. And I mean true coasting - no energy is being taken back, no regen whatsoever. Therefore, my point was - would pressing brake pedal work towards regen as well or it is friction only, or maybe a blend of these two.
Focusing shortly on the energy.
For those nonbelievers. Example from FIAT. It has onboard charger of 6.6 kW. When charging at full power (battery is already conditioned, at +70 F) it will take about 17 A while being at 370 V (that is 6.29 kW). EVSE provides 6.94 kW according to ChargePoint App and my meter that is connected to the EVSE. That means that efficiency of charging is about 90% (6.29/6.94=0.90). The remaining 10%, that is 700 W is being wasted as heat.
The very same thing happens with regen braking, except that is has a larger effect because you must take motion loses (gearing, efficiency of the motor in regen). Hence, overall you can easily drop 20% from the total energy flow.
Take it to the next step.
To get the car moving you need, just lets assume for easier math, 10 kWh. I know, it is crazy high number, but only to get the idea through. To slow it down you will get back 6-7 kWh. Assumption of no air drag and rolling resistance.
The first 10% is lost in the converter DC/AC and the motor. And believe me - 10% is tiny amount.
Then, you want to recoup it - all regen (at least 10% on the motor and 10% on the battery itself - reversing chemistry of discharge is not easy to do).
So far we had 30% lost. And that is with my very generous estimate.

Let it slide (coast) you do not loose the 20% (at least) during regen.

I hope it makes sense now.


Very quickly for ICE.
This idea of BSFC (Brake Specific Fuel Consumption) - it is a map that shows when the engine is the most efficient. Turns out that almost all of them are the best between 1500 and 3000 rpm under WOT (wide open throttle). What it means - you hold your gear and push the pedal to the floor. Do it each gear until you reach your speed. Then, as it was said - do a wave or pulse. Means, in the tallest gear WOT until say 3000 rpm and let it coast until engine speed drops to 2000. Of course it cannot be done in AT with torque converter unlocked. Dual clutch could do it, yet the best is MT.
Digression...


As for L vs D.
Since I cannot get Bolt for a test drive here to actually feel it, I need to relay on you guys.
I am not sure I would like to engage regen all the time. I'd rather coast. In many cases I can see from distance that the lights just turned red, so I know I will need to stop eventually. But instead of keeping the speed and somehow gauge when I need to let off to engage regen, I want to coast and apply brake (read - regen) to come to a stop if needed.

Hence I wanted to know how much of friction is actually applied during regular driving in D vs L.
Are there any numbers to support statements?


I cooperate with ScanGauge manufacturer (Linear Logic from AZ).
Since I got SCII from them back in 2009 I have been testing it for X-Gauges on many cars. 500e is one of them. It will provide me real time info as voltage of the battery (HV), current, temp, heat/cool loops, and dozens of others. Hence I can see when regen works when friction is applied by simply comparing numbers or see if the number gets larger by depressing the brake more.
I do not expect such data here, but at least some info.

I know that it might seem like splitting hairs...


Finally.
Temperature aspect.
I did not see anyone to say anything about cold days.
Will regenerative braking work the moment you start driving? Of course I can expect it to be less powerful than on a warm day, but it still should work.
Right? Please any cold climate experience?
For what it’s worth, I sold my 2015 Fiat 500e to but the 2017 Bolt. Here’s why:

1) I needed more range..:a lot more range!

2) I was tired of being L2 charged to death so I needed DCFC.

3) I wanted 4 doors instead of 2

4) I waned more regen choices. With the Fiat, you only get one.

I still averaged 4 miles/kW in my Fiat 500e even after 75k miles AND the Bolt is a lot faster!
 

·
Registered
Joined
·
1,044 Posts
As for L vs D.
Since I cannot get Bolt for a test drive here to actually feel it, I need to relay on you guys.
I am not sure I would like to engage regen all the time. I'd rather coast. In many cases I can see from distance that the lights just turned red, so I know I will need to stop eventually. But instead of keeping the speed and somehow gauge when I need to let off to engage regen, I want to coast and apply brake (read - regen) to come to a stop if needed.


Finally.
Temperature aspect.
I did not see anyone to say anything about cold days.
Will regenerative braking work the moment you start driving? Of course I can expect it to be less powerful than on a warm day, but it still should work.
Right? Please any cold climate experience?
For the second question I am pretty sure that regen braking works even in cold days, it may be reduced but I have never seen it not work on a cold day. The only time it won't work is if you are charged to 100%, which I hardly do.

Even is D you will have regen engaged, no way around this. It is minimal, but still there. Please give L mode a shot. I was in the same boat as you in the beginning. I was trying to drive the Bolt like a ICE vehicle and didn't use L for the first 10,000 plus miles. I finally gave in and used L and I was upset at myself for not using it sooner. You can control the regen by the accelerator and it feels like you are coasting to a stop. A little bit of experience and you will be able to come to a stop exactly as you described, without having to touch the brake pedal at all. One pedal driving is simply amazing, efficient, makes your brake pads have almost an infinite lifespan, and is safer.

The safer part for me is great, especially on the highway. If you need to slow down quickly and you are in L mode, you immediately start to slow down quickly before you can get your foot on the brake pedal. Rear ending a car with a Bolt in L is much more difficult and is a great safety feature IMO. The only time I don't use L mode is when I have passengers that tend to get car sick. L mode seems to make their car sickness worse, especially if you are still learning to perfect the one pedal driving.

My advice to everyone is to try L mode for a week. This is how EV's should be driven!
 

·
Registered
Joined
·
3,603 Posts
This idea of BSFC (Brake Specific Fuel Consumption) - it is a map that shows when the engine is the most efficient. Turns out that almost all of them are the best between 1500 and 3000 rpm under WOT (wide open throttle). What it means - you hold your gear and push the pedal to the floor. Do it each gear until you reach your speed. Then, as it was said - do a wave or pulse. Means, in the tallest gear WOT until say 3000 rpm and let it coast until engine speed drops to 2000. Of course it cannot be done in AT with torque converter unlocked. Dual clutch could do it, yet the best is MT.
Just to clarify, most cars do not operate efficiently when the pedal is pressed to the floor or very near to it, especially since in an automatic transmission it will downshift. At WOT, the car will go open loop and revert to a rich fuel map rather than operating off the air/fuel ratio.

Here's an example map showing the sweet spot at 2,500 RPM and about 77% torque (engine load or throttle are related). Interestingly, due to the low RPM, it's only making 36% of peak power at this most efficient output. The engine is still capable of being fairly efficient as the RPMs go up assuming it stays at about 77% torque.

The most efficient way to operate an ICE in general is to give it 3/4 throttle up to 3,500 RPM, then shift and repeat until desired speed is reached.

 

·
Registered
Joined
·
328 Posts
I am not sure I would like to engage regen all the time. I'd rather coast. In many cases I can see from distance that the lights just turned red, so I know I will need to stop eventually. But instead of keeping the speed and somehow gauge when I need to let off to engage regen, I want to coast and apply brake (read - regen) to come to a stop if needed.
In L mode, you can coast, you just need to keep one eye on the DIC while driving and find the spot where there is no power consumption or regen. You'll be surprised at how quickly you can find and keep this spot with a little bit of practice in L mode.
 

·
Registered
Joined
·
1,323 Posts
In L mode, you can coast, you just need to keep one eye on the DIC while driving and find the spot where there is no power consumption or regen. You'll be surprised at how quickly you can find and keep this spot with a little bit of practice in L mode.
For true. There are some here who operate the go pedal as an on/off switch and it would be car-sick making to ride with them. However, most good drivers adapt easily to the beauty of infinite modulation speed control. My wife is a good driver, but no interest in the technical "why" of L-mode. It was just intuitively the logical method of operating a BEV and she uses it exclusively from Day One.

jack vines
 

·
Registered
Joined
·
118 Posts
Discussion Starter #30
For what it’s worth, I sold my 2015 Fiat 500e to but the 2017 Bolt. Here’s why:

1) I needed more range..:a lot more range!

2) I was tired of being L2 charged to death so I needed DCFC.

3) I wanted 4 doors instead of 2

4) I waned more regen choices. With the Fiat, you only get one.

I still averaged 4 miles/kW in my Fiat 500e even after 75k miles AND the Bolt is a lot faster!

Pretty much my mind now... although my orange 500e is cute and kind of a sleeper.
It is great for towing my little HarborFreight 4x8 trailer and is tiny enough to barely notice in a garage.
I am in a market for a small BEV. Smallest possible with 4-doors. Bolt seems to be the best option.

Do you recall how much charge would the 500e battery take? How was its degradation?
I am currently at 50 Ah what makes it about 19 kWh full capacity.
Funny thing is that it charges it "randomly" to 100%, meaning full is reached at 48 Ah, or another day - 49.5 Ah.


For the second question I am pretty sure that regen braking works even in cold days, it may be reduced but I have never seen it not work on a cold day. The only time it won't work is if you are charged to 100%, which I hardly do.
.........
The safer part for me is great, especially on the highway. If you need to slow down quickly and you are in L mode, you immediately start to slow down quickly before you can get your foot on the brake pedal. Rear ending a car with a Bolt in L is much more difficult and is a great safety feature IMO. The only time I don't use L mode is when I have passengers that tend to get car sick. L mode seems to make their car sickness worse, especially if you are still learning to perfect the one pedal driving.

My advice to everyone is to try L mode for a week. This is how EV's should be driven!
I will, for sure I will.


Just to clarify, most cars do not operate efficiently when the pedal is pressed to the floor or very near to it, especially since in an automatic transmission it will downshift. At WOT, the car will go open loop and revert to a rich fuel map rather than operating off the air/fuel ratio.

Here's an example map showing the sweet spot at 2,500 RPM and about 77% torque (engine load or throttle are related). Interestingly, due to the low RPM, it's only making 36% of peak power at this most efficient output. The engine is still capable of being fairly efficient as the RPMs go up assuming it stays at about 77% torque.
I wish those maps were readily available for ICE cars. Or at least torque/power graphs.
Something I got used to seeing in Poland, but never in the US when buying a car...

75% WOT - It is hard to gauge as throttle mapping is not always same. 2016 Fiat 500X (2.4 NA) could be 80% WOT at 40% pedal travel, while 2016 KIA Forte5 SX (1.6T) was about 30% at the same travel.

For true. There are some here who operate the go pedal as an on/off switch and it would be car-sick making to ride with them. H
This is what I am afraid of - it would feel like jerking back and forth.

In L mode, you can coast, you just need to keep one eye on the DIC while driving and find the spot where there is no power consumption or regen. You'll be surprised at how quickly you can find and keep this spot with a little bit of practice in L mode.
I might be just too afraid of it as it may seem like I can never let the foot to rest :)

I see there are two 2020 Bolts in Lansing, so I will give them a try.



How about brake lights? Do they illuminate when in L and decelerating?

It may seem like a hazard in certain situations...
 

·
Registered
Joined
·
328 Posts
I thought my foot would get tired as well, but I've taken many long highway drives of over an hour in L mode and I didn't even notice that my foot was pressing the pedal the entire time. Not a lot of force is needed to find the right spot; believe me, it is a great way to drive.

In L, brake lights illuminate above a certain deceleration threshold, but do not stay illuminated once stopped in L unless you put your foot on the brake pedal. This has been discussed A LOT elsewhere on this forum. I've developed the habit of pressing the brake pedal to turn on the brake lights if I see someone approaching behind me, but otherwise leave them off after I come to a stop.
 

·
Registered
Joined
·
3,603 Posts
75% WOT - It is hard to gauge as throttle mapping is not always same. 2016 Fiat 500X (2.4 NA) could be 80% WOT at 40% pedal travel, while 2016 KIA Forte5 SX (1.6T) was about 30% at the same travel.
I think our confusion is in the use of the term WOT. My interpretation is Wide Open Throttle, which means pedal mashed to the floor. Of course, with modern throttle-by-wire, the throttle could be wide open at lower pedal positions.

In my view, it's more useful to speak in terms of percent of available torque, or engine load.
 

·
Registered
Joined
·
118 Posts
Discussion Starter #33
In my view, it's more useful to speak in terms of percent of available torque, or engine load.
Good point.
According to TPS I never got 100% WOT, where WOT for me is throttle completely open allowing max air flow.
And despite belief that 100% WOT gives open loop - never had this happen. Open loop pops for a moment only to go to close loop and according to TPS throttle gets adjusted slightly.

But yes, I see your point. Speaking of load and % of torque is much better to understand.


When I said have the throttle completely opened - it was in relation to air flow and complete combustion in air. Any partial throttle produces less efficient combustion... more air=more fuel, but also more complete burning process.

We digressed too much :)
 

·
Registered
Joined
·
1,908 Posts
In L mode, you can coast, you just need to keep one eye on the DIC while driving and find the spot where there is no power consumption or regen. You'll be surprised at how quickly you can find and keep this spot with a little bit of practice in L mode.
Technically, you would want to see -0.5KW or -1.0KW. When it shows 0KW, that means it is recapturing energy to balance out the use from other components of the car.
 

·
Registered
Joined
·
4,545 Posts
I personally have started using a blend of all 3 regen. I started out with 100% L but now, it f the traffic is moving steadily say on the highway, I drive in D until traffic starts to slow, then I “downshift” to L. ... I find this method gives a smoother ride experience...
You can drive as smoothly as you like in "L" mode if you learn to be gentle with the accelerator pedal. I use "L" mode exclusively, and I find it to be even smoother than "D" mode because you never have to switch pedals between "go" to "stop". You can smoothly ramp from acceleration to deceleration or vice versa without any interruption, either rapidly or very, very gradually.

Indeed, you can even be in "L" mode and tape the regen paddle down so it's always engaged and still drive as smooth as silk. All the paddle does is to give you a wider range of deceleration choices, but you don't have to completely release the pedal to actually use them unless you need to.

When I'm in a hurry and I'm coming up to a corner I sometimes press the regen paddle before I start to decelerate - if I continue applying the same amount of accelerator pedal pressure nothing happens - I keep going the same speed. But then when I get to the point where I want to decelerate I carefully release pedal pressure to allow the braking force to smoothly ramp up and drop my speed down as much as I need to take the corner safely.

Folks who claim that "L" mode lacks smoothness simply haven't learned how to control the accelerator pedal. It's not the change from acceleration to deceleration that makes the ride seem abrupt, it's how quickly or gradually you allow the change to happen that counts. You can take as long as you want to go from 30mph to a stop in "L" mode if you release accelerator pedal pressure slowly. You can do it in seconds or literally take minutes, and you're never at a speed where you have to transition from the accelerator pedal to the brake pedal to continue the same rate of deceleration, be it strong or very very weak.
 

·
Registered
Joined
·
4,830 Posts
I do wish that the Paddle was able to press slowly. Now it is on or off and I do not like that. You can't Feather it like in L

I guess the fact that last night was New Years Eve is why two hours have past without anybody answering this. For more time than I like to admit, I wondered the same thing...until somebody on here pointed out that with the paddle depressed, you use the accelerator to modulate regen...exactly like in L.
 

·
Registered
Joined
·
328 Posts
Yes, exactly. The paddle basically gives you L mode "on demand" when in D.


I guess the fact that last night was New Years Eve is why two hours have past without anybody answering this. For more time than I like to admit, I wondered the same thing...until somebody on here pointed out that with the paddle depressed, you use the accelerator to modulate regen...exactly like in L.
 

·
Registered
Joined
·
50 Posts
Thanks, that would help a lot.

My point, basically is, to drive it like a regular car. Meaning, in D, take off foot - it will be decelerating with some regen. Then, if I must slow down faster, touch the brake pedal to let regen increase, but not use friction yet.

Not that I am after hypermiling, although I averaged 165 MPGe in my Fiat on summer, in city (Lansing area), but I want to make sure that the regen is activated from the brakes as well. Not like Tesla - one pedal driving only and brakes are friction.

Why?
Well, picture this. You loose about 10% of energy when accelerating. To charge, you loose another 10% (via EVSE). If you look on energy flow, to get up to speed and use on average 40 kW for a several seconds, you return maybe 25 kW (that is using regen only).
That is why I want it to coast and use the brake pedal to regen only when needed.
Hence, coasting is the most efficient way of driving it.

Oh, no I do not want to keep pulling the paddle on the steering wheel.
my impression is that the brake pedal only slows using the brake pads. it does not cause any regen.
if I drive in D, I do not detect any slowing when I life my foot from the 'gas pedal'. it coasts just like an ICE car. I can press the regen paddle on the steering wheel and get some regen.

I always drive in L and I add additional braking by pressing the regen paddle on the steering wheel. I rarely press the brake pedal although sometimes after stopping I rest my foot on it out of habit. I also drive almost always with cruise control on and I let the car manage maintaining a constant speed. I don't think I could do better. when I want to come out of cruise control I press the regen paddle although tapping the brake works also.
your milage may vary!
 

·
Registered
Joined
·
50 Posts
While we on the topic of regen...maybe some of the knowledgable folks here can comment on what I try to do.

I know that 'jack rabbit' starting uses more power than slower acceleration. But the opposite of that would be that rapid deceleration would produce more regen power than slowly coming to a halt. So I drive in L and try to maintain my speed as close as I can to where I have to stop and then take my foot off the 'gas' and press the regen paddle to slow down as fast as I can (and if I stop short, no big deal).

I'm wondering if this makes sense? thanks
 
21 - 40 of 44 Posts
Top