Driving in low

[SpaceMan]

I heard recetly from a volt driver that since there are no gears, driving around in "Low" is simply setting a different regenerative charging point in the accelerator- this driving in low makes a more efficient driving experience.
So, I tried it. And let me say, I can't go back.
The accelerator now does what I would want from an EV by smoothly braking to a stop without the brake pads. I even noticed that this deceleration effect turns on the brake lights (until you are stopped- then you still need the brake pedal). After a day of this, I found that on the highway "D" is still preferred so you don't have the quick deceleration but I will be in "L" the rest of my time driving.
So: does anyone know if driving the bolt around in low has any positive or negative effects on the car?

 

[SpaceMan]

And of course, I posted this in the wrong section... sorry everyone. I will try to move this to a more appropriate topic

 

[Zoomit]

So: does anyone know if driving the bolt around in low has any positive or negative effects on the car?

I think it's fair to say that depending on your driving style and routes, one mode may yield slightly more efficiency than another, but which mode you use really comes done to personal preference. I prefer and use L mode in my Spark EV all the time.

 

[LeftieBiker]

If you're looking for efficiency and range, it's better to drive in the mode that allows the most coasting, as Regen is only at best 40% efficient in recovering energy. Coasting, though, is pretty close to 90% efficient. If you want the one pedal driving experience, though, then "L" is the way to go. Just remember that using it in hot weather will heat the pack.

 

[summit]

Keep in mind that you have total control of level of regen up to the max, by not letting up the go pedal all the way. I use the regen-on-demand paddle on the steering for additional regen/slowing down in L. By minimizing brake usage, i think it's most efficient.

 

[boltage]

Keep in mind that you have total control of level of regen up to the max, by not letting up the go pedal all the way. I use the regen-on-demand paddle on the steering for additional regen/slowing down in L. By minimizing brake usage, i think it's most efficient.

From what I understand, using the brake pedal does regeneration unless you press it hard enough to indicate that you want to brake more than regenerative braking can slow the car. So you can do the same regenerative braking management with the brake pedal as you can with the button behind the steering wheel. The button can be useful if you want to prevent the car from creeping if you let go of the brake pedal.

Regarding coasting, seems like (in either D or L), you just have to find the accelerator pedal setting where the display shows neither use nor regeneration of electricity if you want to coast without additionally slowing the car through regeneration.

Essentially, the accelerator pedal controls a setting ranging from some regeneration (slowing) to full power acceleration. Relative to using D, using L changes the lower end of the range to a greater level of regeneration (greater slowing). It does not seem like L would be inherently more efficient, but it may help drivers used to late braking to train themselves to anticipate stops and slowdowns (which will help improve efficiency in any car).

 

[LeftieBiker]

Leaf drivers can coast by shifting into Reverse at speed. It isn't as bad as it sounds (there is no reverse gear and all "shifting" is done electronically, with lockouts) and it does give you full coasting. However, it also locks out Regen, and it isn't the safest way to drive. I'll be surprised if the Bolt doesn't also allow 'Neutral coasting'.

 

[SeanNelson]

Leaf drivers can coast by shifting into Reverse at speed.

Can't you just coast in "N" on the Leaf? I thought all cars were required to have an "N" position on the shifter which could be used in the event of an engine runaway.

 

[EldRick]

It would be appropriate to start calling it "L" mode, as it is not a low gear in any way.

 

[boltage]

So: does anyone know if driving the bolt around in low has any positive or negative effects on the car?

In theory, you can drive with the same efficiency (or inefficiency) in L as in D, and vice-versa.

Conside the chart below:

                  regen button behind wheel     coasting
                             |                      |
          | friction braking | regenerative braking | acceleration |
          |                  |                      |              |
D mode    |<----------brake pedal----------->*<----accelerator---->|
          |                  |                      |              |
L mode    |<----brake pedal----->*<---------accelerator----------->|
          |                  |                      |              |

* = neither brake pedal nor accelerator depressed

The chart shows the ranges of control over deceleration (left of the "coasting" line) and acceleration (right of the "coasting" line) one can get with the brake pedal and accelerator. I am assuming that the regeneration button behind the steering wheel gives the maximum regenerative braking before going to friction braking. "Coasting" would be like putting the car in neutral, but a safer way to do that is pressing the accelerator just enough that the energy use gauge shows neither energy consumption nor regeneration.

Compared to D mode, L mode gives the accelerator a wider range of control over deceleration and acceleration, but less fine resolution. The brake pedal consequently has a reduced range of control over deceleration. You could drive with identical acceleration and deceleration in D mode and L mode, but your pedal inputs would be different.

Of course, whether you would actually drive with the same efficiency in both modes depends on your driving habits. Highest efficiency would mean minimizing the use of friction braking. It would also mean minimizing the use of the heater (use the heated seats instead).

 

[Pigwich]

So: does anyone know if driving the bolt around in low has any positive or negative effects on the car?

You MIGHT in theory chew through front tires a little faster? As far as I can tell, pretty much all of the braking that happens in normal driving is happening with regeneration, so that means 100% front tires until either you stomp on the brakes, when the hydraulic brakes kick in on front and rear, or for that last MPH when you come to a stop and are applying the brakes to sit at a light or whatever.... so my theory is, no. For all practical purposes, it has no effect on the car, although my wife hates when I drive in traffic with L because she says it makes her car sick because of the constant speed adjusting you can do without lifting your foot. My kids know no different - I never drove my Spark EV in anything but L and it's fine.

 

[LeftieBiker]

In really hot weather (90+F) driving in L aggressively might tax the thermal management system, causing the pack to get hot. In that respect it's a little like driving an ICE in 2nd gear.

 

[CGameProgrammer]

No it's not; don't spread misinformation. L mode is simply one-pedal mode. Acceleration and top speed are exactly the same in it as they are in D or Sport mode.

Someone asked about neutral. It is a true coast with no regeneration at all, not even if you press the brake pedal. Motors and generators are disconnected from the wheels.

 

[LeftieBiker]

No it's not; don't spread misinformation. L mode is simply one-pedal mode. Acceleration and top speed are exactly the same in it as they are in D or Sport mode.

That's why I wrote "it's a little like driving an ICE in 2nd gear." I've been driving an EV with B mode for almost four years now, and it's a common comparison.

 

[drdiesel1]

^^^^ Nope! Not like driving an ICE in 2nd. The EV has no gearing change. It would only seem that way on regen.
It's a total inaccurate comparison. I can regulate my regen by using L Mode with finer modulation than using any other mode.

The regen paddle on the steering wheel is horrible because it's a preset amount with no way to regulate it unless you pulse it.
That's totally uncomfortable because it's on/off abruptly. I hate that paddle and never use unless I need to stop quicker than L Mode
will allow.
L Mode gives you 100% modulation and that includes ZERO (coast mode) regen without trying to pulse the stupid paddle.
Using the paddle would cause regen conditioning way before using L Mode would, IMO!

 

[user 124]

In really hot weather (90+F) driving in L aggressively might tax the thermal management system, causing the pack to get hot. In that respect it's a little like driving an ICE in 2nd gear.

Doesn't this car have a thermal battery management system that:
1) provides cooling vial liquid circulation and a radiator to limit heating of the battery cells;
2) limit charging at high temperatures?

In any case, If it can charge at 50+ kW for 30+ minutes without cooking the battery, then it can handle brief periods of regenerative charging.

 

[drdiesel1]

^^^^^^^ The Bolt is setup with a coolant system to control HVB temps. The cells are attached to a heat sink and
has no coolant flowing through the batteries like the Volt. It uses a Heater and a Chiller to maintain temps.
The Chiller is tapped into the A/C system and the heater uses HVB power when needed. The system does not
use a radiator to control HVB temps. Here's an image of the components used. :mrgreen:

 

[LeftieBiker]

It should be noted that I didn't claim that there isn't a thermal management system for the pack, or that there is any "gearing change" in L. Now how many of you guys have been driving/riding EVs with aggressive Regen for 15 years..? Regardless of what is actually happening in the powertrain, deceleration in that kind of mode feels, to the driver/rider, very much like backing off the throttle of an ICE vehicle in a low gear. I'm guessing that we all understand this, but for some reason some of us just want to argue for the sake of disagreeing. ;-)

I should have written that pack heating could be an issue in sustained aggressive driving, in hot weather. Not a Red Alert kind of issue, just the kind of thing you might want to avoid doing if you plan to keep the car for many years. The lack of a radiator in GM's TMS makes me a little less confident of its ability to handle extremely hot conditions, not more.

 

[CGameProgrammer]

I seriously doubt GM would ever allow the battery temperatures to exceed allowed specifications. Instead, the thermal management system is either robust enough to handle any driving style or battery draw would be reduced as necessary to keep temperatures low. But more than likely it's simply more than adequate.

Keep in mind that the larger the battery pack is, the less load it's under in all conditions. 150 kW is 2.5C for a 60-kW-h battery pack, but it would be 5C for the ~30-kW-h pack seen on other EVs.

 

[GetOffYourGas]

Leaf drivers can coast by shifting into Reverse at speed.

Can't you just coast in "N" on the Leaf? I thought all cars were required to have an "N" position on the shifter which could be used in the event of an engine runaway.

That's exactly what this does. When you try to shift a Leaf into "R" at speeds over 7MPH, the car goes to "N" instead. The "traditional" way of getting into "N" involves holding the shift puck to the left for about 3 seconds until the car beeps. This is just a shortcut to immediately shift to "N"