Chevy Bolt EV Forum banner

61 - 71 of 71 Posts

·
Registered
Joined
·
4,801 Posts
I used an online calculator to compare the Wh of energy stored in a mass of 3,800 pounds (Bolt, me, spare tire) at 70 mph, and 10 mph....234.43 Wh vs 4.7842 Wh...or 49 times the energy.
Yeah... I guess what I'm really wondering is how much power the motor can generate at, say,10MPH vs 70MPH. It obviously couldn't generate power for very long at 10MPH compared to 70MPH, but if it could generate even a tenth the power level it would lead to a much higher deceleration.
 

·
Registered
Joined
·
102 Posts
Discussion Starter #62
Are you saying that your friction brakes come on without using the brake pedal in D? I have never had that happen.
No, I'm not saying that. I'm saying I would have to be careful not to press the brake pedal hard enough to engage the friction brakes. And the only way I would know I'm not engaging the friction brakes is if regen is kept below 55 kw as displayed on the DIC. Or as Sean Nelson suggests, I could try to do it by "feel", i.e. only press the brake pedal hard enough to feel as if it were in L mode and my foot were off the accelerator.
 

·
Registered
Joined
·
5,382 Posts
And the only way I would know I'm not engaging the friction brakes is if regen is kept below 55 kw as displayed on the DIC.
The best way to know if the friction brakes are engaged is to have Torque Pro, and look at the e-brake PID.
 

·
Registered
Joined
·
5,382 Posts
Yeah... I guess what I'm really wondering is how much power the motor can generate at, say,10MPH vs 70MPH. It obviously couldn't generate power for very long at 10MPH compared to 70MPH, but if it could generate even a tenth the power level it would lead to a much higher deceleration.
OK. The total energy available at 70 mph is .0.23443 kWh. You guys are talking about generating 55 kW. If you did that for an hour you would generate 55 kWh. There are 3600 seconds in an hour.

55 kWh/0.23443 kWh = 234.6
3600 seconds/234.6 = 15.34 seconds

So assuming you can get the motor to generate that power continuously, you could do it for just over 15 seconds.

At 10 mph you have 0.0047842 kWh.
55 kWh/0.0047842 = 11496.2
3600/11496.2 = 0.31 seconds

Even if it was possible to do, I don't think you would get more than a tiny chirp from the tires in that time. You aren't going to hit your head on the steering wheel. :)
 

·
Registered
Joined
·
503 Posts
Driving in D on the highway is more efficient than driving in L if you never use the brakes.

When driving on a completely flat road at a constant speed, D efficiency is the same as L because power consumption and losses are the same to move the car forward. No brakes.

The frictional and standard energy losses (like the radio and heat) are the same in D and L, so the difference is coasting vs. slowing down and regenerating whenever you go downhill.

Regenerating slows the car. Regen is not 100% efficient. Rumors are 80%, but only GM knows.
Accelerating uses more energy than staying at the same speed. Therefore no amount of accelerating and slowing will ever be as efficient as maintaining speed (just a data point).

Since frictional losses are the same, any coasting helps get you to your destination. Regen slows you down.

So now put yourself with CC set 70mph on the freeway in a hilly area. Every single downward hill in L is less efficient than in D because regen will slow you down and is less efficient than coasting.

If you put the car in N at the top of every hill, your speed would increase by the bottom. Since CC will regen less in D than L when going downhill, you actually gain more forward momentum down every hill or use less regen which has more losses than coasting.

We're talking tiny amounts probably, less than 1% difference.

Drive in what you want. It's not worth it. Typing this wasn't worth it for me.

Next is windows down vs. AC and windows up.
 

·
Registered
2019 Chevy Bolt LT, Cajun Red (w/o fast charge)
Joined
·
9 Posts
My aim in this matter is to always bring the shifter back to "D".

For example: When I leave the driveway it's in "D". When I get to about 100 ft of the corner stop, I switch to "L" and use the accelerator as the "brake" by slowly or completely letting off the accelerator peddle. If I am coming up to a stop using this method, and I'm getting closer to the actual stopping point and I want a little more "brake", I add in the regeneration paddle on the steering wheel. Upon continuing from the stop, I switch back into "D" and I'm ready for the next stopping or slowing event.

Now, if I'm in stop-and-go traffic I find "L" quite convenient rather than constantly going from gas to brake and back.
On an Interstate I usually have it in CC and "D". Conversely....If I'm on a road with frequent up and down "steepish"grades with CC on, I prefer "L" because it seems to help the speed stay more constant.

It feels as though if I use "L" and CC on the interstate, the car does not coast/regen (for lack of a better way to describe it) as freely. It is the same feel if I have the CC off and in "L" while manually working the accelerator. There is a kind of "holding back" feel.....until I switch to "D" and that "holding back" feel goes away.
I use CC as frequently as possible as well because it seems to "know" better than I will just how much acceleration to put into the task at hand. (The "Green Ring" stays greener in CC.)

As a result, my mi/Kwh are high, my brakes are hardly worn (wheels nice and clean), and the "technique" scale reads in the higher ranges.
 

·
Registered
Joined
·
4,801 Posts
My aim in this matter is to always bring the shifter back to "D".

For example: When I leave the driveway it's in "D". When I get to about 100 ft of the corner stop, I switch to "L" and use the accelerator as the "brake" by slowly or completely letting off the accelerator peddle. If I am coming up to a stop using this method, and I'm getting closer to the actual stopping point and I want a little more "brake", I add in the regeneration paddle on the steering wheel. Upon continuing from the stop, I switch back into "D" and I'm ready for the next stopping or slowing event.
Sounds like a lot of work. I just leave the shifter in "L" and my foot autonomously transmits my desires to the car without me having to think about it.
 

·
Registered
Joined
·
131 Posts
I always drive in L because I'm used to it and if I'm accidentally in D, I'll suddenly need to brake unexpectedly because I'm not getting slowed by the regen.
I think I have better efficiency without the cruise control, probably because I slow down a few mph going up steep hills rather than try to maintain the speed limit.
 

·
Registered
Joined
·
32 Posts
How is that any different than any other form of braking or deceleration? If they rear end you, that's their fault. The brake lights will come on under regenerative braking, so if they hit you, they were following too close for the speed and not paying attention.
Well yes, it would be their fault. However having been rear ended twice (not in the Bolt) I have found the experience to be not hassle free so I prefer to avoid it. ;)
 

·
Registered
Joined
·
3,304 Posts
Well yes, it would be their fault. However having been rear ended twice (not in the Bolt) I have found the experience to be not hassle free so I prefer to avoid it. ;)
I agree. It's best to be a defensive driver, but ultimately, you cannot control the person behind you.
 

·
Registered
Joined
·
4,801 Posts
I agree. It's best to be a defensive driver, but ultimately, you cannot control the person behind you.
My driving education included tje tidbit: 'Danger ahead means danger behind'. In other words, a sudden stop means you might get rear ended. So I allow plenty of stopping distance in front, and when stopped I keep an eye out for people coming up to me and flash my brake lights if it looks dicey. This is something I've always done since long before I owned my Bolt.
 
61 - 71 of 71 Posts
Top