miles due to regeneration

[gpsman]

There are a few cases per month when I desire zero regen. Coasting on a 4% grade is a good example.

I find myself "shifting" to N in these cases.

About my only desire (beyond better seats!) would be a disable regen button, much like a disable traction control button. Or this could be accomplished with programming via a double tap or tripple tap of the regen on demand paddle.

Also, when coming off the freeway, on the off-ramps, I find the regen in D too strong with a complete pedal lift. I'm slowing much more that the gasoline cars in front and in back of me who are probably coasting with a complete pedal lift until they near the stop-sign at the end of the ramp.

I find I have to keep my foot on the go pedal until I am near the stop sign. I find that a little annoying.

 

[michaellax]

There are a few cases per month when I desire zero regen. Coasting on a 4% grade is a good example.

Could you explain this to me in a bit more detail?

Say you are on an Interstate approaching a 4% grade. You would prefer to "coast?" instead of regen, and then what happens when the road flattens out again? How are you taking advantage of the coasting, when you vehicle is going less than the minimum speed allowed on the interstate?

I bring up this question, because on Interstate-5 at the Grapevine going northbound at a 6% grade, I get in the right-most lane with the trucks that are limited to 35 MPH and use cruise control to regen 2.0 KW on this 5 mile stretch of downhill road and then of course utilize this 2.0 KW when driving on the flat section thereafter.

 

[michael]

Could you explain why you want no regen?

I'm guessing that it's because you want to coast at whatever speed the downhill naturally give you? But why not simply modulate the throttle, either with your foot or using the cruise control, to maintain whatever speed you want. You will either regen or consume energy as required, and if the slope would give a faster speed than you have selected, you will regain energy.

 

[ghn]

Could you explain why you want no regen?

I'm guessing that it's because you want to coast at whatever speed the downhill naturally give you? But why not simply modulate the throttle, either with your foot or using the cruise control, to maintain whatever speed you want. You will either regen or consume energy as required, and if the slope would give a faster speed than you have selected, you will regain energy.

I can explain this by an example. Say you were on a grade were you could take the car out of gear and coast at a steady 55mph. In this situation if you were in gear you would need to apply a certain amount of juice to overcome the drag of the drive train and maintain 55mph. There is gain from coasting in this situation. How much I do not know as I have not done any experiments to find out but coasting at the right time is a way to increase efficiency.

 

[michaellax]

If you are on a grade (the example was 4%, rather steep!), how can you keep the coasting at a safe speed without braking or regen?

 

[michael]

Could you explain why you want no regen?

I'm guessing that it's because you want to coast at whatever speed the downhill naturally give you? But why not simply modulate the throttle, either with your foot or using the cruise control, to maintain whatever speed you want. You will either regen or consume energy as required, and if the slope would give a faster speed than you have selected, you will regain energy.

I can explain this by an example. Say you were on a grade were you could take the car out of gear and coast at a steady 55mph. In this situation if you were in gear you would need to apply a certain amount of juice to overcome the drag of the drive train and maintain 55mph. There is gain from coasting in this situation. How much I do not know as I have not done any experiments to find out but coasting at the right time is a way to increase efficiency.

No, really there isn't. Supposes you're on a 55 MPH grade. Set the cruise control to that speed (or maintain it with your foot on the throttle) and no net energy will flow into or out of the battery.

The concept of "take the car out of gear" does not apply. There is no gear to disengage.

In the case of an ICE car, your approach would improve economy...engine drag and pumping losses would be avoided. You could in principle entirely shut down the engine, not use any gas at all. None of this applies to EVs. The drivetrain is always engaged.

 

[ghn]

Could you explain why you want no regen?

I'm guessing that it's because you want to coast at whatever speed the downhill naturally give you? But why not simply modulate the throttle, either with your foot or using the cruise control, to maintain whatever speed you want. You will either regen or consume energy as required, and if the slope would give a faster speed than you have selected, you will regain energy.

I can explain this by an example. Say you were on a grade were you could take the car out of gear and coast at a steady 55mph. In this situation if you were in gear you would need to apply a certain amount of juice to overcome the drag of the drive train and maintain 55mph. There is gain from coasting in this situation. How much I do not know as I have not done any experiments to find out but coasting at the right time is a way to increase efficiency.

No, really there isn't. Supposes you're on a 55 MPH grade. Set the cruise control to that speed (or maintain it with your foot on the throttle) and no net energy will flow into or out of the battery.

The concept of "take the car out of gear" does not apply. There is no gear to disengage.

In the case of an ICE car, your approach would improve economy...engine drag and pumping losses would be avoided. You could in principle entirely shut down the engine, not use any gas at all. None of this applies to EVs. The drivetrain is always engaged.

Okay I see your point if the electric motor is always spinning and putting the car in N simply disengages the regen?

 

[gpsman]

Charging (regen) and applying propulsion both have conversion losses. Mechanical to chemical to mechanical again. Heat is generated for example. Heat PLUS the frictional losses of the car. Plus added wear and tear is done to the battery, regardless of how slight.

Coasting only has the frictional losses of the car.

You can coast with the car in D or L.
But it's darn tricky.
Try keeping the power meter between 0 and 1 for 5 minutes straight at 55-65 mph. Bet ya can't.

"N" position on the center selector accomplishes this.

On moderate slopes, It is best to let gravity do all the work, as long as you are within speed limits. If you begin to exceed a safe or legal speed, of course you should use regen to slow down or hold the max.

-John

There are a few cases per month when I desire zero regen. Coasting on a 4% grade is a good example.

Could you explain this to me in a bit more detail?

Say you are on an Interstate approaching a 4% grade. You would prefer to "coast?" instead of regen, and then what happens when the road flattens out again? How are you taking advantage of the coasting, when you vehicle is going less than the minimum speed allowed on the interstate?

I bring up this question, because on Interstate-5 at the Grapevine going northbound at a 6% grade, I get in the right-most lane with the trucks that are limited to 35 MPH and use cruise control to regen 2.0 KW on this 5 mile stretch of downhill road and then of course utilize this 2.0 KW when driving on the flat section thereafter.

 

[ghn]

I have done a bit of experimenting with regen vs. coasting in 'N'. Several times I have been on slope where I could get the kw used to zero and then put the car into neutral. In every case there was an immediate increase in speed while coasting in 'N'. So as several posters have pointed out coasting is more efficient as long as you stay off of the friction brakes. For me the possible gain from coasting in 'N' at the perfect moment is not worth the effort required.

~gary

 

[michael]

I can explain this by an example. Say you were on a grade were you could take the car out of gear and coast at a steady 55mph. In this situation if you were in gear you would need to apply a certain amount of juice to overcome the drag of the drive train and maintain 55mph. There is gain from coasting in this situation. How much I do not know as I have not done any experiments to find out but coasting at the right time is a way to increase efficiency.

No, really there isn't. Supposes you're on a 55 MPH grade. Set the cruise control to that speed (or maintain it with your foot on the throttle) and no net energy will flow into or out of the battery.

The concept of "take the car out of gear" does not apply. There is no gear to disengage.

In the case of an ICE car, your approach would improve economy...engine drag and pumping losses would be avoided. You could in principle entirely shut down the engine, not use any gas at all. None of this applies to EVs. The drivetrain is always engaged.

Okay I see your point if the electric motor is always spinning and putting the car in N simply disengages the regen?

Yes.

Furthermore, try this (I have tried on a Volt, don't know for sure but I'm guessing it applies to a Bolt as well...)

In N, coasting, power consumption is approximately 0.5 kW. This represents, I imagine, thermal management, etc, all sorts of minor uses of power. You can set this value to zero by remaining in gear, modulating the throttle as necessary

Furthermore, when in gear, applying the brake causes regeneration. When in N, there is no regen, only the friction brakes.

Try this on a Bolt, see if it's the same.

Your observation about speeding up in N may be a consequence of this...in N you are slowly depleting the battery, due to the minor overhead consumption. By remaining in gear and adjusting the net power to zero, you are slowing slightly but keeping the battery at a constant level.

 

[SeanNelson]

...in N you are slowly depleting the battery, due to the minor overhead consumption. By remaining in gear and adjusting the net power to zero, you are slowing slightly but keeping the battery at a constant level.

...BUT if you're coasting with net power at zero, then the 0.5W that's powering everything else must be coming from regen - and that means, as you said, that you're robbing yourself of speed. That's not a problem if you're going downhill and you need to be keeping the speed down anyway, but if you're driving on level ground then sooner or later you're going to have to expend even more battery power to get back up to speed again, so your attempt at "saving" power would have been a false economy.

 

[ghn]

No, really there isn't. Supposes you're on a 55 MPH grade. Set the cruise control to that speed (or maintain it with your foot on the throttle) and no net energy will flow into or out of the battery.

The concept of "take the car out of gear" does not apply. There is no gear to disengage.

In the case of an ICE car, your approach would improve economy...engine drag and pumping losses would be avoided. You could in principle entirely shut down the engine, not use any gas at all. None of this applies to EVs. The drivetrain is always engaged.

Okay I see your point if the electric motor is always spinning and putting the car in N simply disengages the regen?

Yes.

Furthermore, try this (I have tried on a Volt, don't know for sure but I'm guessing it applies to a Bolt as well...)

In N, coasting, power consumption is approximately 0.5 kW. This represents, I imagine, thermal management, etc, all sorts of minor uses of power. You can set this value to zero by remaining in gear, modulating the throttle as necessary

Furthermore, when in gear, applying the brake causes regeneration. When in N, there is no regen, only the friction brakes.

Try this on a Bolt, see if it's the same.

Your observation about speeding up in N may be a consequence of this...in N you are slowly depleting the battery, due to the minor overhead consumption. By remaining in gear and adjusting the net power to zero, you are slowing slightly but keeping the battery at a constant level.

Good point and something that I had thought of. I could never get exactly zero on the energy used on these experiments and I always erred on the side of using kw as opposed to regen. The pickup in speed in my experience is rather noticeable. There is definitely drag reduction when in 'N' as the car seems to free wheel pretty good when out of gear. It is rather heavy...

 

[NeilBlanchard]

When you need to carry speed - coast.

When you need to slow down, use regen.

Having coasting in D means that you accelerate less, then coast, so you cover more distance using less energy.