miles due to regeneration

[tstrobel]

Not sure this is the correct forum for my question, so admins please move if necessary...

My question is "Is there a way to determine how many 'extra' miles one has gotten thru regeneration?" I will occasionally see the estimated range go up slightly, but haven't found a setting to see how many extra miles of range due to proper use of "L" or coasting in D.

I suppose if i ended up with more than 238 on a charge, i can say "there's my extra", but i probably will never get down to empty...


Also, way off topic what do you call the pedal you step on to make the car go? :mrgreen: certainly isn't the gas pedal anymore!

 

[user 744]

Also, way off topic what do you call the pedal you step on to make the car go? :mrgreen: certainly isn't the gas pedal anymore!

"Accelerator" is the usual term.

 

[tstrobel]

Also, way off topic what do you call the pedal you step on to make the car go? :mrgreen: certainly isn't the gas pedal anymore!

"Accelerator" is the usual term.

Yeah, that makes sense

 

[PackardV8]

I suppose if i ended up with more than 238 on a charge, i can say "there's my extra", but i probably will never get down to empty...

Minor point, but when the battery is totally full, regeneration will no longer activate. That's why the Hilltop/Mountaintop setting tapers off charging before full; so regen can always be available. There are some EV owners, such as those who live in Park City and have a 20-mile downhill run into Salt Lake City. They can garner substantial additional charge during that run, if there's room in the battery to accept it.

jack vines

 

[NeilBlanchard]

Regenerative braking is a good thing - but it is not magic. The best you can expect is to use less energy - so if you drive efficiently, you will use less energy per mile.

Friction brakes are 100% loss, and regen is at least 50% loss - so better, but you will still lose energy.

It is most efficient to accelerate as little as possible, then coast - which loses 0% (other than parasitic losses which are always there anyway). Coast in any situation where you need to carry speed, and then use regen only when you need to slow down.

Think of it this way: if you accelerate all the time, and then use regen, you have accelerated too much, and regen will only regain some fraction of what you used.

If you accelerate and then coast - and then use regen, you have used less energy, then regained the maximum possible to carry the car forward WITH NO ADDITIONAL ENERGY. And then you don't need to use regen as much.

So, you use less, and use it better, and then still regain some energy.

 

[tstrobel]

Regenerative braking is a good thing - but it is not magic. The best you can expect is to use less energy - so if you drive efficiently, you will use less energy per mile.

Friction brakes are 100% loss, and regen is at least 50% loss - so better, but you will still lose energy.

It is most efficient to accelerate as little as possible, then coast - which loses 0% (other than parasitic losses which are always there anyway). Coast in any situation where you need to carry speed, and then use regen only when you need to slow down.

Think of it this way: if you accelerate all the time, and then use regen, you have accelerated too much, and regen will only regain some fraction of what you used.

If you accelerate and then coast - and then use regen, you have used less energy, then regained the maximum possible to carry the car forward WITH NO ADDITIONAL ENERGY. And then you don't need to use regen as much.

So, you use less, and use it better, and then still regain some energy.

not sure this tells me what i'm looking for. i guess the better, more "common" way would be "how many KWH did i recoup total"

 

[SeanNelson]

Friction brakes are 100% loss, and regen is at least 50% loss - so better, but you will still lose energy.

I think that might be a bit of a pessimistic estimate for regen efficiency, although I do agree that it is far less than 100%.

 

[redpoint5]

Friction brakes are 100% loss, and regen is at least 50% loss - so better, but you will still lose energy.

I think that might be a bit of a pessimistic estimate for regen efficiency, although I do agree that it is far less than 100%.

The conversion process is; kinetic > electrical > chemical > electrical >kinetic.

Perhaps the first part of converting kinetic energy into chemical is above 50% efficient, but completing the conversion back into useful kinetic energy doubles the losses.

50% is likely a reasonable estimate. Earlier vehicles were reportedly only 33% efficient at capturing and reusing kinetic energy (regen).

 

[Anonymous]

My question is "Is there a way to determine how many 'extra' miles one has gotten thru regeneration?"

When I drive from home in Los Angeles to Santa Cruz, I drive Interstate-5 up through the Grapevine to Hiway-46 west to US-101 in Paso Robles to a DCFC. This drive is 196 miles, but leaving Los Angeles I go uphill into the Los Angeles National Forest and burn more KWs than I would on a flat surface.

I seek to gain as much of these back as I can to make a comfortable drive to Paso Robles, especially with the air conditioning on in the hot Central Valley of California.

So going down the 5 miles of the 6% steep downhill grade of the Grapevine, I get in the rightmost "Truck" lane and follow one of these trucks.

Their speed limit is 35 MPH at this point, but many will go 40 MPH, even passing in the next lane those going 35!

I am not trying to "draft" these trucks; I am just trying to safely drive at the slowest speed possible for use of cruise control in "L" mode to maximize regeneration during these 5 miles.

I typically regenerate 1.5 KW at 45 MPH and 2.0 KW at 35 MPH.

So, doing the math at an average of 238 miles per 60 KW of full battery; recovering 2.0 KW will not only cause me to not use any energy during the 5 miles downhill of the Grapevine, but get me another 8 miles towards my trip to Paso Robles; for at least an extra 13 miles.

Not only can I drive more comfortably, but if there is a problem at the single CCS DCFC in Paso Robles, I can then drive the additional 30 miles to San Luis Obispo to use the DCFC there.

But of course, regeneration over the period of 200 miles, gives me much more than that!

 

[SeanNelson]

Friction brakes are 100% loss, and regen is at least 50% loss - so better, but you will still lose energy.

I think that might be a bit of a pessimistic estimate for regen efficiency...

The conversion process is; kinetic > electrical > chemical > electrical >kinetic.

Perhaps the first part of converting kinetic energy into chemical is above 50% efficient, but completing the conversion back into useful kinetic energy doubles the losses.

50% is likely a reasonable estimate. Earlier vehicles were reportedly only 33% efficient at capturing and reusing kinetic energy (regen).

Considering that the Volt's charger was found to be over 90% efficient, I'm still pretty skeptical that all the losses add up to that much. GM seems to have done a pretty bang-up job on the electrical systems in this car.

That being said, I of course wholeheartedly agree that momentum maintained is waste avoided.

 

[oilerlord]

Not sure this is the correct forum for my question, so admins please move if necessary...

My question is "Is there a way to determine how many 'extra' miles one has gotten thru regeneration?" I will occasionally see the estimated range go up slightly, but haven't found a setting to see how many extra miles of range due to proper use of "L" or coasting in D.

I suppose if i ended up with more than 238 on a charge, i can say "there's my extra", but i probably will never get down to empty...

That's a great question. I've wondered about that too, and would like to know how many kWh's were actually recovered. I'm guessing the data is there, but buried where only an OBD2 reader (or GM's own diagnostic equipment) may be able to access it.

 

[tstrobel]

Not sure this is the correct forum for my question, so admins please move if necessary...

My question is "Is there a way to determine how many 'extra' miles one has gotten thru regeneration?" I will occasionally see the estimated range go up slightly, but haven't found a setting to see how many extra miles of range due to proper use of "L" or coasting in D.

I suppose if i ended up with more than 238 on a charge, i can say "there's my extra", but i probably will never get down to empty...

That's a great question. I've wondered about that too, and would like to know how many kWh's were actually recovered. I'm guessing the data is there, but buried where only an OBD2 reader (or GM's own diagnostic equipment) may be able to access it.

I ordered an ODB2 reader last night. will be here tomorrow. I was watching the screen that says KWH used, and did see it "roll back" by .1 occasionally when braking

 

[JerryBob]

There is a hill here where we have coasting competitions. It is about 4 miles to coast down. I tried it with my i3 and had 2.5% more energy (22kw battery pack) at the bottom than when I started. I know someone who was doing the ICE to EV conversions and he had a switch to turn off the regeneration at freeway speeds because he said it used more energy to overcome the drag than it produced. Is there a sweet spot? This may or may not be an urban legend but it did improve the way the car drove without the drag on the freeway.

 

[SeanNelson]

I know someone who was doing the ICE to EV conversions and he had a switch to turn off the regeneration at freeway speeds because he said it used more energy to overcome the drag than it produced. Is there a sweet spot? This may or may not be an urban legend but it did improve the way the car drove without the drag on the freeway.

That doesn't make any sense. When you're going down a hill the drag is there whether you regen or not. If the grade is such that you need additional braking force to maintain a constant speed, there is no way that regen is less efficient than just using the friction brakes.

The only reason to "disable regen" would be if you wanted to keep accelerating to terminal velocity (the speed at which air resistance prevents any further increase in speed). Since regen provides braking force then it's pretty obvious you wouldn't want it in that situation.

 

[NeilBlanchard]

Regenerative braking will ALWAYS regain LESS energy than you used getting the car up to speed. So, regen only can reduce the energy you use, so your range increases.

Coasting can decrease the energy you use even MORE than regen can - because coasting loses less energy.

Here's what I do: I coast when I need to carry speed, and only use regen when I need to slow down.

My winter average in our Leaf was 4.7 miles / kWh, and my summer average is 5.3 miles / kWh. Our e-Golf is quite similar, but it doesn't keep a long term average.

 

[oilerlord]

Coasting can decrease the energy you use even MORE than regen can - because coasting loses less energy.

Here's what I do: I coast when I need to carry speed, and only use regen when I need to slow down.

This^^

It's the key to efficiency, applies to all vehicles regardless of regen. Regenerative braking only recovers a fraction of the energy spent in moving the car forward, so as much as some people think regen is an awesome way to put energy back into the battery, it isn't. In terms of efficiency - It's a bad deal.

 

[gpsman]

Minor point, but when the battery is totally full, regeneration will no longer activate. That's why the Hilltop/Mountaintop setting tapers off charging before full; so regen can always be available.

jack vines

That is not quite true.
100% charged battery does NOT disable regen charging. It reduces it to about 25% of normal strength though. Evidence that "full" means the software limit Chevy has chosen, and not chemically, full, scientifically speaking. I have never started with a 100% charged battery at the top of a long downhill slope. I suspect mile over mile the regen strength will decrease futher.... 20%...... 15%...... 10%....... 5%..... as the battery becomes chemically full, and you are then carrying more than 60 kwh with you.

 

[oilerlord]

From the information display, we know how much power is being consumed from HVAC and other accessories. Does that same display show how much energy is being recovered through regenerative braking? If not, the OP said he'd be hooking up an OBD2 reader to find out. Would be nice to know.

 

[sparkyps]

Regenerative braking will ALWAYS regain LESS energy than you used getting the car up to speed. So, regen only can reduce the energy you use, so your range increases.

Coasting can decrease the energy you use even MORE than regen can - because coasting loses less energy.

Here's what I do: I coast when I need to carry speed, and only use regen when I need to slow down.

My winter average in our Leaf was 4.7 miles / kWh, and my summer average is 5.3 miles / kWh. Our e-Golf is quite similar, but it doesn't keep a long term average.

Coasting is 0% efficient

Try this test, speed up to 30mph, coast to a stop. Measure energy recovered by coasting. Answer is 0

Now speed up to 30mph and regen brake to a stop. Measure energy recovered by Regen braking. Answer > 0

Regen braking is about 80% efficient at turning kinetic and potential energy into chemical energy in your battery.

 

[michael]

Regenerative braking will ALWAYS regain LESS energy than you used getting the car up to speed. So, regen only can reduce the energy you use, so your range increases.

Coasting can decrease the energy you use even MORE than regen can - because coasting loses less energy.

Here's what I do: I coast when I need to carry speed, and only use regen when I need to slow down.

My winter average in our Leaf was 4.7 miles / kWh, and my summer average is 5.3 miles / kWh. Our e-Golf is quite similar, but it doesn't keep a long term average.

Coasting is 0% efficient

Try this test, speed up to 30mph, coast to a stop. Measure energy recovered by coasting. Answer is 0

Now speed up to 30mph and regen brake to a stop. Measure energy recovered by Regen braking. Answer > 0

Regen braking is about 80% efficient at turning kinetic and potential energy into chemical energy in your battery.

Try this test:

Speed up to 30 MPH, coast to a stop. Note energy consumed...it's the amount it took to get to 30 MPH plus zero, as you say, from coasting. But put a marker by the road where you stop. Note how long it took you to reach that point from the beginning of the test.

Go back to beginning. Speed up to 30 MPH, brake to a stop. Note energy consumed. It will be > 0 because regeneration is not 100% efficient. Now continue driving until you get the the flag, brake to a stop. Get there in the same time it took you in the first test

You will find that the energy consumed in the second case, to go the same distance in the same time is much higher than in the first case because energy is wasted into heat, both during regeneration and during the following acceleration.

Every time energy make a round trip into and out of the battery, some is lost to heat.