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oilerlord
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Re: miles due to regeneration

Thu Aug 31, 2017 3:31 am

tstrobel wrote: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.
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tstrobel
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Re: miles due to regeneration

Thu Aug 31, 2017 12:13 pm

oilerlord wrote:
tstrobel wrote: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

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JerryBob
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Re: miles due to regeneration

Thu Aug 31, 2017 2:38 pm

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.
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SeanNelson
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Re: miles due to regeneration

Thu Aug 31, 2017 3:42 pm

JerryBob wrote: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
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Re: miles due to regeneration

Thu Aug 31, 2017 4:59 pm

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.

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oilerlord
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Re: miles due to regeneration

Tue Sep 05, 2017 3:56 am

NeilBlanchard wrote:

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.
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gpsman
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Re: miles due to regeneration

Tue Sep 05, 2017 5:13 am

PackardV8 wrote: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.

:D

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oilerlord
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Re: miles due to regeneration

Tue Sep 12, 2017 2:47 pm

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.
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sparkyps
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Re: miles due to regeneration

Thu Sep 14, 2017 6:56 pm

NeilBlanchard wrote: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
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Re: miles due to regeneration

Thu Sep 14, 2017 7:26 pm

sparkyps wrote:
NeilBlanchard wrote: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.
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