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So after about a 10 mile decent from the summit of White Pass, WA my EV range was at 80 miles. I have never seen it this high. I was in "normal" mode during the decent and despite the 80 mile EV range the gas engine was still running during the decent...with no load on the engine, why was it running? Just prior to reaching the summit of white pass I was in "hold" mode and had an EV range of 49 miles. At the beginning of the descent I switched to "normal" mode and was interested to see what kind of range I could pick up as a result of the steep decline...I expected to pick up a few miles....but not the 20+ miles I got. And how does the "excess" energy get dissipated.?
Was I doing any damage to the system as a result of this excess regen? I got home from my trip with just 5 miles of EV range left and the overall mileage for the trip was in excess of 50 MPG. Very pleased with how the Volt performed on this trip even with the 18 degree temps in Yakima. Preconditioning on L2 in Yakima gave us a toasty cabin before departure and an EV range of 50 Miles to start the trip. Drove in fairly slippery snow in Yakima without any problem.
We were lucky in that the highway was well plowed and de-iced and thus the ascent and descent were no problem. Good thing as I just have the stock tires and did not carry chains.
 

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So after about a 10 mile decent from the summit of White Pass, WA my EV range was at 80 miles. I have never seen it this high. I was in "normal" mode during the decent and despite the 80 mile EV range the gas engine was still running during the decent...with no load on the engine, why was it running? Just prior to reaching the summit of white pass I was in "hold" mode and had an EV range of 49 miles. At the beginning of the descent I switched to "normal" mode and was interested to see what kind of range I could pick up as a result of the steep decline...I expected to pick up a few miles....but not the 20+ miles I got. And how does the "excess" energy get dissipated.?
Was I doing any damage to the system as a result of this excess regen? I got home from my trip with just 5 miles of EV range left and the overall mileage for the trip was in excess of 50 MPG. Very pleased with how the Volt performed on this trip even with the 18 degree temps in Yakima. Preconditioning on L2 in Yakima gave us a toasty cabin before departure and an EV range of 50 Miles to start the trip. Drove in fairly slippery snow in Yakima without any problem.
We were lucky in that the highway was well plowed and de-iced and thus the ascent and descent were no problem. Good thing as I just have the stock tires and did not carry chains.
You did not state what your battery SOC was as you began your descent. If the battery was almost fully charged then regen would put excess energy back into the battery until it was full, then regen would suspend. You would not damage any part of the Voltec drive system but if you are going to begin a long descent it is more efficient, with less wear on your friction brakes, if your battery is no more than ~50 to 60% charged. At the completion of your descent your battery could wind up being fully recharged.

The estimated EV range is computed by the Volt's algorithm considering speed, battery SOC, temperature and terrain. The downhill terrain added additional EV miles to the estimate.
 

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Discussion Starter #3
I had an EV range of 49 miles at the beginning of my descent. It almost felt like maybe the regen was restricted and the engine was running to provide some kind of compression braking in lieu of regen. The vehicle ran fine and there were no error messages, I just felt concerned about seeing the EV range climb to as high as 80 miles in normal mode (shifter in L position...as that is what I always use).
Why would the engine be running during a descent with no load on the vehicle at about 45-50 mph behind slow traffic with such excess EV range available?
 

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I had an EV range of 49 miles at the beginning of my descent. It almost felt like maybe the regen was restricted and the engine was running to provide some kind of compression braking in lieu of regen. The vehicle ran fine and there were no error messages, I just felt concerned about seeing the EV range climb to as high as 80 miles in normal mode (shifter in L position...as that is what I always use).
Why would the engine be running during a descent with no load on the vehicle at about 45-50 mph behind slow traffic with such excess EV range available?
Your EV range is NOT a measure of how much charge there is in the battery. It is an ESTIMATE of how far you MIGHT be able to drive with the current SOC. It is impossible to over charge a Volt.
 

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Your EV range is NOT a measure of how much charge there is in the battery. It is an ESTIMATE of how far you MIGHT be able to drive with the current SOC. It is impossible to over charge a Volt.
So, based on what you are saying, if I had been able to descend even further I might have been able to extend my estimated EV range by even further than 80 miles? I thought there was a limit to how much energy or "range" that could be stored in the battery. (in other words my Gen II Volts battery can only hold so much energy and therefore has a MAX EV range potential)
 

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As to the engine running on your descent, you mentioned it was 18F The engine will run at cold temperatures, with a user selectable choice of engage temperatures, either 15F or 35F. This is the "Engine running due to temperature" (ERDTT) that gets lots of discussion each winter, it's meant to help with cabin heat / defrost.

Do you know which setting you are using on your car? Could it have been colder than 15F at the summit?

-Lumos
2014 gen 1
 

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So, based on what you are saying, if I had been able to descend even further I might have been able to extend my estimated EV range by even further than 80 miles? I thought there was a limit to how much energy or "range" that could be stored in the battery. (in other words my Gen II Volts battery can only hold so much energy and therefore has a MAX EV range potential)
Your battery can only hold a max charge of 18.4 kWh, no more. Depending on how you drive, uphill, down hill, fast, slow, speed, wind, temperature, tire pressure, and HVAC settings, your range can vary anywhere from ~20 miles to at least 80 miles (as you found out).
As an extreme example, imagine you driving down a hill that is infinite (never ends), your range would eventually read "infinity" and you would never run out of charge. On the other hand if you were driving up the infinite hill your range would probably read less than 20 miles and you would quickly run out of charge.
 

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So, based on what you are saying, if I had been able to descend even further I might have been able to extend my estimated EV range by even further than 80 miles? I thought there was a limit to how much energy or "range" that could be stored in the battery. (in other words my Gen II Volts battery can only hold so much energy and therefore has a MAX EV range potential)
Your are forgetting that range estimates consist of two factors, not one: how much power is available, and how far can you drive per unit of power. The battery can hold only a fixed maximum amount of power. How far you can drive per unit of power is related to the terrain, the environment, and your driving habits. Maximum "range" is limited only by distance per unit of power.

You started your trip with a 50-mile range estimate, then flipped into Hold mode, so the range estimate was only down to 49 miles as you started the descent. Regen doesn’t give you "miles," it gives you battery power. The 49-mile estimate suggests you hadn’t yet used much battery, so there wasn’t much room for downhill regen to be added. Regenerative braking would have stopped functioning once the system prevented it from further recharging the battery. Perhaps the car was using the engine to provide an alternative instead of requiring you to use friction braking (this topic has had lots of discussion). Perhaps the amount of power in the battery at the bottom of the hill was not much more than what was there at the top of the hill.

Driving downhill certainly improved your mileage rate, though. At the bottom of the descent, the computer was estimating that if you could maintain that high ev mileage rate, you had enough available battery power to drive 80 more miles.

That’s not 80 miles of range. That’s 80 miles at that rate of power consumption range.

You arrived home with 5 miles of range left. Is your home 75 electric miles from the bottom of that descent? Or did the ev range drop faster than the distances driven once the terrain had changed?
 

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Your battery can only hold a max charge of 18.4 kWh, no more. Depending on how you drive, uphill, down hill, fast, slow, speed, wind, temperature, tire pressure, and HVAC settings, your range can vary anywhere from ~20 miles to at least 80 miles (as you found out).
As an extreme example, imagine you driving down a hill that is infinite (never ends), your range would eventually read "infinity" and you would never run out of charge. On the other hand if you were driving up the infinite hill your range would probably read less than 20 miles and you would quickly run out of charge.
Too bad I can’t drive to and from work, both ways, down hill.
 

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Discussion Starter #10
Too bad I can’t drive to and from work, both ways, down hill.
Yes, driving downhill in the Volt gives you a very good feeling as you watch the EV Miles guessometer increase !
I gather from others comments that going downhill for long distances does not hurt the battery from the extended re-gen.
It was about 18 degrees at the summit, but I don't think this was a factor as the engine had been running (on hold mode) for the entire ascent. I switched to normal mode at the beginning of my descent and the engine was at around 200 degrees and the cabin was toasty warm from the trip up to that point. So I am still a bit puzzled as to why the engine would be running at all during the descent since it was not required for cabin heating or for propulsion power.
The next time I make this trip I will try and duplicate the conditions BUT I will make one change. And that is I will make the descent in D instead of L.
I should also have maybe mentioned that the car in front of me during the descent was going pretty slow at times and slowing down often for curves due to potential ice on the road. I was using ACC and it did a good job of keeping my distance from that car in front.
The Volt is quite an amazing and complex drive system and I wish I understood all of its nuances better.
 

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. So I am still a bit puzzled as to why the engine would be running at all during the descent since it was not required for cabin heating or for propulsion power.
The next time I make this trip I will try and duplicate the conditions BUT I will make one change. And that is I will make the descent in D instead of L.
Could have been running due to temperature, ERDTT. It doesn't matter how hot it is in the cabin, the trigger is the outside air temp. Do you have it set at the default of 35F or 15F?

You likely won't like driving down this mountain in "D". You will find that the car will continue to accelerate and you will have to ride the brake pedal to control your speed. This is where "L" shines. On most down slopes "L" will keep the car from accelerating and you may even have to accelerate to keep from slowing too much.
 

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The next time I make this trip I will try and duplicate the conditions BUT I will make one change. And that is I will make the descent in D instead of L.
If you decide to take this trip again you can maximize your energy recovery if you start your descent with the battery state of charge (SOC) at ~ 50 - 60%, not higher. The battery state of charge is displayed on Driver Information Center as a 10 segment green ring on the left side of the display. Each segment represents approx. 1.41kWH of available battery capacity for a total of 14.1kWH, even though the battery capacity is 18.4kWH you are not able to fully charge or discharge the full capacity of the Volt's battery. Note that unlike the EV range that is displayed the battery SOC is not an estimate but a real-time display of the battery's actual charge. Here is a photo: https://www.google.com/search?q=chevy+volt+driver+information+console&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi_76C746rYAhVkg-AKHVcJA1UQ_AUICygC&biw=1360&bih=623#imgrc=Ssd69XOx12WV5M:
 

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Discussion Starter #13
Could have been running due to temperature, ERDTT. It doesn't matter how hot it is in the cabin, the trigger is the outside air temp. Do you have it set at the default of 35F or 15F?

You likely won't like driving down this mountain in "D". You will find that the car will continue to accelerate and you will have to ride the brake pedal to control your speed. This is where "L" shines. On most down slopes "L" will keep the car from accelerating and you may even have to accelerate to keep from slowing too much.
I agree that driving in L makes more sense in a long descent. Next time I will use up more of the battery BEFORE I start the descent.
 

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Yes, driving downhill in the Volt gives you a very good feeling as you watch the EV Miles guessometer increase !
I gather from others comments that going downhill for long distances does not hurt the battery from the extended re-gen.
It was about 18 degrees at the summit, but I don't think this was a factor as the engine had been running (on hold mode) for the entire ascent. I switched to normal mode at the beginning of my descent and the engine was at around 200 degrees and the cabin was toasty warm from the trip up to that point. So I am still a bit puzzled as to why the engine would be running at all during the descent since it was not required for cabin heating or for propulsion power.
The next time I make this trip I will try and duplicate the conditions BUT I will make one change. And that is I will make the descent in D instead of L.
I should also have maybe mentioned that the car in front of me during the descent was going pretty slow at times and slowing down often for curves due to potential ice on the road. I was using ACC and it did a good job of keeping my distance from that car in front.
The Volt is quite an amazing and complex drive system and I wish I understood all of its nuances better.
If you are g ping up the mountain, you should be in mountain mode.
 
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