Confused (Humorous) 2017 Volt

1916 Views 21 Replies 7 Participants Last post by wordptom, 2 mo ago

obermd

Discussion Starter · 2 mo ago

So between the cold weather, battery degradation (13.1 KWh to empty), and a somewhat hilly 50 mile round trip commute, I have been manually switching in and out of hold mode whenever I have a long downhill section of road. Several times I've seen my gas MPG higher than the trip MPG and I've even had a couple of days where the gas MPG topped out over 100 MPG (gas, not electric). I've been getting home most days with 50 to 55 MPG (gas). I've been doing this because I can drive an uphill mile on electric at about a third the price of gas. My tradeoff goal has been to extend the range of the expensive fuel by using it where it's most efficient - downhill. Note - all this driving has been at the posted speed limit and in the right lane except to pass when driving on multi-lane roads.

Now for the fun part - this morning my car wouldn't precondition and I realized this was a documented situation - the car was almost out of gas. I had expected to make one more day before the gas range switched to "LOW", but I went ahead and stopped for gas on the way to work this morning. When I was done filling my tank and got back into my car I took the picture below. Note the Fuel Range number. The EV range is about right for my commutes due to the cold weather.

Speedometer Gauge Vehicle Mode of transport Trip computer

About half a mile later I noticed the Fuel Range had gone up to 583 miles.

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arbus

· #2 · 2 mo ago

How cool. Maybe you're floating around the edge of the programming. I wonder what the maximum value is. Maybe you'll find out.

When I had my Accord hybrid (1.5 miles total electric range), I'd use EV mode to accelerate to +40 mph and then flip it to use the ICE. When I did that, in town, I could (according to the display) easily manage 70mpg, sometimes reaching more than 100mpg. Not doing that, I was in the low 50s over the same route.

Too bad the car wasn't smart enough to use the battery in that manner all by itself. EV acceleration is way more fun!

obermd

Discussion Starter · #3 · 2 mo ago

arbus said:
How cool. Maybe you're floating around the edge of the programming. I wonder what the maximum value is. Maybe you'll find out.

As far as I can tell the Volt will display up to 250 MPG. I know my wife's Honda Clarity PHEV maxes out at 199 MPG (won't display 200).

phattyduck

· #4 · 2 mo ago

obermd said:
I've been getting home most days with 50 to 55 MPG (gas).

I've been doing a bit of careful choices on when to use Hold vs. Normal on my commute too (76 miles round trip) since I know where the traffic (0-45mph) and highway speeds (60-72) will be along the way. Gas MPG in the 45-50mpg range, 100-120 MPGe for electric and a fully discharged battery at the end has been working well. Not really trying to be especially efficient though. Just about to 80k miles and have been getting mid 13's for kWh used - we shall see if that is permanent once the weather warms back up again (SoCal - not really cold - but enough to need the heater sometimes).

I have noticed that the computer will count downhill miles in Normal mode as gas miles if the hill was big enough (mountains, not hills) if you used the gas engine to get up the hill. Same with electric miles built up using Mountain mode

-Charlie

Lug_Nut

· #5 · 2 mo ago

obermd said:
I have been manually switching in and out of hold mode whenever I have a long downhill section of road.
My tradeoff goal has been to extend the range of the expensive fuel by using it where it's most efficient - downhill.

I'm puzzled.
If this is just a number's game, where ludicrous numerical displays are the goal rather than as an approximation of reality, then I get it.
If it's an intentional technique to actually reduce liquid fuel consumption, then I don't understand. Please elaborate when you 'switch in' and when you 'switch out' of hold mode.
I'd like to investigate if such a technique can be adapted to a gen1.

obermd

Discussion Starter · #6 · 2 mo ago

Lug_Nut said:
I'm puzzled.
If this is just a number's game, where ludicrous numerical displays are the goal rather than as an approximation of reality, then I get it.
If it's an intentional technique to actually reduce liquid fuel consumption, then I don't understand. Please elaborate when you 'switch in' and when you 'switch out' of hold mode.
I'd like to investigate if such a technique can be adapted to a gen1.

It's designed to reduce liquid fuel consumption. It costs me about four times as much to drive a mile on gas as on electric so the goal is to ensure each mile of gas is driven as efficiently as possible - i.e., downhill. I was amused that my Volt now thinks 60 to 65 MPG is the norm and is reporting estimated range based on this. As the weather gets warmer I'll be able to make my round trip commute on electric only.

As for whether it can be adapted to the Gen 1 Volt - as long as you have hold mode you can do this. What I have learned is that once the EV range drops to below 5 miles it's not worth the effort as I lose one to two miles of EV range while in hold mode as the 2nd gen Volt isn't very tight on the battery SOC while in hold mode.

wordptom

· #7 · 2 mo ago

obermd said:
It's designed to reduce liquid fuel consumption. It costs me about four times as much to drive a mile on gas as on electric so the goal is to ensure each mile of gas is driven as efficiently as possible - i.e., downhill. I was amused that my Volt now thinks 60 to 65 MPG is the norm and is reporting estimated range based on this. As the weather gets warmer I'll be able to make my round trip commute on electric only...

Sounds like you are saying that when the downhill slope is steep enough so that the force of gravity is sufficient to keep your car moving downhill at a steady speed (e.g., regen at the L level is needed to keep the car from accelerating downhill while using cruise control), then you save four times as much on fuel costs for each mile you drive downhill by driving downhill without using gas in Hold Mode than you would by driving downhill without using battery power in Normal mode.

obermd

Discussion Starter · #8 · 2 mo ago

wordptom said:
Sounds like you are saying that when the downhill slope is steep enough so that the force of gravity is sufficient to keep your car moving downhill at a steady speed (e.g., regen at the L level is needed to keep the car from accelerating downhill while using cruise control), then you save four times as much on fuel costs for each mile you drive downhill by driving downhill without using gas in Hold Mode than you would by driving downhill without using battery power in Normal mode.

It doesn't even have to be steep enough for regenerative braking. I'm driving in D and not accelerating. I'm getting some regeneration but mainly I'm running single digit KW, which is basically idle on the gas engine. I'm still burning through gas but in fractional gallons each day (0.07 to 0.14) but I'm going more than 50% further on that gas than I would be if I were just leaving the car in Normal mode all the time.

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obermd

Discussion Starter · #9 · 2 mo ago

2

So an update. I've driven 312 miles on this tank and when I got home today I saw these two displays. Note, I generally drive the posted speed limit or flow of traffic, whichever is slower. This is what you can do when you take advantage of the hills on your commute.

Vehicle Speedometer Plant Gauge Car

Land vehicle Vehicle Car Automotive design Motor vehicle

My battery depleted less than 100 feet from my house.

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wordptom

· #10 · 2 mo ago

There’s something unusual you don’t see every day... your trip Combined 86.1 MPGe is actually higher than the 80.7 MPGe when driving on battery power only.

dannyV

· #11 · 2 mo ago

Do you have any older pics of your energy screens for comparison? in my screens i was getting 115 to 130mpge..
So i wonder if you're just moving the mpge over to mpg. I've been trying your method and my mpg has gone up to about 47 from 43. Also you'll want to look into getting the myvolthold app for iphone and you can keep it in "hold electric mode" for that last mile home and use more of the hidden battery kw.

obermd

Discussion Starter · #12 · 2 mo ago

wordptom said:
There’s something unusual you don’t see every day... your trip Combined 86.1 MPGe is actually higher than the 80.7 MPGe when driving on battery power only.

Note the final MPGcs (gas) number - 109 MPG.

dannyV said:
Do you have any older pics of your energy screens for comparison? in my screens i was getting 115 to 130mpge..
So i wonder if you're just moving the mpge over to mpg. I've been trying your method and my mpg has gone up to about 47 from 43. Also you'll want to look into getting the myvolthold app for iphone and you can keep it in "hold electric mode" for that last mile home and use more of the hidden battery kw.

The images I posted are unusual for the end of the commute as I usually see the gas MPG in the low to mid 60s. I see the MPG inversion about once a week near the end of the final downhill stretch on the freeway before I start my final 7 mile, ~400 ft climb to my house. Still, my Volt's gas tank guess-o-meter is reflecting a gas MPG somewhere around 65 MPG using the electric uphill/gas downhill technique on my daily commute.

I use the bottom buffer daily over the last 200 yards to my house. There's a stop sign about 200 yards from my house and after I turn onto my residential street I keep the power requirements below 10 or 11 KW and the gas engine almost never comes on, even if the car is telling me it should be on. The two and half miles prior to that are all uphill. The final 7 mile profile is below.

Product Rectangle Font Parallel Screenshot

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dannyV

· #13 · 2 mo ago

I would think going down hill should be charging regardless of mode

obermd

Discussion Starter · #14 · 2 mo ago

dannyV said:
I would think going down hill should be charging regardless of mode

If you're referring to my chart, the left end is the exit from the freeway and the right end is my home at 5,700 ft above sea level. The short steep spot after then end of the gradual uphill is just shy of two and a half miles from my house. This section is steep enough that it takes as much energy to drive it as it does the two longer flat sections that precede it.

wordptom

· #15 · 2 mo ago

obermd said:
Note the final MPGcs (gas) number - 109 MPG.

My point is that when planning a daily round trip commute that includes significant changes in elevation, you can take advantage of the Volt Fuel Accounting Rules to maximize the gas mileage by using Hold Mode whenever you drive downhill, but doing so won’t necessarily minimize gas consumption for the round trip commute.

Seems to me if the downhill slope is long and steep enough to allow you to "coast" downhill in D, or to maintain a steady speed using cruise control, with L to keep from accelerating, then your downhill momentum is being maintained by the force of gravity, not by gas propulsion or electric propulsion. If, as you wrote earlier in the thread, you’re mostly "idling" the engine in Hold Mode while descending, you’re not really using gas for propulsion. And if the force of gravity is more than sufficient to maintain your speed, then the excess gravitational energy can be used to crank the generator to keep the car from accelerating.

And if gravity was used to crank the generator to prevent the car from accelerating, once you reach the bottom of the hill, you can drive a certain additional distance using regen-battery power and the electric motor. In effect, the downhill distance plus the regen-powered distance is fueled by the force of gravity. Fuel accounting rules determine if that distance is recorded as Gas Miles or Electric Miles.

You say your electric uphill/gas downhill technique is designed to reduce liquid fuel consumption on the round trip commute, but a single example, during which total gas consumption was only 0.10 gallons of gas for 12.2 gas miles of driving, provides no comparison to an alternate technique that requires greater consumption of gas. On level terrain, 0.1 gallons used in Hold Mode in a Gen 2 Volt might be sufficient to drive only 4.2 Gas Miles. Does driving downhill really magnify gas propulsion efficiency to the point where the car can be propelled three times as far per unit of gas (12.2 miles vs 4.2)?

Or does the real "gas mileage magic" come from using gravity to provide the downhill propulsion while recording the Hold Mode distances in the Gas Miles column?

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obermd

Discussion Starter · #16 · 2 mo ago

wordptom said:
My point is that when planning a daily round trip commute that includes significant changes in elevation, you can take advantage of the Volt Fuel Accounting Rules to maximize the gas mileage by using Hold Mode whenever you drive downhill, but doing so won’t necessarily minimize gas consumption for the round trip commute.

Seems to me if the downhill slope is long and steep enough to allow you to "coast" downhill in D, or to maintain a steady speed using cruise control, with L to keep from accelerating, then your downhill momentum is being maintained by the force of gravity, not by gas propulsion or electric propulsion. If, as you wrote earlier in the thread, you’re mostly "idling" the engine in Hold Mode while descending, you’re not really using gas for propulsion. And if the force of gravity is more than sufficient to maintain your speed, then the excess gravitational energy can be used to crank the generator to keep the car from accelerating.

And if gravity was used to crank the generator to prevent the car from accelerating, once you reach the bottom of the hill, you can drive a certain additional distance using regen-battery power and the electric motor. In effect, the downhill distance plus the regen-powered distance is fueled by the force of gravity. Fuel accounting rules determine if that distance is recorded as Gas Miles or Electric Miles.

You say your electric uphill/gas downhill technique is designed to reduce liquid fuel consumption on the round trip commute, but a single example, during which total gas consumption was only 0.10 gallons of gas for 12.2 gas miles of driving, provides no comparison to an alternate technique that requires greater consumption of gas. On level terrain, 0.1 gallons used in Hold Mode in a Gen 2 Volt might be sufficient to drive only 4.2 Gas Miles. Does driving downhill really magnify gas propulsion efficiency to the point where the car can be propelled three times as far per unit of gas (12.2 miles vs 4.2)?

Or does the real "gas mileage magic" come from using gravity to provide the downhill propulsion while recording the Hold Mode distances in the Gas Miles column?

These are good questions, but based on several decades of using efficient driving techniques as well as using mountain mode last winter (2021-2022) to ensure I finished the final 7 miles on battery I can definitely say yes, the car is using less gas that it would if I just let the battery run to empty and then switch over to gas.

Lug_Nut

· #17 · 2 mo ago

For finessing the calculations to generate a large number of the display: Well done, very clever.
For actually reducing fuel consumption: I think there's improvement possible.

The round trip in the example used 13.0 kWh for 37.4 miles, (not so good), and .1 gallons for 12.2 miles (really good), but the combined 86.1 MPGe is only so-so for 50 miles.
I expect that battery range from my 10 kWh gen1. Give me 13 kWh and I'd be able to do 50 miles of my typical driving with zero gasoline.
As it is, I get 40 miles per 10 kWh battery output, then would burn about .26 gallons for the next 10 (38 mpg average). Combined: 50 miles driven using .26 gallons for 192 "MPGe".
My out and back is obviously different, travel speeds are likely different as well, but different enough to explain the 225% difference in MPGe?

The combined distance of 49.5 miles at a combined 86.1 "MPGe" indicates that the actual fuel consumed was .575 gallons. To go 12.2 miles? 21.2 mpg?
Ficticious MPG display? Yeah, I've had "130" mpg shown at the end of a drive. Short ICE use distance, the (gen1) 0.0125 gallon resolution, and 'rounding up' (0.00, 0.03, 0.05, 0.08 steps) can make the implied math wildly variable and not to be believed.

The dubious technique barely described would not be possible in my gen1 Volt.
When I select 'hold' in my gen1, it does not initiate the ICE until the SOC has dropped to below the level when 'hold' was selected.
Were I on a down hill where "I'm getting some regeneration .." the ICE does not start. SOC has not dropped since hold was selected.
If the slope is shallow, or my desired speed is high and "I'm running single digit KW" the ICE doesn't start immediately when "hold" is selected, but only after the SOC has dropped by some amount, and at that, the ICE doesn't begin the charging restoration to the level when 'hold' was selected until the ICE has completed its warm up process.

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obermd

Discussion Starter · #18 · 2 mo ago

So I figured out yesterday why I saw such a huge jump from the normal 60 MPG gas reading I see when I get home. I tried the same thing and then paid attention to the gas mpg reading. From about 48 MPG, which is where it started after my stretch of gentle downhill earlier in the commute, I flipped to Hold as I crested the high point on my drive. I switched back to Normal mode at the end of the descent. My Volt had regenerated enough energy that I drove the next several miles on "gas" due to the way energy is accounted for in this system. Normally that descent can regenerate 0.2-0.3 KW for the battery, leading to the misleading 100+ mpg reading. At the end of yesterday's experiment my Volt showed 139 MPG on gas but since I was paying attention to what the car did off-freeway I know that's spurious and inaccurate. What this does show is just how much more efficient electric cars are than gas cars, though.

phattyduck

· #19 · 2 mo ago

obermd said:
My Volt had regenerated enough energy that I drove the next several miles on "gas" due to the way energy is accounted for in this system.

Yes. It absolutely accounts for (to the best it can) ascents and descents as part of the energy accounting process. I often put my Volt back into battery mode at the top of the hill before work (2-3 mile downhill at/near 0kW usage) - and often get to work around the time is switches back to using miles as 'battery' instead of 'gas'.

In general, if you MUST use gasoline on a trip, it is best to do it at higher speeds. Loading the engine up improves engine efficiency, so that is the best time to burn fuel. Constant mid-load running (instead of starting and stopping and likely slowly warming up) will also be marginally better for the engine.

-Charlie

obermd

Discussion Starter · #20 · 2 mo ago

phattyduck said:
Yes. It absolutely accounts for (to the best it can) ascents and descents as part of the energy accounting process. I often put my Volt back into battery mode at the top of the hill before work (2-3 mile downhill at/near 0kW usage) - and often get to work around the time is switches back to using miles as 'battery' instead of 'gas'.

In general, if you MUST use gasoline on a trip, it is best to do it at higher speeds. Loading the engine up improves engine efficiency, so that is the best time to burn fuel. Constant mid-load running (instead of starting and stopping and likely slowly warming up) will also be marginally better for the engine.

-Charlie

Yep - all my Hold modes are at 65 MPH.

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