[srmarti]

I believe at some point the engine might have been motoring to provide drag as the battery charge was already at maximum. Maybe that explains the no gas "gas miles"


Further checking, I think it does not spin the engine. It works the motors against each other and dissipates the heat.

 

[HighRollsVoltDriver]

Downhill every day and never have a full green ball

I live on a mountain and go 2700 feet downhill over 9 miles each day starting with a fully charged battery. Therefore the energy display shows about 3 to 4 gas miles all the time without having used any gas. Always a blue slice in the energy pie! It is kind of bothering me because this is a an easily fixable software glitch, I would think.

Also I am wondering where the excess energy goes when the battery can´t take any charge any more. Something must get hot! For about 2 downhill miles I notice some oscillations in accelleration and retardation. The display switches from 1KW REGEN to about 8KW USED for about 5 seconds followed by a decelleration for a couple of seconds. It does this 7 or 8 times and then the car just gets faster so that I have to use the wheel brakes for the rest of the downhill. Speed limit is 50MPH. It easily would go to 80 or faster.

I would like to have a software feature where I can limit the charge to 75% SOC. At the bottom of the hill I would be at 87% which appears to be the charge limit of the 2013 VOLT battery.

An interesting future option for EV accessory makers would be some kind of an "overflow" storage device like a capacitor that can store 1KWH of electricity for a short period of time. I know that Toyota uses this kind of storage in their Le Mans Endurance Race Cars. Or a flywheel maybe? That is what Audi uses in their R18 E-Tron racer.

During winter I use full heat during the downhill portion and switch to eco once the display switches from REGEN to USE. During summer I do the same with the AC.

Delayed charge is not really an option because my work schedule is different almost every day. And for any unplanned drive late in the evening I would like to have a charged battery too.

All this may sound like an issue that only a few "mountain" people have, but for my next EV purchase this will definetly be an important detail.

 

[No Ohms]

Also I am wondering where the excess energy goes when the battery can´t take any charge any more. Something must get hot! For about 2 downhill miles I notice some oscillations in accelleration and retardation. The display switches from 1KW REGEN to about 8KW USED for about 5 seconds followed by a decelleration for a couple of seconds. It does this 7 or 8 times and then the car just gets faster so that I have to use the wheel brakes for the rest of the downhill. Speed limit is 50MPH. It easily would go to 80 or faster.

Very interesting indeed. I have heard that once the battery SOC is full, the Volt will engage both the 55 kW generator and 111 kW traction motor to fight with each other for awhile until a thermal limit is reached.

No Ohms
#1 Voltstats.net - Overall Category (299.99 Points)
#1 Voltstats.net - Most Electric Miles Driven in a Day (434.57)

 

[canehdian]

This begs the question, though:
Why would you charge up at the top of a mountain?
It's just going to go to waste as you've got nowhere to regen. Might as well leave it empty and fill right back up.
If its the exact same distance/elevation going back down, I could see topping up to 20% or something to account for inefficiency in regen (so you end up actually full by the bottom), but certainly not any higher.

 

[HighRollsVoltDriver]

Hot brakes in the morning and ICE coming on just in front of the garage.

This begs the question, though:
Why would you charge up at the top of a mountain?

Because that´s where I live and where my Level 2 charger is.

It's just going to go to waste as you've got nowhere to regen.

That is exactly the problem. And that´s why an "overflow" capacitor would be great!

Might as well leave it empty and fill right back up.

Did that with half empty battery. From the downhill REGEN I get about 1.2KWH charge. Little more than 10% of the battery capacity. Not enough to go to work and back home.

If its the exact same distance/elevation going back down, I could see topping up to 20% or something to account for inefficiency in regen (so you end up actually full by the bottom), but certainly not any higher.

That´s why I would like to have the option to just charge to 75% battery state of charge (SOC). That would give me a fully charged battery at the bottom of the mountain without any wasted energy.
It takes 3.6KWH up the mountain at given speed limit and I get 1.2KWH back during downhill REGEN. A 3 to 1 ratio.

My daily commute is 22 miles one way. 9 Miles downhill with described issue, then 13 miles level at 50 to 60 miles MPH on 4 lane Highways. Arrive at work with still 58 to 60 displayed EV miles to go. No charge at work. On the way home I have 25 EV miles to go on the display with 6.7 KWH used at the bottom of the mountain. Normally I JUST make it home without ICE coming on. In the summer I see about 2 EV miles left and 10.5KWH used when I hit my garage. In winter ICE often comes on during the last mile. Painful ICE coldstart for a minute or so!! A semi truck in front of me during the uphill drive without a chance to pass him makes my day. Going 30MPH uphill instead of the 50MPH speed limit gives me THE extra mile.

I know, I am right on the edge of VOLT´s envelope! Little things make the difference during my daily driving! Hard braking for a late red light takes the last mile away from me, strong southwesterly tailwinds on the way home give it back. I hate it most, when the ICE comes on just before I drive into my garage. Then I really wish I had that extra juice that I had converted into waste heat earlier that day during the downhill drive.

Although, since I am a positive thinking guy, I have to say: Each day I have a challenge! I play Bob Hoover´s game of energy management. (Anybody has seen that WWII pilot´s airshow with his AERO COMMANDER shutting down both engines, flying a Looping in front of the crowd, then turns into a downwind pattern, lands and stops his airplane right in front of the center grand stand?)
10.4 KWH NO ICE DAYS are good days. And I love my VOLT!

 

[SteveC5088]

If I lived at the top of a grade that I had to descend every day, I think I would try to find some method of stopping the charging, using a timer or some similar device, so I had a little empty reserve on the battery that the car could use on the descent.

Seems like the net effect of a full charge before the descent is a double problem: That last kwh or more is just wasted energy, and since the Volt has no place to store the energy descending, you wear out your brake pads and rotors as well.

 

[SteveC5088]

I recently found this web site: Predicting Energy Use. These people created some guidelines using a Miev and a Leaf: They estimated the cars use .25 kwh per mile on flat ground, and use 1.5 kwh per 1k elevation climb. (Incidentally, they also found a gain of 1 kwh per 1k descent.)

It is interesting the No Ohms' climb numbers above show:
net climb: _ 3800'
miles: _ _ _ _ 12
kwh: -_ _ _ _ 8.1

Using the PEU site's numbers, it would have required 3 kwh to travel the 12 miles, and 5.7 kwh for the climb, for a total of 8.7 kwh. The .6 kwh difference is only a 7% variation.

 

[srmarti]

An interesting future option for EV accessory makers would be some kind of an "overflow" storage device like a capacitor that can store 1KWH of electricity for a short period of time. I know that Toyota uses this kind of storage in their Le Mans Endurance Race Cars. Or a flywheel maybe? That is what Audi uses in their R18 E-Tron racer.


All this may sound like an issue that only a few "mountain" people have, but for my next EV purchase this will definetly be an important detail.

Then someone else will overflow the overflow device. I guess using comfort mode might help a bit. A remote prestart before you leave could use up an little and make room.

 

[No Ohms]

GPS Location Info to Prevent Cold Engine Start

Then someone else will overflow the overflow device. I guess using comfort mode might help a bit. A remote prestart before you leave could use up an little and make room.

So, this maybe a little overkill, (or should I correct myself already and say DEFINITELY overkill) but I've always thought a little 4 foot by 4 foot trailer with another 20 kWh of storage capacity would be fun. One would increase the towing weight by about 500 pounds, and a little more two wheel rolling resistance, but one would yield another 40-50 miles of range. Probably more (or less) practical for a Battery-only EV, since the Volt has an onboard generator anyway.
But, I do know the frustration of having the engine kick in just a mile or two from home on a cold start. Too bad the GPS doesn't know the Volt is so close to home, and lets it use a little reserve capacity to prevent a cold start. This would be close to what it does when the Volt is out of battery and gas. Let's you drive another 5 miles or so into the battery buffer. A software tweak would be wonderful for GPS! But, the bright side is, the Volt won't get stuck anywhere when the battery runs out (with gas in the tank!)

No Ohms

#1 Voltstats.net - Overall Category (299.99 points)
#1 Voltstats.net - Most Electric Miles Driven in a Day (434.57)

 

[canehdian]

Because that´s where I live and where my Level 2 charger is.

Was more a question for OP, whose drive seems to be mostly just up the mountain and back down the next day (and doesn't sound like this is an everyday thing)
Whereas yours is mostly flat after the mountain - makes sense to charge to some intermediate level.

You likely know how long it normally takes to charge to 75% or so, try setting an off-peak window of just a couple hours and set the car to only charge only off-peak. That might do the trick.

 

[No Ohms]

Was more a question for OP, whose drive seems to be mostly just up the mountain and back down the next day (and doesn't sound like this is an everyday thing)
Whereas yours is mostly flat after the mountain - makes sense to charge to some intermediate level.

You are correct, in that this is not an every day thing for me. I was just curious to see what would happen first hand with the Volt in this kind of scenario. Since I was visiting friends, I figured I'd take the opportunity to get some real world numbers with my Volt.

The ascent up the mountain was everything I had expected. But, on the descent, it was very interesting for me to witness first hand how the number of kWh used rolled back to zero. Then, very interesting to see, and was completely unexpected, to witness this mysterious phantom gas use on the display, with 0.00 gallons of gas used over an aggregated distance of 3.9 miles. It was fascinating how the car was behaving differently in Low with much less regen. ( I usually drive Sport/Low unless I am aggressively hyper-miling.) Interesting to use the brakes and not see kWh regenerated back to the batteries. And fun to drive almost 70 miles at normal highway speeds on all electric. So, this is why I charged the Volt at the top of a mountain. I am still just having too much fun with this Volt even after 14 months of ownership!

No Ohms
#1 Voltstats.net - Overall Category (299.99 points)
#1 Voltstats.net - Most Electric Miles Driven in a Day (434.57)
Lifetime 93.5 % Electric, 356 MPG

 

[vdiv]

The Prius also has an ICE Spin mode used all the time since the battery it has is tiny. It looks like the buffer the Volt has after the battery is "fully charged" is also small, it has to be to keep the battery longevity. The HVAC in Comfort mode would only shave off a few kW, that will hardly make a difference. Sounds like we have found yet another case for a bigger battery in the Volt and smarter chargers

 

[canehdian]

Oh, and it doesn't look like the 'phantom gas' was explained.
It's believed to just be a software 'feature' ("it's not a bug, its a feature!")
In that the computer sees all this power coming from seemingly nowhere, and battery is full. Therefore, must be from gas.
So it will then count gas mileage until you drop back down to normal levels.

 

[srmarti]

An overflow device of last resort might simply be a resister to dissipate excess power once the battery is fully charged. Seems unlikely to be cost effective to have more storage capacity just in case one goes down a big mountain. The Volt is apparently already doing something similar with the motors and cooling system.

 

[Volt Dolt]

If you want to charge the Volt to 75% and then have it stop charging, you can do it using programming available to you in the Volt already. Read up on how to program the Volt for on peak / off peak utility rates. Assuming you have an L2 charger, you can tell the Volt the off-peak period is between midnight and 2:30 AM. It will charge for 2.5 hours and shut off. If you start with an empty battery, that will be around 75%. Adjust the times as needed to get the charge you want.

When you have a chance to charge elsewhere, the Volt makes it quick and easy to override the utility rate programming.

 

[HighRollsVoltDriver]

Who is lying? Me or the energy display?

Oh, and it doesn't look like the 'phantom gas' was explained.
It's believed to just be a software 'feature' ("it's not a bug, its a feature!")
In that the computer sees all this power coming from seemingly nowhere, and battery is full. Therefore, must be from gas.
So it will then count gas mileage until you drop back down to normal levels.

This is a "feature" following its own simplified logic. I really have trouble to explain my Volt´s energy display (which is THE KEY DISPLAY to ME in this vehicle) to somebody who is new to the car. Every time! Usually I am at work or down in town after this great software "feature" has done its job cutting a blue slice out of the green pie. I say " I haven´t used any gas today", he/she asks why there are 4 gas miles shown, I say, "well, I honestly don´t know. I just drove down the mountain. Just on battery. But look here, the GAS USED indicator shows ZERO point ZERO." Then the person says, that this would not make any sense. And I agree. And the situation sucks. And we usually both agree that GM makes good cars, but that they have lousy human/machine interface programmers. And bad service. No software update for this issue in 4 years?!?! How ignorant can a company be. But advertising with going up and down Pike´s Peak during testing. Once. Not every day. Have to stop now. Getting angry...

 

[ckl]

This is interesting. I live on a decent sized hill as well and I've calculated that I need about 2.3 - 2.5KW to get home from the bottom of the hill. Anything less than that and I will be running on gas by the time I reach my driveway.

Like a lot of you, on the way down the hill, the Volt stops regenerating at some point. Since it is getting cold now, would it not be a good idea to crank the heat up at this point so that energy is not wasted as the two motors are working against each other?

 

[faganns]

If you want to charge the Volt to 75% and then have it stop charging, you can do it using programming available to you in the Volt already. Read up on how to program the Volt for on peak / off peak utility rates. Assuming you have an L2 charger, you can tell the Volt the off-peak period is between midnight and 2:30 AM. It will charge for 2.5 hours and shut off. If you start with an empty battery, that will be around 75%. Adjust the times as needed to get the charge you want.

When you have a chance to charge elsewhere, the Volt makes it quick and easy to override the utility rate programming.

+1 - Couldnt have said it better myself.

 

[ari_c]

There is an additional buffer, around 2-3% SOC that the Volt will allow the battery to be charged before trying to burn off this excess charge to prevent overcharging the battery. I use this to my advantage. I do not live on top of a hill, but I found a way to charge this buffer by turning on the Volt when it is plugged in with a full charge. Depending on how long the Volt has been sitting with a full charge, I can usually get an extra 0.3 - 0.4 kWh out of my battery. The longer the better. Does not work if it has just finished charging, but if it has been sitting for several hours then it works well. So there are some benefits for even those of us who do not live near a hill.