[heyeph]

I have had only two situations where I exceeded my EV range and started using gas. In both cases, I was driving on the highway and I was surprised to see that, despite regen occurring, I never went back into EV mode.

If I was driving in stop/go, non-highway situations, would I ever regen enough to pop back into EV mode without recharging?

 

[ClarksonCote]

I think you're referring to counting "electric miles" as "EV Mode"

In that case, it will not go back into "EV mode" but it will turn of the engine occasionally and use electric power captured from regen to propel the car. In stop and go traffic, its quite possible to have the engine off much more frequently than having the engine on.

However, counting miles as electric implies the energy came from the grid. Once the battery has run out of its initial charge, all subsequent energy is derived from gasoline (including energy from regen). So while the engine will turn off for periods after enough regen etc., it will correctly count these miles as "gas miles" since the energy came from gasoline. After the battery has depleted, this is analogous to a normal hybrid car without a plug, that has its engine turn off sometimes but the energy still came from gasoline.

As an aside, Ford considers any mile that the engine is not running as "EV miles" on their plug-ins, even if their original battery charge has depleted, and that is very misleading. I believe they're the only ones that do this and, truthfully, I'm surprised they haven't been sued for deception.

 

[heyeph]

Why is energy created from regen (braking, coasting, etc.) considered sourced from gasoline? Doesn't make sense to me.

 

[Barry]

If you accelerate using gas, then convert that speed to electricity through regenerative braking, the electricity was generated using gas as the original fuel.

The only energy counted for your EV miles is energy that comes from the grid. Actually, there are ways to fool it, but that is the general idea.

 

[flyingsherpa]

Why is energy created from regen (braking, coasting, etc.) considered sourced from gasoline? Doesn't make sense to me.

Where did the energy come from in the first place? Hint: gasoline.

If you are in CS mode, the ICE is what is ultimately supplying all the energy. So if you're going 70 mph on the highway, and regen anything back into the battery, those are gas-sourced watt-hours, and the Volt's computers tallies them as such.

You could maybe argue this unfair if you are at the top of Mt. Washington and the just car switched to CS mode at the peak. You can regen over half the pack on the way down, and it's inaccurate to count those as gas miles (they came from gravitational potential, and the potential came from grid-kWh on the way up), but the car will because it isn't terrain-aware like that.

 

[caskConditionedAle]

would I ever regen enough to pop back into EV mode without recharging?

This is possible, sort of... I exhausted my battery driving up Mt. Washington. On the way down, I regen-ed enough for about 15 miles of driving. At the bottom, I pulled over, turned the car off, then turned it back on. Now I was in EV mode without recharging.

 

[wordptom]

As an aside, Ford considers any mile that the engine is not running as "EV miles" on their plug-ins, even if their original battery charge has depleted, and that is very misleading. I believe they're the only ones that do this and, truthfully, I'm surprised they haven't been sued for deception.

The usage screen displays electric vs gas miles, not battery miles vs ICE is running miles. In terms of AER and MPGcs stats, those can’t be influenced much after the battery is fully depleted.

Perhaps Ford’s use of counting all battery miles as EV miles helps redirect driving techniques from statistics management to ICE-time management (i.e., if Volt displayed battery vs ICE is Running miles, you should get the same battery miles/kWh Used numbers for comparison with other electric cars, you just couldn’t monitor the kWh Used and AER per full charge numbers unless you fully depleted the battery prior to any ICE use).

Drive down a long steep hill with a fully depleted battery, and when you reach level ground, you have regen power in the battery you can use to drive for several miles. Does it matter to you, except for stats purposes, if those distances are counted as Electric or Gas miles? Because your battery was out of grid power and thus "fully depleted," the distances count as Gas Miles, and once the regen power is depleted, the ICE will start again.

Drive down the same hill in Hold mode, and the distances also count as Gas miles. Switch from Hold to Normal instead before heading down, and the distances count as Electric miles. No operational difference, but the mode choice influences the AER and MPGcs stats.

Or, with a fully depleted battery, switch to Mountain Mode, continue driving for ~10 minutes (Gen 2, ~20 minutes for Gen 1), switch back to Normal, and you’ll have ~2 bars (~4 bars for Gen 1) of power to fuel the primary electric motor for the price of the small amount of gas needed to generate that recharged power. Continue driving using that MM-recharged-from-full depletion power and most Volts will count the distances as Gas Miles. If you stop the car and turn it off and back on again after MM recharging, 2011/2012 Volts (and perhaps later models) will count the distances as Electric Miles. Does it matter, except as it influences the AER and MPGcs stats?

 

[RePo]

Say, for the sake of argument, that regenerative braking is 100% efficient (it is not). You're driving on gas at 40 mph. You regen to a stop. That momentum was captured in the battery. Now you start out again and accelerate back to 40 mph without engine start, using the power you just stored in the battery. That energy is quickly used up, in about the same amount of time you spend creating it (braking).

You'll never regen brake a few times for a few hundred feet, and then go on driving for miles on those few electrons recovered. Due to losses the power saved won't even take you as far as the distance your traveled while regenerating it.

 

[Loboc]

Pretty much answered well in the above comments. My 2c: don't worry about it. Volt counts the way it counts and without being GM programmers, we can't change it.

Heck, it calculates mpg by dividing miles by gasoline only. No acknowledgement in that calculation the machine actually went 50+ miles on electricity. So, I get 80mpg (or 600mpg). Yeah right. Energy is energy. At least add them together first.

I use an external program to calculate $pm. MPG is meaningless @ anything over 100 while $1.17/mile makes sense. (Add up the car's cost/month, insurance, fuel, electricity, car washes, fluids, and everything else then divide by miles those dollars went.) It's called TCO. Total Cost of Ownership. If people looked at those numbers, they probably wouldn't buy a car. Much less an expensive car.

 

[Raymondjram]

Why is energy created from regen (braking, coasting, etc.) considered sourced from gasoline? Doesn't make sense to me.

It does if you didn't recharge the battery with an EVSE from a power outlet. The energy from the gas engine in a hybrid (such as in the Volt) powers the wheels (chemical to thermal to mechanical) and the excess charges the battery (mechanical to electrical). Then when the brakes are first applied, the motor becomes a generator, and converts the kinetic energy (momentum) from mechanical to electrical and charges the battery. So if you never charge externally, ALL the energy you ever use in the Volt will be from the gasoline your burned first.

 

[DZD]

Wow - learned a lot from this thread - one of the things that impresses me about the Volt is when the battery is depleted, it will switch over to ICE - but as the battery is charged it will start using the battery again - I reset Trip B when my Volt switches to ICE and find that the MPG goes up because of this.

I've never really watched the gas miles vs battery miles - but my initial expectation would be that gas miles should only show when the gas engine is running. I know I'll lose that argument with a lot of you. It doesn't matter to me if ICE charged the batter or not - it's battery miles vs. ICE miles.

Shout out to the guy who regen'ed a lot - then turned the car off and back on - way to get back into EV mode!

 

[quirkySquirt]

For those of you that actually charged the battery from a prolonged descent down a mountain or hill, what were you averaging for the charging rate? 40 kW? 100 kW? And there were no ill effects? I can understand the battery back and charging system accepting a few seconds of max regen at 100 kW, but would the battery and/or charging system handle sustained 40+ kW being dumped into the battery with no ill effects?

 

[alfon]

I would imagine the Volt's electrical charging system has been designed for such an event. There are probably many owners in this forum who drive down long mountain grades for miles and dumped 15-40 KW of energy into the battery with no ill effects after thousands of miles. Perhaps they may be able to comment on this post.

 

[quirkySquirt]

That makes sense. And thank you for specifying the correct regen range. I have no idea why I took the max acceleration power consumption and used it for regen. Can you imagine 100 kW of regen? The braking feat to accomplish that (if possible)? Hilariously frightening I imagine.

 

[wordptom]

Seems to me the recharging rate of downhill braking regeneration would be proportional to the steepness and speed of the descent. Could you even descend far and fast enough to regen 10-14 kWh of power back into an empty battery at a recharging rate that might affect battery longevity (see caskConditionedAle’s post above of obtaining only ~15 miles of regen after descending Mt. Washington)? I suspect there are only a limited number of driving locations that include a descent long and steep enough to fully recharge a fully depleted battery via regeneration (e.g., from the top of Pike’s Peak?). Regen concerns are more often expressed by those who live at the top of a hill and recharge overnight who are concerned about adding excess regen to a fully charged battery during the next morning’s descent. Once the regen fills the available small buffer above the "fully charged" soc, the system shifts to other methods of handling the downhill momentum. This limits the length of time any regen charging would be in effect. I suspect GM frowns upon recharging the battery by towing the car to capture regen.

As for the other fast-charging method we have for the Volt, Mountain Mode, the Self Charging Chevy Volt video shows a 2012 Volt using MM to recharge a fully depleted battery to the MM-maintained level (45%, according to Wikipedia) in ~15 minutes, using 0.36 gallons of gas. The Volt in the video is being MM recharged while parked, but there’s no reason to think it takes longer if done while driving down the road under moderate load conditions. At this rate of charge, MM could fully recharge a fully depleted 2012 Volt battery in ~ 34 minutes (or about 8 times faster than L2 charging).

I suspect MM recharging speed has little impact on battery life, as it is rarely used as the primary means of keeping a charge in the battery. Under moderate driving conditions it operates for only ~15 minutes for a Gen 1, about half that time for a Gen 2, even less if the battery is only partially depleted. The size of the MM-maintained buffer is related to the maximum amount of additional battery power GM determined might be needed to maintain performance when the car was being driven in Range Extending mode in an environment requiring high power demands, such as when trying to pass while driving at freeway limits up steep hills. GM limited the recharging capability to the MM-maintained buffer level most likely because the cost of gas used to recharge with MM is generally more expensive than the cost of grid electricity from the wall needed to recharge the battery to the same level.

 

[hellsop]

Seems to me the recharging rate of downhill braking regeneration would be proportional to the steepness and speed of the descent. Could you even descend far and fast enough to regen 10-14 kWh of power back into an empty battery at a recharging rate that might affect battery longevity (see caskConditionedAle’s post above of obtaining only ~15 miles of regen after descending Mt. Washington)? I suspect there are only a limited number of driving locations that include a descent long and steep enough to fully recharge a fully depleted battery via regeneration (e.g., from the top of Pike’s Peak?). Regen concerns are more often expressed by those who live at the top of a hill and recharge overnight who are concerned about adding excess regen to a fully charged battery during the next morning’s descent. Once the regen fills the available small buffer above the "fully charged" soc, the system shifts to other methods of handling the downhill momentum. This limits the length of time any regen charging would be in effect. I suspect GM frowns upon recharging the battery by towing the car to capture regen.

As demonstrated in the results reported here: http://gm-volt.com/forum/archive/index.php/t-141178.html

which I'm reading as 1) "Yes, once the battery is full, the car 'turns on' the gas engine to supply retarder power, to keep up the 'regen' effect, but may be mostly just using the clutches to spin the engine and give some actual physical compression braking to the system". This is a poorly explored area of behavior and even less documented outside GM. It does seem like there's VERY little headroom, though, on the charge beyond "full" that the battery is allowed to go. Maybe a half a kwh. 2) Climbing looks like it costs about and extra 1 kwh per 750 feet of ascent and gains 1 kwh per 900-ish feet of descent compared to travelling the same distance on the flat. This compares pretty well with the estimates referred to in one of the urls referred to in the archive thread that saw "1.5 kwh per 1000 feet up, 1 kwh per 1000 feet down" ballparked over three different EVs.

 

[heyeph]

As for the other fast-charging method we have for the Volt, Mountain Mode, the Self Charging Chevy Volt video shows a 2012 Volt using MM to recharge a fully depleted battery to the MM-maintained level (45%, according to Wikipedia) in ~15 minutes, using 0.36 gallons of gas. The Volt in the video is being MM recharged while parked, but there’s no reason to think it takes longer if done while driving down the road under moderate load conditions. At this rate of charge, MM could fully recharge a fully depleted 2012 Volt battery in ~ 34 minutes (or about 8 times faster than L2 charging).

This is fascinating. So, this could get you back in EV mode faster at the expense of using more gas?

 

[wordptom]

This is fascinating. So, this could get you back in EV mode faster at the expense of using more gas?

If your goal is to fuel the primary traction motor from the battery instead of the output of a gas-generator, then yes. MM partially recharges a depleted battery much faster than stopping the car to plug into the grid.

Note that Gen 1 Volts have a ~4 bar MM buffer, whereas Gen 2s have only a ~2 bar buffer (~9 ev miles, whoopee!) because their gas engine is more powerful, so fewer circumstances when that MM battery buffer power may be needed to maintain performance.

The distance you can drive on that MM-recharged power is just about the same distance as you can drive using the same amount of gas to generate electricity "on the fly" to fuel the traction motor (Gen 2 CS operations are more likely to use some of that gas as propulsion fuel instead of as generator fuel), it’s just usually a more expensive method of recharging. When you MM-recharge while the car is moving, this extra gas consumption makes the Gas Used numbers increase faster than in normal Range Extending mode, giving the appearance your mileage is decreasing, but it’s gained back when the MM-recharged power is used and counted as Gas Miles.

You still won’t return "officially" to EV mode, because that’s defined for stats purposes as using grid electricity stored in the battery. Using MM-recharged power can mess up your driving stats. MM-recharged miles should count as Gas Miles, created by running the ICE. When switched to MM before full depletion, then back to Normal after MM-recharging, 2011/2012 Volts would immediately start counting them as Electric Miles. That glitch was modified to count them properly as Gas Miles starting with the 2013 model, but any model, apparently, might do the same if you turn the car off and then back on again after MM-recharging. Not including these MM-recharged miles in your Gas Miles total lowers your MPGcs gas mileage (fewer total gas miles on same amount of gas used). And even if those MM-recharged miles are counting up as Electric Miles, your kWh Used number will not change until that power has been used up. Because of this "glitch," I once ended a trip in my 2012 Volt with the usage display reading ~90 Electric Miles and 9.8 kWh Used.

 

[AE7HF]

If you get out and push fast enough, you can reclaim some energy without using the ICE

 

[gen2north]

This is possible, sort of... I exhausted my battery driving up Mt. Washington. On the way down, I regen-ed enough for about 15 miles of driving. At the bottom, I pulled over, turned the car off, then turned it back on. Now I was in EV mode without recharging.

I've experienced the same when driving into the mountains around Anchorage. I've been able to get 5 or more miles when carefully coming down the hillside as to maximize regen.