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Hey everyone,
My wife recently went on a 400 mile trip. Inadvertently she used all of her battery power early in the trip and did the latter part of the trip all on ICE. At the end of the trip there was a 30 mlle downhill where she lost altitude from 4500ft to 500ft.

I was surprised that she reports she got no bars of battery power back given the long down hill section. Wouldn't the car be regenerating at every little junk of deceleration and then for that long down hill?

DD
 

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Basically, this is dependent upon the speed at which she was driving.

So in 30 miles, she dropped 4000 feet in altitude or about 133 ft per mile.

There is a nearby hill that has about a 400 foot drop, but it is only about one mile long. When I descend this hill in my 2016 Volt, at 35 mph (speed limit is 30 mph), I can regen about 0.3 kW, or 0.1 kW for every 133 feet of altitude drop.

But remember, at 35 mph, the Volt only needs about 4 kW of power to drive the vehicle. Therefore, the gravitational forces exceed the drag forces and there is the opportunity for regen.

I tried this same type of drive on an interstate highway at 70 mph, and got basically zero regen. That's because the drag forces at 70 mph (nominal 20 kW) were greater than the gravitational forces.

I like to think of it this way; for any hill, depending on the slope, there is a terminal velocity at which your car will coast with no energy input. Obviously, the steeper the hill, the higher the terminal velocity. If your speed is less than this terminal velocity, there is an opportunity for regen. However, if your speed exceeds this terminal velocity, your car will need added energy input to maintain the higher velocity.
 

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Basically, this is dependent upon the speed at which she was driving.

So in 30 miles, she dropped 4000 feet in altitude or about 133 ft per mile.

There is a nearby hill that has about a 400 foot drop, but it is only about one mile long. When I descend this hill in my 2016 Volt, at 35 mph (speed limit is 30 mph), I can regen about 0.3 kW, or 0.1 kW for every 133 feet of altitude drop.

But remember, at 35 mph, the Volt only needs about 4 kW of power to drive the vehicle. Therefore, the gravitational forces exceed the drag forces and there is the opportunity for regen.

I tried this same type of drive on an interstate highway at 70 mph, and got basically zero regen. That's because the drag forces at 70 mph (nominal 20 kW) were greater than the gravitational forces.

I like to think of it this way; for any hill, depending on the slope, there is a terminal velocity at which your car will coast with no energy input. Obviously, the steeper the hill, the higher the terminal velocity. If your speed is less than this terminal velocity, there is an opportunity for regen. However, if your speed exceeds this terminal velocity, your car will need added energy input to maintain the higher velocity.
Well said.
 

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Once the Volt depletes the batteries and shifts to ICE mode all regenerated energy is counted as ICE energy, not EV energy. Even though the energy is stored in the batteries it is still counted as ICE energy. It is reflected in improved ICE mpg numbers however.

VIN # B0985
 

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Yes, it will be regenerating every time the car slows down and when going down hills where the car would otherwise speed up.

In addition to BillR's detailed answer about how much regen you get on freeways, keep in mind that the Volt tries to account regenerated energy based on the initial source - so energy gained going down hill on gas will be counted as gas miles/energy, and will be folded back in by cycling the engine off more or running it at lower rpms rather than saved as future electric charge.

Without OBDII instrumentation, you'll only see that regenerated energy if it becomes enough in a single cycle to push you up a whole bar, which takes quite a descent. (You'll see that it is happening on the power flow and power gauge, just not where the energy is going.
 

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What your wife did get was much better gas MPG. The Volt did regen but it needed all the extra power to maintain speed. What it didn't have to do was run the ICE as hard.
 

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Have no fear, the regen'd electric was not wasted. The main display in front of you will not reflect large regen'd power. In the Gen 1 Volt, you could see this shown in the energy distribution display. That display has a big horizontal battery that would increase the number of green bars even after you are in CS mode.

On my Gen 2, I don't play around with the displays as much as I did on my Gen 1, I'm sure somebody can confirm if Gen 2 does display this.
 

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All good answers. In a nutshell, it needs to be steeper. Also be aware that the car is not trying to save this energy to boost the battery charge level. The engine shuts down and all the stored energy will be used up. Either during the descent or after she reaches the bottom and continues driving home. I think some owners have reported getting their battery more than half charged driving down Mt. Washington or Pikes Peak.
 

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If you want to save the charge to run in battery only mode later, switch to mountain mode before your descent. That will use the power to recharge the battery up to the limit of mountain mode (maybe more I haven't been able to test this). You would have to shut the car off to get it back into battery mode, because the car has determined that "normal" means the battery is dead unless you reboot the system.

Not that any of that is worth the effort, no matter what you do you won't be wasting the electricity generated.

FWIW - to me, the ability to go down long hills without using the brakes is a bigger benefit than the extra electricity. All cars should have that feature at minimum (in a few years all Volvo's will)
 

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All cars should have that feature at minimum (in a few years all Volvo's will)
True, as long as they have a battery with enough capacity to hold all the recovered energy. When the battery is full, there is no where to put additional energy. I've experienced that with Gen2 Prius. Your regenerating along then all of a sudden you are free wheeling when the battery fills up. The Gen1 Volt handles this by working the 2 motors against each other (probably generating heat as a result).

VIN # B0985
 

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Once the Volt depletes the batteries and shifts to ICE mode all regenerated energy is counted as ICE energy, not EV energy. Even though the energy is stored in the batteries it is still counted as ICE energy. It is reflected in improved ICE mpg numbers however.

VIN # B0985
What AZ said. simple, to the point and correct.
 

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I was surprised that she reports she got no bars of battery power back given the long down hill section. Wouldn't the car be regenerating at every little junk of deceleration and then for that long down hill?

DD
Regenerative braking was designed as an alternative to friction braking for electric cars. That it also recharges the battery is a bonus, but it’s called regenerative braking, not regenerative refueling. Braking is performed in all modes of driving, and the use of that regen increases the efficiency of the driving mode under which it was created.

Regen doesn’t care if you’re in Electric Mode or in Extended Range Mode. Your wife very likely obtained some downhill regen while going down the long downhill section, but because the battery was out of grid power, all the "electric" miles were already used up, so when the downhill regen was then used to "drive on battery power," the distances counted as Gas Miles.

The Volt’s energy usage screen identifies distances driven on grid electricity as "electric" miles and distances driven on gas-generated electricity as "gas" miles. Not all "battery-powered" miles are Electric Miles. If you’re driving on grid electricity and get some regen, the regen battery miles will count as Electric Miles. If you’re driving in Extended Range Mode and get some regen, the regen battery miles will count as Gas Miles. If your battery is fully depleted, you have no more grid power until you plug into the wall, and all of the miles driven on the battery power put there by regen will be Gas Miles.

If you get some regen while in Extended Range Mode (or use Mountain Mode to recharge to the MM-maintained level) and then turn your Volt off and back on again just to get the battery power to count as Electric Miles, you are corrupting your stats. The miles may be counted as Electric, but your kWh Used number won’t change as it’s used, which artificially inflates the miles/kWh ev mileage numbers, and, by not counting those Extended Range regen battery miles as Gas Miles, your MPGcs gas mileage is reduced.
 

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True, as long as they have a battery with enough capacity to hold all the recovered energy. When the battery is full, there is no where to put additional energy. I've experienced that with Gen2 Prius. Your regenerating along then all of a sudden you are free wheeling when the battery fills up. The Gen1 Volt handles this by working the 2 motors against each other (probably generating heat as a result).

VIN # B0985
That lack of regen can happen on a Bolt too. Usually I turn on Hilltop Reserve so it does not fill the battery completely, otherwise the first 10-15 miles have either zero or limited regen. I only turn it off if we are planning a long trip.

Nothing quite like expecting massive slowing due to regen, only to have minimal slowing, eh? Shoots the "one pedal driving" right down...
 

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If you get some regen while in Extended Range Mode (or use Mountain Mode to recharge to the MM-maintained level) and then turn your Volt off and back on again just to get the battery power to count as Electric Miles, you are corrupting your stats. The miles may be counted as Electric, but your kWh Used number won’t change as it’s used, which artificially inflates the miles/kWh ev mileage numbers, and, by not counting those Extended Range regen battery miles as Gas Miles, your MPGcs gas mileage is reduced.
There are other ways to get the regen power mis-applied to the statistics, especially in hill country or mountains. This is why the MPGe number was created, to provide an "uniform" method for calculating overall efficiency for hybrids (traditional and plug in).
 
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