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Discussion Starter #1
I've only had the Volt for a few weeks and on a drive this morning up and down a mountainous windy road, I noticed that the kWh used that is reported on the dash decreased as I was using the regenerative brakes on a decline. I was driving is Sports mode and L gear. This is interesting but makes for inaccurate miles/KWh estimations. Of course, the LEAF reports miles/kWh but not total KwH used.

Has anyone else noticed this?
 

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Why do you feel that makes the estimate inaccurate? The Volt recaptures that energy and uses it to propel the car further. Tracking that makes the kWh/mile accurate. If it didn't do that, the kWh/mile would always be higher than reality.
 

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Seems to make sense to me. When you're going down hill and the Volt is in regen, it's charging the battery, or essentially "putting gas back in the tank."

Assume for a moment that you started with a fully charged Volt, and drove it up a hill. At the top of the hill it reads 2 kWh used. Then you drive it back down the hill, and regen charges the battery back to full. As a result you've driven X miles and used 0 kWh (of course this would never happen in reality because you'd never recover as much power coming down as it took to drive up)
 

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Discussion Starter #4
Why do you feel that makes the estimate inaccurate? The Volt recaptures that energy and uses it to propel the car further. Tracking that makes the kWh/mile accurate. If it didn't do that, the kWh/mile would always be higher than reality.
I think that the kWh that's regenerated should increase the DTE estimate on the odometer but that the total kWh used should reflect how much I really use both what I started with and what I was able to recapture. No?
 

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Discussion Starter #5 (Edited)
Seems to make sense to me. When you're going down hill and the Volt is in regen, it's charging the battery, or essentially "putting gas back in the tank."
I see what you mean but if I drive and used up say 9.5 kWh and then recharge for a few hours but use it again before it's full, the total kWh reported can be more than the max 10.4 per charge (I've seen 12.5). Anyway, why should kWh used when I charge from an outlet be treated differently the those that I get from regenerative braking?
 

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kwh and regen

the only part of the system i don;t like is the MPG pegged at 250+ and the miles to empty pegged at 50 miles.

I see this every day, because i start 1500' vertically above where i end up on my commute. i start with about 45 miles range and a full battery. even with a full battery, the battery takes a little more charge, because i still get regen most of the way down the hil. finally, when the battery just can't take any more, the regen cuts out and i have to brake the rest of the way. I have to drive several miles before the battery meter or the 50mile range start to decrease.

interestingly, since my 30 mile commute starts high and ends low, I get what seems to be amazing range-- about 30 miles using about 3kw/h. but on the way back, my full charge barely gets me home, due to that 1500' hill at the very end. i use 40% of my battery on the last 6 miles of my drive.
 

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I see what you mean but if I drive and used up say 9.5 kWh and then recharge for a few hours but use it again before it's full, the total kWh reported can be more than the max 10.4 per charge (I've seen 12.5). Anyway, why should kWh used when I charge from an outlet be treated differently the those that I get from regenerative braking?
Because regenerative braking energy is recapturing the original charge. You'd be counting some of the charge you put in the battery twice, which would be wrong.
 

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Discussion Starter #8 (Edited)
the only part of the system i don;t like is the MPG pegged at 250+ and the miles to empty pegged at 50 miles.

I see this every day, because i start 1500' vertically above where i end up on my commute. i start with about 45 miles range and a full battery. even with a full battery, the battery takes a little more charge, because i still get regen most of the way down the hil. finally, when the battery just can't take any more, the regen cuts out and i have to brake the rest of the way. I have to drive several miles before the battery meter or the 50mile range start to decrease.
I don't understand those limitations either though for a car that's supposed to do 37 miles EV, getting 50 miles is really cool. Some people over at the LEAF forum who live on mountains will start off in the morning with 80% charge and get to the bottom with a 100% charge. I suppose if you did this you can get the regenerative braking and save the regular brakes ;-)
 

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I think that the kWh that's regenerated should increase the DTE estimate on the odometer but that the total kWh used should reflect how much I really use both what I started with and what I was able to recapture. No?
What you effectively use is being calculated right and gives you accurate kWh/mile.

Look at it this way: The Toyota Prius gets 50mpg by recapturing energy during braking with its batteries too. Should the MPG figure be lower and not include the fact that it can recapture this energy? Because, without recapturing this energy the MPG would not be as high.
 

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I own a 2011 so I do not have the Total kWh value displayed.

My first reaction to all this when 2012s came out with this is that it was 'wrong' and conflicted with the battery milage display. I realize it was just a design decision to both make it consistent for everyone and representing External [grid/solar/etc] supplied Total kWh.

I try to think of it as two virtual batteries - 1) externally charged batt kWhs. (ECBk) and 2) regen charged batt kWhs (RCBk). When you regen they charge up #2 - RCBk. The RCBk gets used/drained first and that kWh counter goes to the "bit bucket". The ECBk then gets used second and that kWh counter go toward Total kWh.

I don't know/recall if there is a third virtual battery - 3) ICE generator charged batt kWhs (IGCBk).

Interesting point about the miles/kWh. They would need to be consistent it would seem (ECBm)/(ECBk) or (ECBm+RCBm)/(ECBk+RCBk) [where m is miles).

[Hope that makes some sense as I spent all day coding and wrapping up a project before taking tomorrow off work]

Because regenerative braking energy is recapturing the original charge. You'd be counting some of the charge you put in the battery twice, which would be wrong.
I don't really follow this. Imagine you live on top of a hill and forgot to plug your car in. In the morning you use regen braking to go down the hill and get 1 kWh of energy. You then drive 5 miles using that 1 kWh of energy. There is no original charge.

I don't understand those limitations either though for a car that's supposed to do 37 miles EV, getting 50 miles is really cool. Some people over at the LEAF forum who live on mountains will start off in the morning with 80% charge and get to the bottom with a 100% charge. I suppose if you did this you can get the regenerative braking and save the regular brakes ;-)
If you are implying that the 13 miles comes from regen braking I think that is not quite true. You can drive at a modest and steady speed in 70F degree weather and go 50 EV miles. True if you are in stop and go you will get some "regen miles".

What you effectively use is being calculated right and gives you accurate kWh/mile.

Look at it this way: The Toyota Prius gets 50mpg by recapturing energy during braking with its batteries too. Should the MPG figure be lower and not include the fact that it can recapture this energy? Because, without recapturing this energy the MPG would not be as high.
Very interesting point and would be true in stop and go. I think they claim 50 MPG driving down the road at 55-ish-MPH.
 

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The only number that really counts is the one that is displayed when you stop. At that point the KWH's used is simply what you had when you started minus what you have left when you stopped.

It is crazy to try to calculate KWH's generated by regen. If you used 10 KWH for the trip it is or relevant if you actually used 12 KWH and got an additional 2 KWH from regen. At the end of the trip you still have 10 KWH less than when you started, and that is what you will have to pay on your electric bill.

On those days where you took more than one trip and used more than 10 KWH, the total KWH is still the amount you will have to pay for on your electric bill...
 

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I don't really follow this. Imagine you live on top of a hill and forgot to plug your car in. In the morning you use regen braking to go down the hill and get 1 kWh of energy. You then drive 5 miles using that 1 kWh of energy. There is no original charge. 50 MPG driving down the road at 55-ish-MPH.
How did you get to the top of the hill?
 

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Discussion Starter #14
If you used 10 KWH for the trip it is or relevant if you actually used 12 KWH and got an additional 2 KWH from regen. At the end of the trip you still have 10 KWH less than when you started, and that is what you will have to pay the utility to recharge the Volt back to 100%.
Hmm, interesting thought and it echos what ItsNotAboutTheMoney said about counting things twice but I dunno, I'd still like to know how much energy was used. Scottf200's explanation gives a reasonable explanation about the decision made to report it the way it is.
 

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Hmm, interesting thought and it echos what ItsNotAboutTheMoney said about counting things twice but I dunno, I'd still like to know how much energy was used. Scottf200's explanation gives a reasonable explanation about the decision made to report it the way it is.
It isn't just about the money, it is about the environmental impact. If you have to put 10KWH of electricity from the utility into the Volt, that is also the environmental impact.. If you used 12 KWH and generated 2 from regen, your environmental impact is 10 KWH not 12 KWH.
 

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The miles/kWh on the Leaf (I saw you post over there too), includes subtracting back the kWh from regeneration so the Leaf and the Volt both treat it the same way. Total miles driven, total kWh used. If the Leaf had a kWh used display you would see it go backwards too. Instead you just see the miles/kWh go up faster since the kWh number is decreasing.

I guess it might be interesting to know what the miles/kWh would be without regeneration as an intellectual exercise or to better understand the characteristics of the electric motor but the bottom line to me is how many kWh did I pay to put in, how many miles did I get for my money.
 

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Discussion Starter #17
It isn't just about the money, it is about the environmental impact. If you have to put 10KWH of electricity from the utility into the Volt, that is also the environmental impact.. If you used 12 KWH and generated 2 from regen, your environmental impact is 10 KWH not 12 KWH.
Good point about the environmental impact; I suppose I'd just like to know the work (in physical terms) that was done - i.e. the force and energy expended to move the Volt and passengers a certain distance.
 

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Good point about the environmental impact; I suppose I'd just like to know the work (in physical terms) that was done - i.e. the force and energy expended to move the Volt and passengers a certain distance.
I can see the intellectual curiosity being an engineer...

I'm curious if the Volt has the capability to measure the amount of regeneration. Where would it be measured?

Total KWH used would appear to be easier to measure, as it is a simple calculation of the battery SOC before and after.
 

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I suppose I'd just like to know ... the force and energy expended to move the Volt and passengers a certain distance.
What they're trying to explain is this is exactly what you are getting. Assume you are going from Point A to Point B to Point C. Point B is at the top of a hill. Point A and Point C are in valleys. You use 5 kWh to go from Point A to Point B. Then you gain through regen 2 kWh going from Point B to Point C. How many kWh have you used going from Point A to Point C? The answer would be 5 kWh - 2 kWh = 3 kWh.
 

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How did you get to the top of the hill?
What they're trying to explain is this is exactly what you are getting. Assume you are going from Point A to Point B to Point C. Point B is at the top of a hill. Point A and Point C are in valleys. You use 5 kWh to go from Point A to Point B. Then you gain through regen 2 kWh going from Point B to Point C. How many kWh have you used going from Point A to Point C? The answer would be 5 kWh - 2 kWh = 3 kWh.
This makes sense. Even if I paid $0.10/kWh for those initial 5 kWhs ($0.50) and used them all up by the time I got to the fancy restaurant on the top of the hill with my friend (Volt) ... I was still given back $0.20 by my friend (Volt) for giving him a ride down the hill so I'm still only out $0.30 overall.
 
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