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Discussion Starter · #1 · (Edited)


The kWh/100 miles data was taken from the monthly OnStar diagnostic reports. Temperature data is from the Washington Post Capital Weather Gang.

All months were 100% EV, except for Jan '12 and Feb '12 where I was a lowly 98.3% and 98.5% EV respectively.

The outlier is Aug '13 with 23 kWh. This was due to the fact that I made a successful run for the top VoltStats achievement of EV Miles in a day and managed 313 EV miles. This skewed that month by 1-2 kWh.

I use my Volt for only local driving, so this is probably a pretty good comparison month to month and shows an interesting look into the effect of temperature on the Volt's efficiency.
 

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Very cool. Thanks for posting. Would be easier to read with a second y-axis.
 

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Discussion Starter · #5 ·
Very cool. Thanks for posting. Would be easier to read with a second y-axis.
Didn't know about a secondary y-axis. Here is what it looks like when I added one.



Excellent data, ari. Thank you!

I've got to move somewhere where the average temps are in the 60-70s :D
Keep in mind, I generally drive without climate control. Sometimes on the weekend when my wife is in the car, and she apparently has certain comfort standards which I clearly lack.
 

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Haha. I'm hovering at about 58 kWh / 100 miles with 81% lifetime electric (136 gallons of gas used). Of course, I have no expectation to be close to ari but I also know I sometimes drive fast and I keep the heater running. Interesting to me is that during the summer months, I seem to get even better than ari, which makes me feel warm and fuzzy inside.

ari, for the weather data did you use average for the day or high recorded? I just used average.

Here's mine for 2013 full year.

 

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Didn't know about a secondary y-axis. Here is what it looks like when I added one.
I think you probably need to manually adjust the limits for each of the y axes, so that both data sets will be fully accentuated.

Great data!
 

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Discussion Starter · #8 ·
I think you probably need to manually adjust the limits for each of the y axes, so that both data sets will be fully accentuated.

Great data!
Third times the charm.

 

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Discussion Starter · #11 ·
Is there any way you could convert this to avg. battery range per month vs temp?
There is nothing that really keeps track of that. However, I know during the warmer months when I have 25 kWh or better, this works out to me almost always having a 50 AER. Based on that I came up with the following formula AER = 1,250 / (kWh/100m)

Formula may need a little tweaking, but it gives an interesting result.



One thing that is obvious, is that I was much more efficient in my driving in year #2 than in year#1. This may be partly due to me having higher PSI in my tires: 48 vs 42.
 

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Thanks for doing that so fast. I am really trying to dive into these numbers for better understanding. If your average is 23kWh for 100 miles (like your best month) wouldn't that require 11.5kWh for 50 miles? Or a better way to calculate 23kWh for 100 = 1kWh for 4.35 miles. 4.35 x 11.49 = 50 miles. I am probably missing something since obviously you've driven enough miles to know that your able to get 50 AER but it seems to achieve the 50 mile mark you would have to be closer to 20kWh for 100 miles for 2012. Again I am not calling you liar I have seen plenty of people achieve 50 or even better.
 

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One thing that is obvious, is that I was much more efficient in my driving in year #2 than in year#1. This may be partly due to me having higher PSI in my tires: 48 vs 42.
Wow. Do you really maintain such a "high" PSI (at least compared to the 38 PSI recommended). I keep mine at 41/42 and get nervous when they go up to 45 PSI when driving longer distances.
 

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Discussion Starter · #14 ·
Thanks for doing that so fast. I am really trying to dive into these numbers for better understanding. If your average is 23kWh for 100 miles (like your best month) wouldn't that require 11.5kWh for 50 miles?
I capped it at 50 since I have a 2012. The calculation for that 23 kWh actually came out to 54. The reason Aug 2013 was so high was I had a number of trips in excess of 65 miles per charge on one day so this really skewed those numbers.

Wow. Do you really maintain such a "high" PSI (at least compared to the 38 PSI recommended). I keep mine at 41/42 and get nervous when they go up to 45 PSI when driving longer distances.
The sidewall maximum I think is 51 and I have not had any issues with running at 48 PSI except maybe the ride is a bit rougher. The rolling ability of the Volt with 48 PSI is quite amazing. I can notice a huge difference in my neighborhood alone. I actually shift to N quite frequently on downhills to gain the maximum rolling speed.
 

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Ari,

Can you explain where you come up with 54 AER? At 23kWh/100miles?

And I understand the numbers are skewed just using the 23kWh as an example.
 

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Discussion Starter · #16 ·
Ari,

Can you explain where you come up with 54 AER? At 23kWh/100miles?

And I understand the numbers are skewed just using the 23kWh as an example.
Well, I initially used 10 kWh per charge in my calculations.

let's take 25 kWh/100 miles as an example.

With 10kWh per charge this works out to

10kWh / x miles = 25 kWh / 100 miles
1,000 kWh * miles = 25 kWh * x miles
x = 40 miles

Now this is not right. There about a 20-30% loss so assuming that 25 kWh/100 miles = 50 miles range works out to 12.5 kWh

Using 12.5 kWh for a full charge with 23 kWh / 100 miles works out to 54.35 miles.
 

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Your example is exactly how i was calculating it and it was what i was getting at. I thought a 2012 shows about 10kWh for a full charge energy information info.

Sorry to be such a pain but what do you mean 20-30% loss?

Are we actually using closer to 12.5kWh for a full charge?
 

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Discussion Starter · #18 ·
Your example is exactly how i was calculating it and it was what i was getting at. I thought a 2012 shows about 10kWh for a full charge energy information info.

Sorry to be such a pain but what do you mean 20-30% loss?

Are we actually using closer to 12.5kWh for a full charge?
The loss is in the AC to DC conversion when charging. I assume the number for kWh used is based off of electricity used to charge the Volt and not the amount used by the Volt. I could be wrong, but the numbers seem to indicate the charging loss is included in the numbers.
 

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I took your data and plotted it on an X-Y chart. I think it helps clarify the relationship between temperature and kWh/100m.



One interesting thing to note: There are 5 points that seem to be off the bottom of the general trend [(42.3,30), (46.6,27), (62.4,25), (71.3,25) and (77.1,23)]. Those points happen to be the last five points in the original chart. So your efficiency improved over the years, perhaps as things broke in better...? Or maybe you drive more conservatively as you age!

A couple of other comments: If you used any heat on those cold days, it affects the results. And second, here in Phoenix range decreases a lot more in the summer than in the winter as air conditioning is a necessity in the summer while heat is only a luxury in the winter.
 

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So I think what your saying is that OnStar Reports the Usage as AC Watts. And the car reports off of DC watts.

So when trying to compute how much the cost to recharge a completely drained 2013 I should be using ~10.8kWh x 1.20% (or roughly)? And than multiply that by what I am paying the Electric company per kWh?
 
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