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I'm currently the owner of a 2012 Volt with 52K miles that I bought in June of 2018 (37k on the battery). The battery would consistently use 9.6 kWh per charge all summer and fall and return 35-40 miles per charge. Since winter came around that mileage has dropped to around 20-24 miles per charge but I've noticed on some days, more so recently that mileage will drop into the teens. I've also noticed that my energy usage has dropped into the mid 8 kWhs and even sometimes as low as 8.0 kWh. This seems to be amplified if I charge the car fully, unplug at 10pm, drive to work at 6am and notice the final energy usage being lower at 7am when I arrive to work.

My question is, is this a battery issue or is it just a winter issue? Does the volt drain the battery overnight if it does not remained plugged in to keep the battery warm? I was under the impression that my energy display should read 9.6 kWhs every time I charge the car fully.
 

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I understand the loss in range in the winter time, I was used to that. I the month of December my energy usage would be 9.6 kWh and an all electric mileage of 20-25. My energy usage now is much less than 9.6 kWh, more like 8.0-8.6 with similar temperatures that were seen in December. My all electric range has dropped more as it appears that the battery may be taking on less charge. Just trying to see if anyone else experienced this specific case.
 

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The start of day, full charge in a 2012 Volt is indicated by ten green bars on the battery icon. The ev range number shown there is the computer’s estimate of how far you may be able to drive if you drive as you usually do on your normal route. How far you can actually drive using those ten green bars on any given day is up to you, your driving habits, the weather, and the driving environment.

Your signature doesn’t include your location, but winter weather can bring a drastic drop in range. The range drop, however, is mostly a product of reduced ev mileage (takes more fuel to drive the same distance in the cold, dense air on wet roads, etc.) and increased cabin heating, rather than a significant drop in kWh per full charge.

The computer takes into account the driving conditions as the state of charge drops toward the "switch to gas" point, so you won’t necessarily get the identical amount of kWh Used out of a full charge every time.

I’m not sure what you mean, however, when you say your energy usage has dropped down as low as 8.0 kWh. If that’s all you see on the energy usage display for kWh Used after driving far enough to fully deplete the battery, something is wrong.

If you are charging at home, I’m not sure why you unplug at night and then depart hours later. Most people, I suspect, normally unplug around departure time. If this is your normal habit, you could press the leaf button after you’ve started the car in the morning to view the energy usage screen on the middle console. Fully charging the car resets this screen to zero, so if battery maintenance has drawn power during the unplugged part of the night, it would show up now as kWh Used. If you keep it plugged in, the car has a chance to draw more from the wall to "top off" the battery and reset it to zero.
 

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This seems to be amplified if I charge the car fully, unplug at 10pm, drive to work at 6am and notice the final energy usage being lower at 7am when I arrive to work.

My question is, is this a battery issue or is it just a winter issue? Does the volt drain the battery overnight if it does not remained plugged in to keep the battery warm? I was under the impression that my energy display should read 9.6 kWhs every time I charge the car fully.
The issue you might be facing is that the TMS runs immediately when you start the car in the morning to warm up the battery, killing your range. I'm not sure if that would be reflected in the kWh used "meter" (which is just an algorithm).

What's the difference when you leave it plugged in so you use the wall power to warm it up instead of the battery? You also might benefit from using departure-based charging so your battery is nice and warm in the morning when you're ready to go.
 

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Here's an example from the most recent instance, I live in the D.C. metro but I was up in PA last week and I was able to charge at a 240V station in a parking garage. I charged the car to full charge at 9pm, unplugged and moved the car to another parking space. At that time only 0.2kWh had been used since the last full charge. I drove to the training location at 8am which was 0.6 miles away and I cant remember the total kWh used at this time. Left at 1pm drove in mountain mode for about 80 miles switched back to normal afterwards. Once my battery was fully depleted it registered a total of 8.0kWh used and an electric mileage of 20.6 miles. Outside air temperatures were in the 20-30 degrees F.

This seems abnormally low to me, any thoughts?
 

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Here's an example from the most recent instance, I live in the D.C. metro but I was up in PA last week and I was able to charge at a 240V station in a parking garage. I charged the car to full charge at 9pm, unplugged and moved the car to another parking space. At that time only 0.2kWh had been used since the last full charge. I drove to the training location at 8am which was 0.6 miles away and I cant remember the total kWh used at this time. Left at 1pm drove in mountain mode for about 80 miles switched back to normal afterwards. Once my battery was fully depleted it registered a total of 8.0kWh used and an electric mileage of 20.6 miles. Outside air temperatures were in the 20-30 degrees F.

This seems abnormally low to me, any thoughts?
I think those kWh are estimates and you are taking them to be exact. Heating the battery takes some kWh. Oil, bearing grease, etc are thicker at 20F and hit efficiencies. As well the battery capacity is temporarily lower in the cold.

I would suggest you read this FAQ to help in your understanding. More FAQs in my sig.

https://gm-volt.com/forum/showthread.php?18609-Battery-Mile-Estimate-in-30-s-not-40-s-50-s.-Problem
 

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Here's an example from the most recent instance, I live in the D.C. metro but I was up in PA last week and I was able to charge at a 240V station in a parking garage. I charged the car to full charge at 9pm, unplugged and moved the car to another parking space. At that time only 0.2kWh had been used since the last full charge. I drove to the training location at 8am which was 0.6 miles away and I cant remember the total kWh used at this time. Left at 1pm drove in mountain mode for about 80 miles switched back to normal afterwards. Once my battery was fully depleted it registered a total of 8.0kWh used and an electric mileage of 20.6 miles. Outside air temperatures were in the 20-30 degrees F.

This seems abnormally low to me, any thoughts?
This has probably been asked before but what is the age of your 12V AGM battery in your 2012 Volt? Also, why did you engage MM when you started on your 80 mile drive. If you had let the Volt's battery fully deplete the Volt would have started CS mode and you would have your total kWh used without adding MM to the equation. Then, if you really want to, you could have switched to MM and the Volt would have built up and maintained state of charge of 4 bars for the remainder of the trip.

When the weather is not quite so cold you might try disconnecting the negative terminal from the Volt's 12V battery and wait a few minutes before reconnecting. This may reset whatever system is responsible for reporting battery usage.
 

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Here's an example from the most recent instance, I live in the D.C. metro but I was up in PA last week and I was able to charge at a 240V station in a parking garage. I charged the car to full charge at 9pm, unplugged and moved the car to another parking space. At that time only 0.2kWh had been used since the last full charge. I drove to the training location at 8am which was 0.6 miles away and I cant remember the total kWh used at this time. Left at 1pm drove in mountain mode for about 80 miles switched back to normal afterwards. Once my battery was fully depleted it registered a total of 8.0kWh used and an electric mileage of 20.6 miles. Outside air temperatures were in the 20-30 degrees F.

This seems abnormally low to me, any thoughts?
You have not observed a lot of information that would help evaluate the issue. Let’s recap:

Fully charged at 9 pm. You don’t mention the estimated full charge ev range. Was it more than 25 miles?

You then unplugged and moved car to another parking spot, by which time the energy usage screen displayed: 0.2 kWh Used.

11 hours later (8 am), you started the car but did not note the ev range estimate upon starting. Has the kWh Used increased beyond 0.2 kWh in the past 11 hours? Has battery maintenance used any power during the past 11 hours?

You then drove to the training location but did not look at the usage screen when you got there. How many kWh were used to drive those 0.6 miles? More than another 0.2-0.3 kWh? Has the ev range estimate changed much from what it read when the car was fully charged?

16 hours after the car was fully charged and then unplugged (a period of time that included parking for ~11 hours, driving less than 1 mile, and then parking for another ~5 hours), you started the car. What was the kWh Used at this point? More than the total amount used to drive~1 mile to work? Any used for battery maintenance?

What was the ev range estimate when you left at ~1 pm? More than 20 miles? You say you then drove 80 miles in Mountain Mode without explaining why you chose to use MM (i.e., were there mountains on your route?), or when you switched to it, or how far you drove after switching back to Normal.

It would be unusual to get only 8.0 kWh Used from a 2012 Volt battery, but at this time of year it might not be unusual to travel only 20.6 miles on 8.0 kWh Used (2.6 miles/kWh). I’ve been driving my 2012 Volt for 6+ years and am currently often hovering between 2.9-3.5 miles/kWh as I drive around Portland in relatively mild winter weather.

Are you sure your Volt switches from MM back into Normal (with the battery icon reappearing with four green bars and the gas pump icon disappearing), or is it possible the Mode switch might have become stuck on Mountain Mode? Being stuck in MM when you arrive home might make you think you had depleted the battery (gas pump icon will still be showing) but had not (and, of course, it becomes unstuck when you turn off the car), and the kWh Used will reflect where it was when you engaged MM.

Do the ev range estimates you see in the morning as you start driving to work reflect the ev miles you can actually drive on a full charge?
 

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A reset (guess-o-meter) may be 35-36 miles and I have not read that only disconnecting the 12 Volt battery will do that function but may.

Only when I had the main battery dropped to add extra metal around the battery have I seen a range reset to the default number.

You can start the Volt after a big temp change and see the number change as you now have a new state of charge even if you used no power.
 

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Have you watched the energy gauge as you drive the car? Is there a point where the EV mileage drops? I recall a post from someone with a battery issue where every morning they had the full 10 bars and by the time they pulled out of the driveway, two bars were gone.

Also - when the car switches over to the ICE, is the EV range 0 or is it switching over before the EV range is fully exhausted? It does seem unusual to get only 8.0 kWh when it should be closer to 10. The winter range will be in the lower 20's though with typical driving.
 

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Hitting 8 kWh used for CS mode represents a problem worth investigating, but we don't know what's causing it--may not be anything to worry about.

The only way to be sure is to do a log. My 2013 had a software bug and it was only revealed after I kept a daily log for a few weeks of kWh used + actual EV range on each full charge to full discharge, along with a few notes of driving characteristics, stops, terrain, temp, etc.

Using Mountain Mode can mess with the kWh used algorithm, so don't make a judgment on that. I've seen on my Gen 2 where I'll get LESS kWh used than expected using Mountain Mode. The algorithm isn't perfect, just software not an actual meter. However, getting far outside the norm means you should take a deeper look and log your results before making a decision. A few one-off events, especially in colder weather, shouldn't be a cause for concern--but a pattern would be a problem.
 

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Been driving my 2014 Volt for several years now, and I'm quite familiar with a range loss in the depths of winter (if that's what you can call it in Central Texas). It used to reliably get 10.5 to 11 kwh until the ICE kicked in. In the last few months, that has dropped to 8.3 to 8.5 kwh which is pretty significant. That's as much as a 25% loss. My driving habits are extremely conservative. I prided myself on routinely getting 50 miles per charge. Now, I am getting 30 - 33 miles per charge. The Chevy dealership won't do anything about it since it has not set off the Check Engine light. When it dropped, I did get a Check Engine light. They put in a software update (as per the recall) and claimed that was problem. However, that recall was for managing the charge in cold weather (based on what I read about it).

Any thoughts on what to do? It seems that, being still under warranty, this should warrant some battery work--perhaps replacing some dead cells.

Anyone have some ideas about how to proceed?
 

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I'm going to let some others chime in, but my recollection is that there was a "fix" for the propulsion power reduced problem in older Volts that permanently reduces the available kWh from the battery pack. I wouldn't call that a fix, personally.

GM has a tool to properly test the individual cells--but it's something the dealer would need to request from GM. I would demand that test be run.
 
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