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Discussion Starter #1
I've recently purchased a second high mileage (136k) 2013 Volt and I noticed a significant range difference between that one and the one I already owned (2013 90k). The range estimate when full on the original one is 44 miles and the higher mileage one is 36. I can make my work commute on the higher range one with distance to spare. The commute is 37.6 miles and I usually have 4 or 5 miles left. On the higher mileage one, I end up running short by a couple miles and use about 2 to 3 miles of the ICE. I was hoping that the new one I purchased just needed some time to get used to the new driving style for the range estimate to creep up but now I'm wondering if there's a battery or some other issue.

I know on the higher mileage one, the lifetime EV miles are about 40k according to Voltstats (39.3 MPGe). I don't know what the lifetime EV miles were on the lower mileage one but I do know the lifetime MPG was roughly 70 when bought so I don't think there's a significant usage difference in the batteries. Both Volts have the front air dam removed and both have non OEM tires. The higher mileage one does have some long lifetime tires with slightly more tread but I wouldn't think that it would cause that drastic of a difference. Is there any test I can do with SPS to confirm the batteries are similar? The one strange thing I found when logging the EV data is that the lower mileage Volt typically uses about 9.2 Kwh during the 37.6 mi commute and the higher one uses 10.1 for the 36 miles it's in EV mode. Does that indicate some loss somewhere?
 

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Well, missing the front air dam and lacking LRRR tires, the cars are both set to be less efficient than they could be. Also, tire pressure? I keep mine at 41psi.
 

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Discussion Starter #3
Agreed about both not being as efficient but they should be similarly handicapped. I actually swapped the larger dam for the smaller one on the original Volt a month or so ago then removed it all together and didn't see much difference. I think speed and traffic variables are making a bigger difference. On the higher mileage Volt, all tires are at 38 psi. The back left one was at 34 but I filled that a couple days ago. I do notice the alignment is off though. I just find it hard to fathom that one can drive 38 miles and still have an 8 mile reserve while the other has the ICE kick in after 36 miles. That's a 10 mile difference. Perhaps different tires, alignment and age make the difference? Next step is to swap out the tire/wheels and see if that changes anything.

Well, missing the front air dam and lacking LRRR tires, the cars are both set to be less efficient than they could be. Also, tire pressure? I keep mine at 41psi.
 

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Tires the same brand/model on both cars? Tread depth? Tires and psi are known to significantly affect mileage. My winter tires take 5 miles off the battery immediately for example.

Yes, swapping the wheels between the two cars and changing NOTHING ELSE would be very interesting.

Lack of an air dam has more effect on high speed travel efficiency.

After that, I ask about charging habit. Many small top-offs (vs. full discharge/recharge) has been known to limit "battery full" range. Rectified by 3-4 full discharge/full recharge events.

After that, it could be one car has more battery degradation than the other.
 

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Discussion Starter #5
Tires are different and the one with the better mileage has less tread depth. The worse Volt has Bridgestone Turanza Serenity Plus which are hard compound, long lasting tires. The other car has Hankook Roadhandler Sport which are basic all seasons. The drive and charging schedule should be the same except variations in traffic. I commute 37 miles to work, half highway and half heavy traffic. Charge fully at work and charge fully at home. No top offs. Any idea why the estimated kwh used is higher on the car with worse range? Seems counterintuitive.

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Since you only recently purchased the second Volt, this could be another tale similar to the infamous "Tale of Two Volts."

The Gen 1 Volt has a Battery State Estimate Algorithm that tracks the battery state of charge as you drive. When the computer determines the SOC has dropped to the "switch to ICE" point at the bottom of the usable window of battery power, the ICE starts up and the car proceeds on gas-generated electricity instead of on grid power from the battery.

What shows up on the energy usage screen as you drive is a computed "kWh Used" number, the net product of grid power used less regen put back into the battery.

When the car stops for a long enough time, the computer has time to gather additional data and, if needed, make adjustments to the SOC estimate.

Over time, the Algorithm may lose some of its calibration, depending on your driving habits (see below), and if it does, the "switch to ICE" may happen before the SOC has really dropped that far. When that happens, the final kWh Used number can be less than expected.

In the Tale of Two Volts, one Volt has regularly been driven far enough to fully deplete the battery, and is not recharged normally until the battery is empty or nearly so at the end of the day. The car experiences a number of stops during the day (for example, while parked at work, not plugged in) that provide opportunity for the computer to make any needed adjustments to the SOC readings during the day’s trip. IOW, the Battery State Estimate Algorithm gets a full workout, observing the change in SOC from fully charged to fully depleted on a regular basis.

The other Volt gets used a lot less... mostly short trips, quickly back home to get plugged in, rarely uses much of the entire range of the battery’s usable power window. Over time, the Algorithm doesn’t get many chances to gather additional data during a trip to make any needed adjustments to the SOC estimate. Over time, since the car is seldom driven far enough to fully deplete the battery, the computer has few opportunities to maintain calibration by reading data from a full to an empty battery state. The algorithm loses a bit of precision, and the on the fly SOC "estimate" grows a little bit off, and the computer thinks it’s time to "switch to ICE" when there actually is still some usable power remaining.

The Tale of Two Volts seems to indicate this condition can be corrected by running the Volt through a few full charge / full depletion cycles to help recalibrate the Battery State Estimate Algorithm.

Perhaps this is what your two Volts are experiencing... yours often ran through the whole battery charge, while the other in its previous ownership life mostly made short trips and was immediately plugged back in for recharging. You should, of course, also compare the miles/ kWh of the two vehicles. If they are about the same, then perhaps the Volt that gets fewer kWh Used per full charge is suffering from a bit of miscalibration that, it is said, can be corrected by running it through a few full charge / full depletion cycles.

Keep in mind that miles/kWh and kWh Used per full charge are two different issues.
 

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You are in the rare club to A/B test two similar year Volts.

I would absolutely first check the tires. I saw a dramatic difference when swapping tires on my '13. One Volt may also have heavier rubber, which could make a difference. If you really want to do a test--swap the rubber. Also, are the wheels the same?

You should also make sure that you've let the "new" (to you) Volt sit unplugged on empty after a few full charges/discharges. Sometimes that can reset some things, although I've had mixed experience with it.

To be sure, you should check the temp on the rotors to make sure none are sticking. Unfortunately, you've got 136K mysterious miles on the new one and there could be a million things formerly done to it that you are unaware of.

If it's delivering the expected kWh, it would seem unlikely to be a battery issue--at least not yet. At the end of the day, if the battery is performing as expected, but just consuming more kWh per mile than your other Volt, you would have to start swapping out parts between the Volts to start figuring out which piece is the culprit--obviously impractical. I would definitely start with just obvious physical differences. I'm also not sure if a higher-mileage Volt would just consume more kWh/mile because it's just, well, older and all the moving parts are just less efficient than they used to be--especially if parts weren't maintained.
 

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Discussion Starter #8
This is great information, thanks. Based on my estimates, the new to me Volt was driven 35k a year or about 134mi a day with a 5 day work week. I would bet the car was charged at night then driven until empty during day with no charge on the trip home. The battery use was only 40k mi so I wouldn't think there should be much if any degradation but I also know leaving the battery at an empty state is somewhat harmful. The car lifetime mpg was 250+ when I purchased which I knew at the time probably indicated someone had reset it (had a recent transmission service, perhaps reset there). I drove the car back to my place 300 miles and I've only driven the trip to work about 5 times which I know isn't enough to reset any algorithms that are skewed. I knew the range guesstimate would be off but had no idea about the SOC calculation perhaps being off also. I'll swap the wheels/tires and see if there's any difference and also continue driving the same route to see if the range improves.
Since you only recently purchased the second Volt, this could be another tale similar to the infamous "Tale of Two Volts."

The Gen 1 Volt has a Battery State Estimate Algorithm that tracks the battery state of charge as you drive. When the computer determines the SOC has dropped to the "switch to ICE" point at the bottom of the usable window of battery power, the ICE starts up and the car proceeds on gas-generated electricity instead of on grid power from the battery.

What shows up on the energy usage screen as you drive is a computed "kWh Used" number, the net product of grid power used less regen put back into the battery.

When the car stops for a long enough time, the computer has time to gather additional data and, if needed, make adjustments to the SOC estimate.

Over time, the Algorithm may lose some of its calibration, depending on your driving habits (see below), and if it does, the "switch to ICE" may happen before the SOC has really dropped that far. When that happens, the final kWh Used number can be less than expected.

In the Tale of Two Volts, one Volt has regularly been driven far enough to fully deplete the battery, and is not recharged normally until the battery is empty or nearly so at the end of the day. The car experiences a number of stops during the day (for example, while parked at work, not plugged in) that provide opportunity for the computer to make any needed adjustments to the SOC readings during the day’s trip. IOW, the Battery State Estimate Algorithm gets a full workout, observing the change in SOC from fully charged to fully depleted on a regular basis.

The other Volt gets used a lot less... mostly short trips, quickly back home to get plugged in, rarely uses much of the entire range of the battery’s usable power window. Over time, the Algorithm doesn’t get many chances to gather additional data during a trip to make any needed adjustments to the SOC estimate. Over time, since the car is seldom driven far enough to fully deplete the battery, the computer has few opportunities to maintain calibration by reading data from a full to an empty battery state. The algorithm loses a bit of precision, and the on the fly SOC "estimate" grows a little bit off, and the computer thinks it’s time to "switch to ICE" when there actually is still some usable power remaining.

The Tale of Two Volts seems to indicate this condition can be corrected by running the Volt through a few full charge / full depletion cycles to help recalibrate the Battery State Estimate Algorithm.

Perhaps this is what your two Volts are experiencing... yours often ran through the whole battery charge, while the other in its previous ownership life mostly made short trips and was immediately plugged back in for recharging. You should, of course, also compare the miles/ kWh of the two vehicles. If they are about the same, then perhaps the Volt that gets fewer kWh Used per full charge is suffering from a bit of miscalibration that, it is said, can be corrected by running it through a few full charge / full depletion cycles.

Keep in mind that miles/kWh and kWh Used per full charge are two different issues.
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Discussion Starter #9
The wheels seem to be the same. Stock, non chrome OEMs. Good idea on the rotor temps, I have an IR meter I can use to verify. I'm hoping it's a matter of not driving the new one enough to recalibrate the range but I couldn't come up with a reason why one gets 10 miles more real world distance over the other. I'll get the alignment fixed also, perhaps the shop might see something under the chassis that I missed.
You are in the rare club to A/B test two similar year Volts.

I would absolutely first check the tires. I saw a dramatic difference when swapping tires on my '13. One Volt may also have heavier rubber, which could make a difference. If you really want to do a test--swap the rubber. Also, are the wheels the same?

You should also make sure that you've let the "new" (to you) Volt sit unplugged on empty after a few full charges/discharges. Sometimes that can reset some things, although I've had mixed experience with it.

To be sure, you should check the temp on the rotors to make sure none are sticking. Unfortunately, you've got 136K mysterious miles on the new one and there could be a million things formerly done to it that you are unaware of.

If it's delivering the expected kWh, it would seem unlikely to be a battery issue--at least not yet. At the end of the day, if the battery is performing as expected, but just consuming more kWh per mile than your other Volt, you would have to start swapping out parts between the Volts to start figuring out which piece is the culprit--obviously impractical. I would definitely start with just obvious physical differences. I'm also not sure if a higher-mileage Volt would just consume more kWh/mile because it's just, well, older and all the moving parts are just less efficient than they used to be--especially if parts weren't maintained.
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Discussion Starter #11

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I did notice on my car I gained range after a few months of ownership. not going off the guessometer but actual range before the ICE came on.

First, be cruel to it. Drive it like a teenager. Beat on it as much as you can for a week. Aggressive WOT starts and hard braking/ full regen. Get that battery hot and let the cells balance and work under a load. Run it to empty every time, let it rest and then charge it. Set it for departure charging.

After a week of this, re-evaluate. I found batteries can become lazy and this tends to wake up the battery and relearn the SOC in an honest fashion. At least it worked for me, inadvertently as I drive very aggressively in spurts.
 

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Are they both kept in a garage or is one out and on in for example? Are the climate controls the same? Are the night and morning temps comparable between the driving samples? Is there any extra weight in one vs the other etc.

Things like that can add up to differences too.
 

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First, be cruel to it. Drive it like a teenager. Beat on it as much as you can for a week. Aggressive WOT starts and hard braking/ full regen. Get that battery hot and let the cells balance and work under a load. Run it to empty every time, let it rest and then charge it. Set it for departure charging.

After a week of this, re-evaluate. I found batteries can become lazy and this tends to wake up the battery and relearn the SOC in an honest fashion. At least it worked for me, inadvertently as I drive very aggressively in spurts.
This is very interesting. I never tried this with any of my Volts and I've noticed on the last couple drives my Gen 2 seems "lazy" with switching to CS mode at 13.6 instead of the usual 14-14.2. It's annoying as I'm losing just a couple expected EV miles. Will need to try it out. Could be another tool.
 

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Agreed about both not being as efficient but they should be similarly handicapped. I actually swapped the larger dam for the smaller one on the original Volt a month or so ago then removed it all together and didn't see much difference. I think speed and traffic variables are making a bigger difference. On the higher mileage Volt, all tires are at 38 psi. The back left one was at 34 but I filled that a couple days ago. I do notice the alignment is off though. I just find it hard to fathom that one can drive 38 miles and still have an 8 mile reserve while the other has the ICE kick in after 36 miles. That's a 10 mile difference. Perhaps different tires, alignment and age make the difference? Next step is to swap out the tire/wheels and see if that changes anything.
The alignment being incorrect can murder your mileage on any car. Probably your problem. I would say a trip to the best alignment shop you can find would be a good idea before you go to the trouble of swapping parts.
 

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Discussion Starter #16 (Edited)
They are both kept outside in the same environment. If anything, the one that gets better mileage has a disadvantage because I have a spare tire in the trunk. Both climate controls are set the same. The only difference is that the one with better mileage has car pool stickers so there's slightly less stop and go traffic when I use the HOV lanes. That's actually another disadvantage for the good one.
Are they both kept in a garage or is one out and on in for example? Are the climate controls the same? Are the night and morning temps comparable between the driving samples? Is there any extra weight in one vs the other etc.

Things like that can add up to differences too.
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Discussion Starter #17 (Edited)
Thanks, the steering wheel is about 2 degrees off so it's definitely bad. I'll get it fixed and see if that makes a difference also.
The alignment being incorrect can murder your mileage on any car. Probably your problem. I would say a trip to the best alignment shop you can find would be a good idea before you go to the trouble of swapping parts.
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Discussion Starter #18 (Edited)
That's hard to do when I've been anxiously watching the range meter but it's an easy thing to try. On my other one, I've definitely gained range recently but I attributed that to mainly warmer temps. I've been driving the bad one to empty then charging it in departure mode. Both get charged overnight on 110 since im on use based metering.
I did notice on my car I gained range after a few months of ownership. not going off the guessometer but actual range before the ICE came on.

First, be cruel to it. Drive it like a teenager. Beat on it as much as you can for a week. Aggressive WOT starts and hard braking/ full regen. Get that battery hot and let the cells balance and work under a load. Run it to empty every time, let it rest and then charge it. Set it for departure charging.

After a week of this, re-evaluate. I found batteries can become lazy and this tends to wake up the battery and relearn the SOC in an honest fashion. At least it worked for me, inadvertently as I drive very aggressively in spurts.
Sent from my Pixel using Tapatalk
 

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This is very interesting. I never tried this with any of my Volts and I've noticed on the last couple drives my Gen 2 seems "lazy" with switching to CS mode at 13.6 instead of the usual 14-14.2. It's annoying as I'm losing just a couple expected EV miles. Will need to try it out. Could be another tool.
I had read somewhere that a battery never exposed to a full load ends up with altered chemistry and the battery equivalent of tin whiskers. Getting the battery to it's full current capability once in a while forces a restructuring/reshuffle and "cleans the carbon out", so to speak.

Here's a good read on formation cycling. Apparently a battery's "personality" is decided by it's initial charges.

https://www.sciencedirect.com/science/article/pii/S0378775317300113
 
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