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Discussion Starter #1
I have two IDENTICAL Volts, with one exception. The good one was delivered directly from the factory to the dealer to me. The other sat on a lot, unloved, in Texas for several months before it was acquired to sell to me by Stingray Chevrolet. Both are 2012s, blah blah, when I mean identical- the only difference is the EXTERIOR paint. However, I now fear that the unloved Texas Volt had its battery cooked over the summer of 2011.

The good Volt gets me 40-50 miles per charge, reliably. It is the one used most often. The bad one cannot seem to break 40 miles. I have driven them on identical trips. Where the good one will get 44 miles, the same trip will yield 37 miles on the other. KWH used is routinely above 10 for the good one and routinely below 10 for the other (before depletion). [The problem has only recently become obvious because of the difference in drivers and locations over this past summer.]

Since I know that I am the same driver (and this is FL, without the temperature effects found up north), I KNOW that one battery is underperforming. I will be taking this to the dealer for a diagnostic on the battery (100 miles away). I am curious as to others who might have had underperforming batteries and how it was dealt with by the dealer. I also don’t want to be sold a bill of goods as to what the specs say. From reading this forum, it seems clear that 9.5-9.8 kwh out of the battery should not be the acceptable amount before depletion. I certainly hope that I do not have a fight on my hands, but it would be nice to have some ammo in the magazine before the service department starts to tell me what they think should be done. While I have read that the kwh display is something that depends on some algorithm, my mileage between the two Volts cannot be second guessed and is the only real thing that matters in terms of my Volt performance.

Comments? (Especially from anyone who had a defective battery replaced)
 

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The good thing is that the battery is under warranty and, unlike the warranty you get from Nissan or Tesla, your Volt warranty actually covers capacity. Good idea to get it tested. I'd also call your Volt advisor and talk to them about it. Might be an interesting case from an engineering standpoint. It's possible of course that the batteries will vary slightly -- cells won't be the same and you hope they put all the lower performing ones together -- but not by the amounts you're talking about.
 

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Can you tell from the VIN if the one with the "good" battery was one of the later 2012 models built?

I don't know exactly what the cutoff is, but I know that people with "late" 2012 models have reported getting more usable kwh's per charge than earlier builds, and it's suspected that the "late" 2012's got the same improved battery cells as the 2013's, which added 0.5 kwh's to the battery capacity. This might not explain the extent of the difference between your 2 Volts, but it might explain part of it.

Also, for reference, with my 2013 (that I bought straight from the factory), I typically get 10.3-10.5 kwh/charge. On a 2012 with the "old" battery, that would equate to 9.8-10.0 kwh/charge. So it's a bit better than your 9.5-9.8, but only by 2-3%, which isn't a ton. Still, I'd be interested to hear what you find out.
 

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Can you tell from the VIN if the one with the "good" battery was one of the later 2012 models built?

I don't know exactly what the cutoff is, but I know that people with "late" 2012 models have reported getting more usable kwh's per charge than earlier builds, and it's suspected that the "late" 2012's got the same improved battery cells as the 2013's, which added 0.5 kwh's to the battery capacity. This might not explain the extent of the difference between your 2 Volts, but it might explain part of it.

Also, for reference, with my 2013 (that I bought straight from the factory), I typically get 10.3-10.5 kwh/charge. On a 2012 with the "old" battery, that would equate to 9.8-10.0 kwh/charge. So it's a bit better than your 9.5-9.8, but only by 2-3%, which isn't a ton. Still, I'd be interested to hear what you find out.
My good Volt rolled off the line in October/November of 2011, and as far as I know, this is well before any tweaking may have occurred that we heard about- and I never see the kwh on this Volt that I see 2013 owners discuss. 10.3 kwh is pretty much my UPPER number and as you point out, 10.5 kwh is not uncommon for 2013 owners. But, the difference in kwh cannot be equated percentage wise to the MILES of difference (37/44= a 15% difference in what really counts).
 

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*** has made it clear that the KwH should not be used for comparisons. Presumably that is not the measure the dealer will use. My 2012 sometimes shows 9.7 in the winter (now) and goes over 10 in the summer.

Speculating, there is a parameter called HV battery estimated capacity that the dealer can read. Based on some patent reading which may, or may not apply, there is possibly another value stored in memory which was the manufactured state. I'd look for GM to use this, or some other objective measure to determine percent degradation. 10 to 30 percent over the life of the warranty is cited in the warranty's preamble. The shape of that curve should be linear.

The range difference between the cars is 19%.

Before going much further I'd check alignment, tire condition(s), brakes, etc. Stuff you would not catch in the driveway which could easily explain range difference. My car is very sensitive to tire inflation.

Folks on the forum that have had low voltage cells typically threw codes and GM was very fair in handling the issues. The decision will not be made at the dealer level alone. ...GM will be involved.
 

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My good Volt rolled off the line in October/November of 2011, and as far as I know, this is well before any tweaking may have occurred that we heard about- and I never see the kwh on this Volt that I see 2013 owners discuss. 10.3 kwh is pretty much my UPPER number and as you point out, 10.5 kwh is not uncommon for 2013 owners. But, the difference in kwh cannot be equated percentage wise to the MILES of difference (37/44= a 15% difference in what really counts).
When was the first 2012 built?

Can I read out KWH used on a 2011 Volt?

Thanks
 

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It is possible that the poor performing Volt battery used up its entire charge while doing thermal management. GM reserves the lower and upper portion of the charge to give it longevity.
In my experience a completely dead battery damages the cells. They can grow dendrites causing shorts. Result lower range.
Below is an interesting link about the battery.

http://www.driveforinnovation.com/teardown/volt-battery-teardown/
 

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Discussion Starter #8
Re: alignment, pressure, etc.

Not an issue, as CS mode is the same mileage for both Volts (about 40 mpg on the comparison trips). Sorry, I should have mentioned this detail.
 

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My 2011 gets crappy range, but it does seem to take a normal recharge (reported by the Coulomb charger). I believe if I tried pursuing this it would only take me down a useless rat hole.

In somewhat related news, stopped at the Delaware rest area on I95 yesterday and saw the Tesla superchargers. Looking more and more like Tesla is the way to go forward.
 

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Interesting. I presume when you say one gets 44 and the other only gets 37 you are talking about the actual miles (not the estimates) on the same trip with similar temps on those trips.

The first direct comparison I've seen suggesting any range issue on Volt batteries. Since you have remove most of the variables (driver, terrain, temp), the 19% difference is not easily explained. (If its estimated range its possible that one sensor is off and impacting it).

As someone that bought a unloved TX volt in Aug '11, I worried about this a bit. Mine is, however, providing excellent range, but maybe it was better cared for -- at least left sitting with virtually no charge.

It is possible the weaker pack will be declared normal, and that the "good" pack is just above spec. Batteries have some natural variability and so GM may have been conservative and used the bottom quartile as their "benchmark" and for epa testing. It is also possible its more of a sensing issue than actual battery, but it only takes a few bad cells to bring down the whole pack. But it could be what you fear. Let us know what happens.
 

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Could be wrong about this, but I believe GM only stated 35 mile range, and the warranty doesn't kick in till well under that. So, you're probably stuck. My own Volt has gone from showing 10.5kwh/charge (available before CS kicks in) to 9.5, and no matter what WOT says, that's a significant reduction for a car with only 7k miles on it, that did get the 10.5 last winter when it was colder than it was when I measured the lower number this year. And range tracks just fine with that number - when it says 10.5, I get 10% more range than when it says 9.5. In other words, that estimate is pretty darned accurate. Wish I had one that good for my trading job.
 

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Re: alignment, pressure, etc.

Not an issue, as CS mode is the same mileage for both Volts (about 40 mpg on the comparison trips). Sorry, I should have mentioned this detail.

Good call, if the drivetrain efficiency to the road is the same, that narrows it down. Given the near normal kWh reading is based on delta SOC which is independent of capacity, the range comparison is persuasive. it is probably the battery or it's management systems. As an afterthought call OnStar and check for codes. Good luck.
 

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I'm going to bet GM has a fixed threshold on a battery reading where they will entertain replacing the battery. It might not even be a call your dealer gets to make- I'm betting they get the battery geeks involved at Volt HQ. Then too, the replacement may well be a refurb battery pack, not a brand new battery. The ease of this process may depend on your local dealer. Who knows how excited he may be about a warranty problem with something bought elsewhere.

I'd imagine too that the engineers will show some interest in a potentially declining battery, cause you can test things all you want at the lab and the track, but the real test is in the real world.

But too, you may also have examples of a good range car vs a bad range car.

And, as they say, your rights may vary from state to state..........
 

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My battery was replaced about 3 months ago, the new battery shows 9 to 9.9 KWH before switching to gas. The old battery showed 9.8 to 10.6 KWH before switching. Also appears to be about 2,to 3 miles of range less maybe. Did I get a defective or weak battery? Or is the KWH inaccurate? Does the KWH come from the car or battery computer? It would appear that voltage is what triggers the gas start, if you drive aggressively when the battery is near switch point it will switch sooner.

I posted this here about a month ago. My car a 2012 built October 2011 did better with the original battery, best for original battery was 43 miles best distance for new battery has been 37 miles. Christmas day set a new low in electric mileage at 17 miles KWH read 10.1 highest ever for this battery, average temp that day -5. Yesterday our mileage was up to the impressive range of 19 miles, KWH 9.5 average for this battery, temp this day +5.
I may also write a little about having to change driving habits on ice with the volt.
 

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It would be nice to not have to worry about rights or have to battle with General Motors and/or their dealerships.
Not sure what you're suggesting, but so far GM has NOT behaved like Nissan or Tesla. No pointing to the four point type on page 17 of the disclaimer you signed when you picked up the vehicle. If anything GM has gone beyond what you might expect.
 

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Discussion Starter #18
Update, contacted by GM Customer Service asking for VINs- and I didn't even contact them myself. Daughter dropping off vehicle at Stingray at 9AM. I hope this is as much a learning experience for them as for me- and that all of GM dealers (perhaps) get tutelage on not ignoring their Volts for extended periods.
 

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The suspense mounts.....is this the first heat degraded Volt battery or....? :)
 

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The suspense mounts.....is this the first heat degraded Volt battery or....? :)
Very doubtful, despite the "speculation".(the current owner really has no idea how it was stored/charged/treated in TX, but there is a service history to go from)
More likely just some other issue or defect since there's no actual documentation of "degradation" taking place.
WOT
 
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