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Discussion Starter #1
So this started happening 6 months to a year ago and got steadily worse. What happens is the car switches from battery to engine with about 10 miles range left on battery. It then toggles back and forth between battery mode and charge sustain every few miles until battery actually depleted. Happens mostly at highway speeds during my 32 mile work commute. It also seems to switch over sooner when the battery drain is higher (the faster I'm going the earlier it flips to charge sustain mode) Started probably a year ago, but the battery level at which it first switches over has progressively gotten higher.

The paragraph above is exactly what I gave the dealership (Gateway Chevrolet in AZ) when I took it in. The tech notes were that they looked for any software issues, test drove the car and confirmed engine switch over happened and that 'no mechanical issues found'. They gave it back to me with no changes made for that issue (I also had them fix the steering sticking issue, TSB – PI-1322, SC-14232).

Just the note of 'no mechanical issues found' is enough to know they didn't understand the problem and didn't call me to ask any more questions. They told me it was ready and I could come pick it up. I've taken it to them in the past and sometimes they're slow but they've always eventually resolved the issue. I hate dealerships.

Anyone out there have a GOOD dealership for Volt service in the phoenix area? Or know of a specific TSB I can point them to for this? I've looked and haven't found anything exactly like this.
 

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It sounds like the propulsion battery is failing. Can you run it all the way down and see how many kWh's you are getting out of it? It might be worth it to have the dealership perform a full battery test.
 

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Discussion Starter #3
I just found this other thread, which seems similar to my issue.

https://gm-volt.com/forum/showthread.php?327395-Switches-to-gas-mode-with-Battery-Charge-remaining

I have not tried stopping and restarting the car mid-drive, but in my case it toggles between the two modes frequently and making a stop and coming back and driving again hours later gives the same behavior. There are no DTCs, no indication the car thinks anything is wrong.

In answer to your question, I run it empty every day, as I drive 75 miles a day to/from work. The kWh's used varies due to the issue and the car being confused about the charge remaining. new it would use 10.4 kWh, 7 years on it was around 9.0 kWh, but now its all over the place, because the early regen adds charge to the battery that wasn't there originally and gets counted on the usage display when it finally bottoms out and stays in CS mode.
 

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I have the same issues one my 2012 with 155k on it. No codes but voltage drops when I monitor the battery on the Torque app. Have started looking for replacement HV battery or will decide to maybe just trade it in as is.
 

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Discussion Starter #5
And I would be too except I still have a smidge of Voltec warranty left, I'm at 98,100 right now and my 8 years wouldn't tick over until this December. I intentionally took it in before the warranty was up so I could have the problem on record. At least I have the paperwork from this visit describing the issue with the mileage recorded.
 

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It might be worth it to have the dealership perform a full battery test.
+1
It sounds like your getting voltage fluctuations from a failing cell/segment. I'd bring it back and have the HV battery tested. You'll want this identified or ruled out while the warranty is in force.
 

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Discussion Starter #7
That seems to be the consensus so far. and that's probably the plan. I have about 6 weeks left before my work commute will kick me out of warranty. I HATE taking my car to the dealership for service, first because I need the thing, and second because like a lot of people, my experiences with them typically are less than pleasant. If I had to guess I'd say I've had more times where they couldn't or didn't fix the problem right the first time than when they did.
 

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I've had my Volt to two dealerships in the Phoenix area, Autonation in Mesa is awful. I have been using Earnhart in Chandler, used to be Thorobred. Service advisor I use is Rick Hamilton. Maybe give him a call???
 

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RedBowtie03,

I think that are in a good position to get a new battery or module under warranty in my opinion. I would always argue for a complete new battery. Anyways, I would take the car back to the dealership and tell them to look at all 96 battery cell groups at the time when the car is just finishing charging. They should all be around 4.07v, plus or minus .01 volt. They should make note of any cell group voltages above all of the other cell groups. Have them print out the voltages for every battery group at this state of charge. They should leave the computer hooked up and go drive or have a porter go drive the car very gently until all of the battery range remaining has been depleted. This means it shows zero range remaining on battery, not just when it kicks over to gas the first time. At that point look at the 96 cell groups again and see which one(s) are significantly below the average cell voltage. It should finish at around 3.55-3.6v per cell group. If there is a bad cell group or groups then there will be a low voltage cell group or groups and this will be enough to get TAC involved. Ask for a print out of Cell Group voltages at the top and bottom of charge. Do not accept no for an answer.

I would do this before either getting my VCX Nano setup or buying your own. They have to verify anything you find anyways so it will be likely cheaper and more time efficient to ask them to do the test first. Now, they may give you the runaround and say they did the test and they cannot give you a printout since their printer is broken, yada, yada, yada. If that happens you will have to get your own proof or find another dealer, assuming the test came back that cell group voltages were OK.
 

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Discussion Starter #10
Thanks for the detailed reply Jiminy, I appreciate it. I plan to request they run the test as you outlined above and see what happens. I agree that if I can get them to find the issue themselves it will save some time and some headache.
 

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I look forward to hearing your results!

With the help of a coworker I shot a video today showing the diagnosis procedure using VCX Nano and the GDS 2 software:

 

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Great video. Going to get me one of those soon......but you really need to clean up your office. :p;)
 

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Discussion Starter #13
Great video, thank you. Question, does the GDS2 software come with the Nano or is it a separate purchase/download?
 

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VCX Nano and the VMWare version of GDS 2 come as a package.
 

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Will this be able to tell you what section of the 3 packs of cells is in? Dealer says that they can do specific sections instead of a whole battery.
 

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Discussion Starter #16
Update

So, I changed my mind and bought the Nano. Got it this morning (Amazon Prime ftw), set it up on my laptop and took some measurements.

I captured the cell voltages at full charge, took a drive and filmed the dash with my GoPro, and captured the cell voltages after spending some time in CS mode. I also grabbed battery temps after the drive, and the control module data screen. I've attached the data files here. No video posted because its 13Gb and editing takes forever. I'll try to chop it up and maybe get a clip up here later of the first switch-over.

The fully charged voltages are all between 4.08 and 4.09 volts, except cell 77 at 4.07v, and cells 2, 8, 15, 17, 76 at 4.10v. None of which seems like anything to write home about.

The depleted voltages are spread a little more, ranging from 3.43 to 3.52 volts, except cell 96, at 3.40v. I don't know if this tells me anything. I do have the video evidence of the issue, so I can at least show the dealership exactly what I'm talking about.

FYI, the dates shown in the docs are goofy because I forgot to set the clock in the virtual machine beforehand.
 

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Looking at your numbers is pretty interesting. It is not doing exactly what my battery pack did when it glitched. What I might suggest as the next step is to have someone else drive the car while you sit in the passenger seat with the laptop. Try to do it on a day when you are pretty sure the conditions are right for a glitch. Try to use the heater. Have them put the car under load while you watch the following cell groups:

1 and 2
5, 6, 7
76 and 77
95 and 96

It might take more than one test drive to get enough data. I would look for significantly sagging voltages in one of these groups when you place the car under a heavy load. You might even experiment with GDS 2's graphing feature which might allow you to do this without a helper since all sessions are recorded by the program.

One of my theories is that cell groups at the ends of the 96 cell group string are placed under more load than the middle groups. I need to do some more research on that.
 

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I scanned a 64k mile 2014 Volt yesterday at the bottom of charge and the cell group voltages were all within a hundredth of a volt of each other. Has anyone else seen this and if so, was the car a high mileage (>100k) or low mileage (<100k) car? I was very surprised.

2014volt.jpg
 

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Discussion Starter #19
Thanks for looking at my battery voltage data Jiminy. I noticed that groups 1 and 96 in particular seemed to be outside the other groups normal values.

So here's an update on where I'm at with my Volt. Unfortunately I'm up against the warranty wall as far as testing the battery by myself. I had to do a lot of extra driving this week and as she sits in the garage tonight I'm at 99,950 miles. I just made an appointment with the dealership for Tuesday to have the battery load tested, agreeing to 2-3 hours of diagnostics fees ($140/hr), and the service advisor agreeing a repair/replace would be covered under warranty if battery issues are found. They have also agreed to get TAC involved with this.

I posted up a cropped-for-time version of last weekend's drive video on youtube, and sent the advisor the link, to show them the behavior I was describing and prove that there is in fact a problem. It's here, https://www.youtube.com/watch?v=HB9Fh1fhvuw if you want to take a look.

The advisor's response to the video was less than thrilling, trying to sell me on the story that this is all part of the normal aging and loss of capacity over time of the battery, and that GM would not replace a battery just because it had lost range, but they would take another look if I agreed to the shop time costs. Honestly, either he doesn't understand the tech that well or he doesn't want to, for whatever reason. I'm going to leave it sit uncharged all weekend and take cell readings before I charge it just a bit to deliver it to them. Unfortunately they can't take it until Tuesday, because the Volt tech (whom I have little faith in given his first attempt), is off on Monday.

So wish me luck. I really want to hang onto this car for quite a while yet but I'd rather not have to do the Jiminy Procedure (tm), and replace it myself. BTW, if I do have to go that route, I'm going to need those full connector order-of-operation instructions. :)
 

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I watched the video and it certainly behaves just as my 2011 Volt did prior to replacing the pack. Running for 2 miles and switching back to EV operation is a dead ringer. I'd prepare to make some serious noise with your dealer to get TAC to take your issue seriously. You might even engage a lawyer to write a persuasive letter to the dealership and Chevrolet to get this fixed. The car's market value is pretty much nil with this issue. This is not normal ageing of the battery. This is a failure of one or more cell groups.

Chevrolet issued a TSB/reflash for this exact thing on 2017 Bolt EV's. They put in an early warning feature in case a cell group was going bad. I cannot see why they don't do it for the Volt. The difference is that if a group goes bad in a Bolt EV they have to replace a 60 kWh pack and you are dead in the water. The Volt has an ICE backup so you shouldn't have to walk BUT there are occurrences where there is a big fault rendering the ICE not available and if both of those things happened at the same time you'd be in trouble. Or at least in the same exact predicament that the '17 Bolt EV reflash is hoping to preclude.
 
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