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Discussion Starter · #1 ·
Anybody know what the criteria is for Chevy to declare the HV battery bad? Just like to know where the line is, so I can continue to complain about my range loss or just live with it until I can get rid of it.
 

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The car monitors the battery internal resistance and will set a code and illuminate the check engine light if the battery degrades to the point replacement under warranty is appropriate. As far as I know, that hasn't happened to anyone.

Range loss is very hard to accurately measure on a GM EV, because they don't give you any absolute measures. The range on the screen is an estimate based on recent consumption and temperature as well as battery state of charge, and will naturally fluctuate throughout the year just from temperature variations.
 

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The Gen 1 Volt’s 8 yr/100,000 mile battery warranty says this: "Depending on use, the battery may degrade as little as 10% to as much as 30% of capacity over the warranty period." This has been increased to 10% to 40% for the Gen 2 Volt and Bolt.

Math seems to say that if a Gen 2 Volt has, over time, "lost 40% its oomph" (rather than had a repairable or irreparable problem), the quantity of usable power in a full charge could shrink to ~8.5 kWh usable and might still be considered to be within warranty standards.

For a 2013/14 Gen 1 Volt, that usable window could shrink by 30% to ~7.5 kWh and might still be considered to be within warranty specs if the problem is degradation, not a more serious problem.

A loss of 1 kWh or so could well be the result of simple degradation that falls within warranty standards, but one would think this happens gradually over time, not so rapidly that it is noticeable. (I note the driver of the 2014 Volt that had the range loss following the "buzzsaw bearing repair" was still getting 10.2 kWh on a full charge according to his mygreenvolt app, so his battery replacement must have been done for a reason other than simple degradation. His final entry in that thread suggested his Volt was still getting fewer miles/kWh than he was getting prior to having the bearing problem, i.e., the new battery didn't solve the range loss problem.)

It is possible to have a service department evaluate the battery. The warranty manual says: "A dealer service technician will determine if the battery energy capacity (kWh storage) is within the proper limit, given the age and mileage of the vehicle. Typical tests can take up to 24 hours." I would think any such diagnostic test would require a fee, and it would not be reimbursed if the end analysis was that the problem is ordinary degradation that falls within warranty limits.

IOW, might your range loss arise from some other source, such as a sticking brake caliper, new tires, change in tire pressure, wheels out of alignment, etc.?
 

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After almost 30,000 miles, I still get 14.0 kWH used when I use up the battery entirely. Does than mean it has seen 0% degradation... or they are adjusting the charge window behind the scenes to hide some potential loss?

Mike
 

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Anybody know what the criteria is for Chevy to declare the HV battery bad? Just like to know where the line is, so I can continue to complain about my range loss or just live with it until I can get rid of it.
What kind of range loss are you experiencing? Are we talking about a Gen1 or Gen2 Volt here? Have you owned your Volt through a winter season before? A large range loss is normal in cold weather...
 

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Discussion Starter · #7 · (Edited)
What kind of range loss are you experiencing? Are we talking about a Gen1 or Gen2 Volt here? Have you owned your Volt through a winter season before? A large range loss is normal in cold weather...
It's a 2013 Gen1 Volt that I've owned for 3 years. Was working perfectly until 6 months ago. The stator bearing (buzz saw sound) went out. After that repair I start noticing a reduction in electric range on the same daily commute to work, and the kWh used on the display dropped to 9.6. For over 2 years the kWh used has always given me 10.8kWh without fail. I use to get 38-42 miles or more before switching to gas. Now I can barely get 30-32 on a good day (warm day). I bought an OBD2 device and use Torque Pro to monitor the battery. The cell voltage varies as much as 0.2 volts charged to 1 volt discharged. The battery management computer reports a capacity of 13.1kWh. The only conclusions I can draw. I have some bad cells that drop in voltage while discharging lowering the average voltage enough to trigger the generator to come on. Thinking the battery is low.

Using Mygreenvolt app to monitor efficiency. I've notice my efficiency as also been dropping slowly, and is down to around 3kWh/mile. Was wondering if 12 Volt battery is bad, drawing extra power to keep it charged while driving. Going to have it tested by someone else next. The dealer said it was good. I don't trust them, since there is something going bad and they can't explain the range loss.
 

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I'd think it's more likely that sagging voltage during high power draw events with a nearly depleted battery would start showing themselves more than just capacity degradation(since the top and bottom buffers can hide some of that). But maybe I'm wrong.

I do recall some people getting a "propulsion power reduced" message with higher power draws and <30% SOC on gen 1 Volts and getting new battery sections, or those getting a new battery section when a cell shorts out, but I haven't really heard of someone getting an outright "battery capacity degradation" warranty replacement.
 
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