issue with battery or battery management system, missing 20%

I have found same problem on forum also with year 2013 and around 56K miles (90.000km), strange.

My update: TAC told us to check voltage of every cell.

More from forum:
gm-volt.com/forum/showthread.php?316794-Bad-Battery-Cells-symptoms-2-3-bar-loss-2013-56K-miles

Hi,

New (to me) Volt owner and poster here...

I recently bought a 2013 Volt with ~56K miles that seems to be in great shape except for one problem -- the battery capacity! Here are the symptoms:

The battery shows that it is completely charged (10 bars) upon startup.
After basically pulling out of the driveway, the battery capacity drops 2 or 3 bars. No pre-conditioning has been done and I promise that I'm not doing donuts in my driveway.
The same symptoms show up whether charging at home on 120 V (either 8 or 12 amps) in a 50 degree F garage or at a level 2 Chargepoint station.
After drive about a mile, the energy usage screen shows that I've already used up 3-4 Kwh (with no climate control on and driving gently)
The total range (guess-o-meter) shows 30 miles of range upon startup but drops to upper teens after about a mile.
This all happens even when driving extremely gently (100% climate control efficiency and 85%+ driving efficiency).



It certainly seems like there must be some bad cells or modules in my pack. Since I've only had the car for a week, I'm trying to "recalibrate" the battery by completely charging/discharging (by purposefully not charging at work and driving to battery exhaustion on my commute home) as has been suggested before, but there doesn't seem to be any improvement yet.

It seems that these symptoms are very similar to those described in the thread on this forum titled "10-mile-range-loss-when-driving-only-2-miles" (sorry, I can't post links yet due to being new). The author of that thread ended up getting a battery replacement, so I fear that it where I'm headed.

So, wise Volt veterans, what should my course of action be? Schedule an appointment at a local dealership? Are there any dealerships in the Denver area that are known to have good Volt technicians? How much trouble is it to get a dealership to repair something under the Voltec warranty? Any other advice?

Thanks in advance for your collective wisdom.

OP's Update:
I got the Volt back about 2 weeks after getting it towed to the dealership. Here is a summary of the invoice:

- Trouble code P0AFA and vehicle will not enter propulsion mode
- Scanned and found cell variation of 0.58 V (pack voltage of 338 V and capacity hex value of 01C8 = 16.3 kwh [01C8 = 45.6 Ah; 45.6 Ah * 358 V / 1000 = 16.3 kwh])
- Lowest 2 cells were 65 and 66
- Data sent to TAC which advised to replace battery section #2

I've been driving for a couple of days with the new battery section and all seems well. AER has been in the upper 30s in cool weather. The energy used for charging at the kill-a-watt meter has shown 13.2 kwh. With 80% efficiency, that's 10.5 kwh into the battery. All in all, the numbers look good and it looks like I finally have full use of the battery!

I'm satisfied with the Voltec warranty and Medved Chevrolet in Wheat Ridge, CO for performing the repair. Thanks to all for posting and helping to get my Volt up to spec!

More than 2 kWh are used for first few kilometers UNRESOLVED

1. CHARGING

Charging process is normal until 72,2% SOC-R (81,9% SOC-U), then stop and stay there for half an hour, after that percentage jump to 83,9% SOC-R (SOC-U 100%) in second, this happens 1,5 before estimated finish.

Symptoms

a) Percentage stopped at 72,2% SOC-R for about 0,5 hour.
b) Percentage jump to 83,9% SOC- R fully charged, normally would be more than 87%.
c) Percentage jump to 100% fully charged happens 1,5 hour before estimated charge finish, normally takes 15 minutes to 30 minutes more than estimated charge finish.

Recorded moment when percentage jump to fully charge in seconds.
youtube.com/watch?v=_0qJPRzMAkg&feature=youtu.be

2. DRIVING

For the first few kilometers consumption (kWh) is not normal. I have donwhill road for 2 km and use 2 kWh, normally I use 0.2 kWh to that point.

Symptoms

a) SOC-U 100%: 2 kWh are used in first 2 kilometers (downhill), normally 0.2 kWh is used (no A/C)
b) SOC-U 70%: 0.2 kWh is used for first 2 kilometers (downhill), consuption is normal.
c) After first 3 kWh is used consumption become stable .
d) Total range is now around 50 km, normally 72 km (summer).

View attachment 154363
View attachment 154365

3. SERVICE
a) all 96 cell have normal voltage when fully charged 3.9V,
b) Hybrid Powertrain Control Module B was updated (probably not configurated, poor staff knowladge)
c) Car don’t show any errors

Conclusion

It seems like computer compensate 2 kWh for charging jump from 81,9% SOC-U to 100% SOC-U. This happens 1,5 hour before estimated charge finish. Range dropped for about 20km to 50km, if we add 19% from charging jump we get 70 km of total range.

If anyone had same experience please write.

Well, problem solved long time ago .

If cells voltage is inbalanced for example: highest cell 4.020 and lowest cell (also average) 3.900, this mean that car will stop with charging -> when 1 cell reach full charge.

And now on computer you will get 100% fully charge, in reality only 1 cell is full and others are on average 3.900.

Computer will solve this problem with new calculation after few minutes and give you only 80% charge.

The problem here is huge inbalance between cells (0.100+V) and battery needs time to deal with this.

I solve this issue only this way:

To correct inbalanced battery I charged battery to 60% and drive around only on hold for about 14 days. If battery drops bellow 50% I charged it back to only 60%.

After 14 days you will have balanced battery with 0.015 delta between highest and lowest cell.