Clanch
Posts: 9
Joined: Thu Feb 20, 2020 1:08 pm

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 8:36 am

My understanding is the batteries are assembled in Braunschweig Germany.
What I do find fascinating, is 1 low voltage battery nodule in the battery pack can shut down the whole car. I would think the battery management computer could isolate that low voltage nodule and give the customer a warning. But not shut down the car!!!

Dealing with the five German automakers for so many decades, I find Volkswagen Audi the best of dealing with problems for the customer.

As I said before I really like the car and so does my wife. But shutting a car off while driving just because one nodule has low voltage is extremely concerning to me.

f1geek
Posts: 851
Joined: Fri Jan 23, 2015 1:18 pm
Location: SF Bay Area

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 9:18 am

Yes, VW assembles the pack, but Samsung SDI makes the individual prismatic cells. The 35.8 kWh e-Golf battery pack is created in a 88s3p (s=series, p= parallel) configuration, and contains a total of, you guessed it, 88x3=264 cells. At a nominal cell voltage of 3.67 V, the pack voltage is 88 cells *3.67V per cell=323 Volts at the pack level. All of the electronics in the car for charging, powering the motor, HVAC, etc. is built around the cell voltage varying from about ~3 volts at the low end (~264 Volts at pack level) to about ~4.1 volts at the high end (~361 Volts). If one cell in the group of 88 cells wired in SERIES becomes disconnected or has a major issue such as an internal short, BMS will attempt to prevent a fire and shut the whole system down. If a cell became disconnected, the voltage would drop to 0 for that single group of 88 cells in series. It is not as simple as the BMS deciding to "isolate" a cell - the system can not work in that fashion as it is designed. There is no way to isolate a single cell because they are all interconnected in series within each group of 88 cells. Since it looks like the "battery cell defective" code means one cell is dead, the car must be shut down or your wife's car may have become very toasty.

I wish you the best of luck in getting this figured out. VW will probably need to remove the battery pack and replace the faulty cell or repair the connection (depending on the true problem). How are you able to reject the car and get all your money back if this is not a lemon law issue?
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior

Clanch
Posts: 9
Joined: Thu Feb 20, 2020 1:08 pm

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 11:13 am

Thank you for the information. Most manufacturers would rather take a car back, then dealing with lemon law and having the vehicle Vin tag with lemon law buyback. And the manufacturer has to pay all attorney fees for the lemon law case.

I had looked at the wiring diagram on aldata and saw the batteries were wired in series. Like an old Christmas tree light strand.

Let's see what Volkswagen does.

Clanch
Posts: 9
Joined: Thu Feb 20, 2020 1:08 pm

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 12:33 pm

Also German manufacturers over the decades have written the software parameters way too tight. The fault code is for low-voltage not open circuit, so that battery module should have a good connection and ground. I will ask how far that module is out of spec. This way we'll find out how tight the parameters are, to shut down the car while driving.
The other fault codes I'm guessing our a cascading events from the low battery module voltage out of balance.
This failure does interest me, in a engineering way.
As manufacturers go, Audi Volkswagen tend to have the friendliest and easiest software to deal with. Next comes BMW and Mini. Mercedes-Benz is a complete pain in the ass. Porsche software tends to be like from the 1990s.

f1geek
Posts: 851
Joined: Fri Jan 23, 2015 1:18 pm
Location: SF Bay Area

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 6:26 pm

If you think 88 cells in series is a lot, think about the Porsche Taycan. It has a ~800 volt pack architecture. Porsche says there are 396 cells at 64.6 Ah each. At 3.67 volts nominal (assuming similar battery chemistry as e-Golf) that means two parallel sets of 198 cells in series. That give a nominal voltage of 727 Volts for the pack. I wonder what the tolerance is for those 198 cells in series? Maybe because it is liquid cooled, there is a bigger tolerance? In any case, I think you are right that the cell in your e-Golf did not completely fail, but is out of tolerance. Luckily, I suspect most e-Golf drivers have not encountered this issue. When I have looked at my car's individual cell voltages, I have not recorded the live readings, so next time I take a peek, I'll record some values to see how close some of the cells really are.
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior

eGolfJoe
Posts: 88
Joined: Thu Jul 04, 2019 10:57 pm

Re: Electrical system failure: Stop!

Sat Feb 22, 2020 11:24 pm

f1geek wrote:
Sat Feb 22, 2020 6:26 pm
I have not recorded the live readings, so next time I take a peek, I'll record some values to see how close some of the cells really are.
FWIW, I've only looked at mine at rest after a 50 mile freeway drive with 20% charge remaining and all cells were < 0.1V of each other. This was at ~5000 miles. After 100% charge, they were even closer together, which you'd expect.

f1geek
Posts: 851
Joined: Fri Jan 23, 2015 1:18 pm
Location: SF Bay Area

Re: Electrical system failure: Stop!

Sun Feb 23, 2020 5:48 pm

Ok. Had a look at my car's battery pack today. There are a total of 88 cells available for voltage monitoring. I found the maximum voltage was 3.654 V and the minimum was 3.645 volts. That is a delta of 0.009 V. These cells are REALLY close together in terms of voltage. Also, Cell1: 3.652 V, Cell2: 3.652 V, Cell 3: 3.652 V, Cell 4: 3.651V. I did not want to go through all 88 cells, but I suspect most of them are within 0.001 volts of each other. The pack voltage was 321.319V, divide by 88 and get an average of 3.6514 V. I bet I have one or maybe two cells that are more than 0.001 volts away from 3.651 Volts. The pack is at 36.0% SoC.
If the cells are this close, I wonder what delta V would case a complete shutdown?
2017 e-Golf LE, Multi Coat White with Black Vegan Leather interior

Clanch
Posts: 9
Joined: Thu Feb 20, 2020 1:08 pm

Re: Electrical system failure: Stop!

Sun Feb 23, 2020 9:16 pm

Found an interesting article online Inside EV. The Chevy Bolt, there early production problems with batteries. They had the same type of problems the 2015 egolf had. They recalled the cars, and loaded a new software version into them. The new software would give the customer advance warning of a potential battery problem, and if the threshold got worst would tell the customer you have diminished range and not shut off the car. it would inform the customer vehicle needs service immediately. Hopefully the customer would listen and not keep driving the car. OnStar system would also send out updates of the vehicle status and problems. Not a big Chevrolet fan but, kind of cool. Volkswagen are you listening?

Pargias
Posts: 1
Joined: Tue Feb 25, 2020 4:19 am

Re: Electrical system failure: Stop!

Tue Feb 25, 2020 4:24 am

I got the same problem yesterday with a 3 weeks old golf, just under 1500km. So apparently the problem is still going on… That's disappointing because apart from that I find it very nice to drive.

Szyszka
Posts: 70
Joined: Fri Sep 06, 2019 8:31 am

Re: Electrical system failure: Stop!

Tue Feb 25, 2020 6:59 am

It would be really, really nice if all the new users (Pargias, Dlmmdajgal, Poshnorris, spana123) who suddenly felt an urge to register and join the forum to only report about the error were kind enough to update their posts and told us exactly what the cause was and how the dealer addressed it. It is really not all that helpful to the overall community to simply report the error and not follow up to tell us what happened after the diagnosis was made...

Sorry, had to vent...
Pargias wrote:
Tue Feb 25, 2020 4:24 am
I got the same problem yesterday with a 3 weeks old golf, just under 1500km. So apparently the problem is still going on… That's disappointing because apart from that I find it very nice to drive.
Dlmmdajgal wrote:
Mon Nov 04, 2019 9:16 pm
Another 2019 with this message. Car's at Sunnyvale dealer waiting for west coast technician to inspect. The wait could be long.
Poshnorris wrote:
Thu Jan 02, 2020 11:13 am
My UK egolf came up with this message after an epic 31 miles from brand new. Luckily wasn't driving when the fault occurred but car wouldn't start and has been recovered to VW. They say it's the high voltage heater or a module connected to it and the part is being replaced. Hopefully this will be a true fix as I don't like the sound of the car cutting out when driving on the motorway!
Can anyone beat just 31 miles for total car failure?
spana123 wrote:
Mon Sep 16, 2019 1:20 am
Thanks for sharing
I also experienced failure of electrical system.

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