GM recommending customers park the Bolt fire machine 50 feet from others!

[AZBill]

It doesn't have to be so. There are barriers in place to prevent this runaway in most vehicles. Obviously in the Bolt this is not entirely working. It is not an accident that GM, sorry gm, main recommendation is to back off on the full charge and have a more robust reserve. That's the main problem. The lack of a robust reserve which allows the cells some wiggle room.

The backing off of the charge level is simply a means to reduce the risk, not to prevent fires. The last fire that occurred had the battery at 15% charge, and it had not been charged for several days.

All LG pouch cells use the folding technique during manufacturing. The Kona had a folded anode defect, uncovered by Hyundai. The Bolt has folded separator and torn anodes, uncovered by GM. Both Hyundai and GM tore down some sample batteries and found the defects, which were caused by the LG manufacturing process. Also, the Kona batteries were made in a factory in China, the original Bolt batteries were made in Korea and the latest Bolt batteries are made in the US. So LG has a manufacturing problem that appears to be everywhere. The Audi, VW, Porsche and Ford batteries are made in Poland, but only one fire has occurred in those so far.

Bolts had been out for over two years, before the first fire occurred.

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[leeman]

OH My

 

[theo1000]

The backing off of the charge level is simply a means to reduce the risk, not to prevent fires. The last fire that occurred had the battery at 15% charge, and it had not been charged for several days

The buffer problem exists counterintuitively at both ends! On the Etron Audi Engineers were more worried about the fires on the low charge end and left a 8% buffer on the low end! Compared to a 4%-2% buffer top end. And they advised you not to leave the car discharged for very long. Its the leaking electrolyte that catches fire not the charged electrons!!

Also that may just have been when the problem was detected. Same used to happen to the Volt when the car would very occasionally catch fire long after an accident. Sometimes months later.

I'm not even certain there is a manufacturing problem. Per the NHTSA the error rate is 1 in million+ cells! That is 7 sigma. No too many products work at that error level. The real issue was that they don't have a QC procedure that works to weed out the problem cells. I'm sure they are feverishly working on some form of non-destructive penetrative radiation based imaging that will allow them to eliminate 100% of the defective cells. I can't imagine anyone trying to address that low error rate. Again things gm won't tell you....

I stand by what I said. The poor buffer gm worked into their design is an issue that gm is not addressing. The Audi Etron engineers specifically said that the large buffer is there to improve battery life and safety.

There is one other company that also runs a very low buffer and sees an inordinate number of fires. And I'm not talking about the Kona EV which has a 3 kwh or 4% buffer and has also had a recall due to fires.

 

[AZBill]

The buffer problem exists counterintuitively at both ends! On the Etron Audi Engineers were more worried about the fires on the low charge end and left a 8% buffer on the low end! Compared to a 4%-2% buffer top end. And they advised you not to leave the car discharged for very long. Its the leaking electrolyte that catches fire not the charged electrons!!

Also that may just have been when the problem was detected. Same used to happen to the Volt when the car would very occasionally catch fire long after an accident. Sometimes months later.

I'm not even certain there is a manufacturing problem. Per the NHTSA the error rate is 1 in 12 million cells! That is 7 sigma. No too many products work at that error level. The real issue was that they don't have a QC procedure that works to weed out the problem cells. I'm sure they are feverishly working on some form of non-destructive penetrative radiation based imaging that will allow them to eliminate 100% of the defective cells. I can't imagine anyone trying to address that low error rate. Again things gm won't tell you....

I stand by what I said. The poor buffer gm worked into their design is an issue that gm is not addressing. The Audi Etron engineers specifically said that the large buffer is there to improve battery life and safety.

There is one other company that also runs a very low buffer and sees an inordinate number of fires. And I'm not talking about the Kona EV which has a 3 kwh or 4% buffer and has also bee plagued with fires.

I agree buffer affects battery life, but this is a physical defect that causes a short. Torn anode touches cathode due to folded separator. Normal expansion and contraction during battery discharges and charges aggravates the issue. There have been 20 fires in 140K cars, that is not 6 sigma, let alone 7 sigma. VW has a bigger buffer and one of those just lit up.

 

[theo1000]

I agree buffer affects battery life, but this is a physical defect that causes a short.

But the cars are not all catching fire immediately right. So it is more than that. The more data that comes out the more I'm certain its the buffer.

All my EV's from LG cells, Volt, Audi, MachE, have large buffers and don't seem to have similar issues. My I3 with prismatic cells has an incredible 25% buffer. Very low fire incidents. It will never be zero mind you. With a large buffer the rate drops so low, the design can tolerate some level of defects.

I bet if gm permanently backs off the usable charge to say 55 kwh form ~62 kwh at present the issues will disappear almost overnight.

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