Thursday, December 8, 2011

The Volt Battery Issue, Much Ado About Nothing

The media and the anti EV crowd have been getting quite worked up lately about the Chevy Volt battery pack and perceived yet unrealized dangers from fire.  Two Chevy Volts were parked in garages that happened to burn down, just as happens to many ICE vehicles every year, yet in the Volt cases blame was automatically placed on the hybrid vehicles, presumably because they are something new.  However in both cases the Volts and their batteries were found not to be the source of fires.
Then in May NHTSA ran a side impact test on a Chevy Volt.  This test consists of sliding a vehicle sideways into a solidly mounted pole which totals the vehicle.  The Volt passed the test for occupant safety.

Three weeks after the test, which damaged the battery pack, the pack caught fire.  (Interestingly when the same test is done on conventional ICE vehicles the tank is drained, probably because NHTSA doesn't want gasoline flying all over it's facilities.)  This seemed to be an isolated incident as other tests done by other organizations did not result in any fires.  To further investigate NHTSA ran more tests on Volt battery packs, bare packs not in a vehicle.  The packs were penetrated, further than in the original crash test, then rotated to simulate a rollover.  In the first test nothing happened.  In a second test there was a temporary temperature increase initially, then a week later this pack caught fire.  In a third test the pack smoked and sparked but did not catch fire.  At this point it seems that leaking coolant for the batteries can cause some short circuiting if the pack is not drained after a severe accident.  There have been no fires in actual use during a crash of the Volt, and NHTSA considers the Volt to be a safe car which has a 5 star crash rating.  GM is working on some upgrades which will further protect the pack and address this battery issue which would only happen in extremely rare circumstances.
There are over 200,000 vehicle fires a year in the US, all of them ICE vehicles, yet because the Volt is a new product people are trying to paint it as more dangerous than it really is.  Any vehicle has risks, any energy storage container, be it battery or fuel tank, has the potential for mayhem, and nothing can be made completely safe.  However, in the real world, the Volt has proven to be safer than most other vehicles on the road, and with the planned upgrades it should be safer still.  I'd be much more concerned with the Volt's gas tank in a crash than it's battery pack.  The LEAF, an EV with a larger, but air cooled battery pack, has had no issues in any crash test or real world accidents.  Nor have any of the crashed Tesla Roadsters, with even larger yet liquid cooled packs.  At this point EV's are proving to be statistically safer than ICE vehicles, as I would expect, and that trend is likely to continue.

Coolant cause of shorts
Battery Upgrades
Vehicle Fires


  1. BS. GM is publishing this crap to cover their ass. The damage is caused from the shock and not the water crystalizing on the cells. Total BS.

    My Mac hit the floor and still continued to work. Only visible damage was to the outside case in the corner which got bent when it hit the floor from 4 feet up. It was a hard hit but the computer protected the hard drive and mother board just fine as well as the screen. The battery had no visible damage what so ever but over a period of 4 months the battery slowly started to run warm and with less capacity and it also began to slowly swell. If it had not been caught it could and most likely would have burned down the house. When it was noticed that it was running hot it was actually too hot to touch but the battery still provided power to the computer. It was the SHOCK to the battery that ruined the battery and nothing else. A hard side impact would provide such a shock and the damage would not be seen. Having tested with a full battery pack was actually what was needed. It was needed to show that a shock can still ruin a battery.

    Sorry but it is much to do about a whole bunch and not about NOTHING.

    The coolant did not catch fire, but crystallized and created an electrical
    short that apparently sparked the fires, said the person, who asked not to be identified because the findings are not final.

  2. This is total BS.

    The coolant did not catch fire, but crystallized and created an electrical
    short that apparently sparked the fires, said the person, who asked not to be identified because the findings are not final.

  3. Its a GM angle. Lies Lies and more Lies. When will you learn.

  4. You're buying into Jack Rickard conspiracy theories. NHTSA is not GM and they are not covering up anything. Of course the damage is from the impact, no one claimed otherwise.

  5. @GreenEV: Are the batteries in your laptop the same type as used in the Volt? If they are like the ones in a couple of MacBook batteries I took apart they aren't. The MacBook had LiPoly batteries. I thought the Volt had LiMn based batteries. Just as it isn't wise to assume that LiFePO4 batteries are just like lead acid batteries, there isn't a straight across comparison between the different types of Li cells. Furthermore, in the MacBook batteries it took apart I can see how just the right shock could cause the aluminum case to contact the pouch of the cell and penetrate the insulating layer thus causing a short. The BMS might also have an issue and end up draining the cells or not charging them the same. There is a separate wire to each cell which goes to the internal circuitry in the battery pack. This wire is quite thin and separate from the ones which power the laptop.

  6. You're right of course that the Volt cells are probably not the same as the MacBook cells, though they are both LiPoly, but different chemistries. Volt does use LiMn but they are of the LiPoly construction, where I think most LiPoly are LiCo based. Regardless there is no doubt that the Volt cells were penetrated, but unlike most LiPoly cells I've seen did not catch fire or explode immediately. The Volt coolant is conductive and can cause short circuits given enough time.

  7. I do not believe that the packs were penetrated either. I think it was only the shock that caused the damage. I do not buy the coolant leaking and then drying then causing a short. That would only drain a cell. Those packs are built pretty stout. Until they come out and say and show that the pack was penetrated then I hold my ground. Any coolant can be conductive but unless a cell was penetrated or shocked hard enough I do not thing you'd get anything but a drained battery. I do not believe that a little dried coolant could or would be conductive enough to allow such a large amp draw to cause the cell to go into thermal runaway. Maybe enough to slowly drain and just empty the cells.

    No I do not think that the cells are exactly the same but they are not LiFePO4 either and all the oxide type cells have a similar chemistry and reactions. I was using the the lap top issue as a way to show that shock damage can cause an internal shorting that can cause damage and enough damage to ruin cause over heating and swelling even over time.

    Pete :)

  8. So what you are saying is that both NHTSA and GM are blatantly lying. Ridiculous. The cooling plates are between each cell, it only takes a couple of inches of penetration to puncture both the cells and cooling plates. A simple shock to a cell with no penetration is unlikely to damage it in this way. Subsequent tests by NHTSA took bare battery packs, removed from the vehicle, and penetrated them to try and recreate the problem, which they did. Also, the proposed fixes developed by GM would do nothing to prevent a shock problem as you describe and in fact are intended to mitigate problems from penetration. Your insistence on ignoring the evidence in favor of some unlikely scenario is puzzling. Some people like to make up conspiracy theories instead of seeing the simple and obvious truth I suppose.

  9. Regardless of what caused the fire, it makes sense that if an EV were in an accident that the battery pack should be checked out ASAP. If there is obvious physical damage then it should be removed from the vehicle and appropriately dismantled. I don't know what the damaged Volt pack looked like and how easy this would be to do. Maybe all it would take would be a simple load drawing maybe 1000W to drain the pack in a day. There would then be less energy left to cause a problem.

    If the pouch cells used in the Volt are constructed as layers rather than a rectangular spiral then I can envision how a shock to a cell has the potential to cause an internal short. I don't understand, however, why it would take 3 weeks to show up. Maybe it was a low current leak which couldn't dissipate the heat.

  10. I think you've pointed out why it was not a shock induced internal short that caused the fires, it would have shown up a lot sooner than three weeks. However leaked coolant might take that much time to dry out, crystallize, and then cause the short. Plus the fact that NHTSA said the pack was penetrated and then did three other penetration tests, not shock tests.
    As for draining a damaged pack, that may or may not be a good idea, since pulling current from a damaged pack might actually cause a problem. Id' say the first thing would be to remove a pack from a vehicle, then assess and proceed from there.

  11. The batteries in the Volt are of similar chemistry as those found in laptops, and indeed the ones that have caught fire.

    As numerous videos on YouTube have demonstrated, lithium oxide batteries pose a serious (not to mention fast spreading) fire risk when damaged and thus have no place in automobiles.

    Lithium phosphate batteries are nowhere near as energetic when damaged. This is because the concentrations of available oxygen are much lower. They heat up, they smoke a lot when venting, but do not violently burst into flames like lithium oxide batteries.

    Some of my very first research into EVs online lead me to YouTube, where everyone in the world can see the destructive tests between lithium oxide and lithium phosphate cells. Those videos immediately impressed upon me the dangers of lithium oxide cells, and the idea of putting them in a car likewise immediately left my mind forever.

    I just find it hard to believe no one at GM or Nissan or any other OEM has visited YouTube. SOMEONE must have said to themselves, "Gee, what happens if these cells are ruptured in an accident?"

    I consider it to be very foolhardy for anyone to even consider buying an OEM electric (or even hybrid) vehicle without first ensuring that lithium oxide cells were not used in its construction. Personally, I'm glad this problem is occurring, and being made public, so that hopefully the OEMs will stop producing EVs with lithium oxide cells.

    @Gizmo - My best guess is three weeks is about how long it takes for enough moisture to invade the exposed cell(s) and react with the lithium. Then it builds up enough heat to cause the cell to burn (YouTube, "lithium and water reaction"). Finally the single cell fire cascades into the other cells. Poof, toasty.

  12. The problem with that analysis is that as I've pointed out and you have just reiterated some LiPo cells react violently when punctured, yet that is not what happened with the Volt. It took weeks for the first event to happen, and a week for the other test pack to catch fire. That is not what is seen on the youtube videos that react immediately, without the introduction of moisture. Yes oxide cells can react more than LiFePO4 cells, yet not all of them do. That's because there are construction methods that can mitigate that potential. There are also youtube videos of oxide cells being punctured with no reaction at all. The fact is that oxide cells can have about twice the specific energy density as LiFePO4 cells which allows greater range. Tesla has been using LiCo cells for three years now with zero events, even in severe Roadster crashes. There have also been no fires in any Volt's in the real world.
    Yes oxide cells have a greater potential for reactive events than LiFePO4 cells, but that risk is still very minimal, don't be fooled by some youtube videos of cheap hobby cells.

  13. All this hoopla about fires that are almost impossible to replicate in the real world due to time constructions. Here are facts about real fire hazards, many deaths!

    There were 215,000 vehicle fires in the U.S. last year, and yes, only 3% were caused by accidents.  But, 72% were caused by mechanical or electrical failure.  What does this mean?  The possibility of spontaneous combustion.  Is this not what Volt haters have been calling this poor little car?  You can be driving down the road and your car can combust!

    Ford had a major recall in 2009 for 4.5 million cars.  There were 550 reported fires and quite a few homes were lost.  These cars DID spontaneously combust.  It is suspected that many fires were not reported for various reasons.  

    One fire in a garage that the fire marshal emphatically states was not the Volt's fault and the sky is falling!

    Here are some recalls.  One involves 250 deaths due to fire!  Let's get real people.

    Ford recall:

    October 2011 recall of Audi and VW vehicles for possible fire

    Honda recall for some models for for some reports fires in the REAL WORLD

    Honda recalls more than 600,000 vehicles for fire hazard.,2933,584277,00.html

    More than 250 deaths attributed to Jeep fires in some older vehicles.  No recall as of yet.

    BMW is recalling some models due to fire hazards.