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OK, from the horse's mouth: http://www.faa.gov/news/press_releases/news_story.cfm?newsId=14233 http://www.faa.gov/news/press_releases/news_story.cfm?newsId...

OK, from the horse's mouth: http://www.faa.gov/news/press_releases/news_story.cfm?newsId=14233 http://www.faa.gov/news/press_releases/news_story.cfm?newsId... And here's a good document dealing with Lithium-Ion battery hazards: http://www.nfpa.org/assets/files/pdf/research/rflithiumionbatterieshazard.pdf http://www.nfpa.org/assets/files/pdf/research/rflithiumionba... I have a lot of experience with Lithium Polymer batteries as I fly eletric-powered radio-controlled helicopters and planes that use them. There are always reports of LiPo (as they are commonly known) packs puffing-up and sometimes catching on fire and even exploding (more like the popping of a pop-corn bag except that you have flames shooting out of it). I have personally exploded a small 3S (three cells in series) pack just to see the mechanism and the magnitude of the effect. I have to say that it took a LOT of work to explode the pack. I over-charged it to a ridiculous degree. Now, of course, there are also reports of packs catching on fire for no apparent reason at all. There are many explanations out there. The best I came across was from a PhD Chemist who explained it something like this (paraphrasing, of course): When these batteries are assembled there's moisture in the surrounding environment. And, while moisture is kept in check, some of it stays in the pack. They can't run a super-dry environment because it could be very dangerous. One of the electrodes is lithium-oxide infused in carbon. Lithium reacts with water, which gives you hydrogen. Carbon reacts with hydrogen to give you methane. As methane is generated the cell puff-up. If thermal runaway is triggered through other mechanisms and the methane ignites: kaboom! I keep about thirty LiPo packs in strong locked and vented steel container (heavy toolbox) in the garage away from flammable materials and flame sources. When we go to the flying field the same container is used to transport to the field. While at the field the container is always locked and, if possible, removed from the car. I have never had an incident I did not cause. As far as the Boeing issues. Hard to say from the outside. It could boil down to quality issues at their battery supplier. It is probably impossible to perform a full inspection on these kinds of batteries on delivery. How do you determine if there's too much moisture inside a sealed package?

refurb 14y ago
I think your PhD chemist needs to rethink his theory. Lithium oxide is not the same as lithium metal. Lithium metal reactions with water to create hydrogen and heat, but lithium oxide is a salt. It generates no hydrogen when it contacts water, but it might generate some heat. Carbon will react with hydrogen to give you methane, but not with the conditions inside the battery. You need a ton of pressure, heat and some catalyst to do that. After reading the wikipedia article, apparently the cathode can actually produce oxygen which may explain the bursting of the cells.
- robomartin 14y ago
  Well, let's blame me for not recalling the details of the conversation. I'm sure what he said was correct, which probably isn't exactly what I posted.
gtani 14y ago
I have never had an incident I did not cause. Probably not what you meant
- robomartin 14y ago
  What I meant was that whenever I've had a LiPo failure it was always traced to something I did. I have never had a pack spontaneously fail in any way.
sounds 14y ago
Hobby RC flying is fun! If you haven't watched them doing it, go on a weekend to one of the parks near you where hobbyists gather and just watch... only be prepared to get hooked. Back on topic: lithium-chemistry cells are known for their potential to explode for good reason. It doesn't have to happen very often before the bad press really kicks into gear. This is unfortunate, as lithium is really a pretty good foundation for green energy initiatives like electric cars. If the bad press really gets bad enough even cell phone and laptop batteries could become significantly more bulky and less powerful, just "for safety." Lithium cells can explode when overcharged – a tightly controlled charger is a must. (This is most likely what happened on the 787, though no official sources are out yet.) Lithium cells can also catch fire if the cell voltage drops too low. Cell voltage is a measurement of the amount of energy stored in the cell. The wikipedia page is a good place to start, but the practical effect of this is that the cell _must_ have a good regulator at all times! The same regulator circuit can do charging and discharging; that's how cell phones and laptops work. Hobbyists commonly use a ground-based charger/discharger for when the cells are not in use and a very small circuit on the vehicle. The voltage on a lithium cell drops much faster as the cell approaches empty, so the protection against too deep of a discharge must be sensitive and react quickly.
- robomartin 14y ago
  There's another way to think about this. There are probably billions of Lithium-based batteries in circulation world-wide. Yet, the reports of fires are few and far between. RC use is not a measure of safety because of the extreme nature of the usage. For example, I have a high-performance glider that draws in excess of 120A for rocket-like climb to altitude. Yet, those battery packs are a few years old and have never given me any problems. I don't know what the 787's issues might be. My money is on a quality problem at the battery manufacturer, not Boeing.

refurb 14y ago

I think your PhD chemist needs to rethink his theory. Lithium oxide is not the same as lithium metal. Lithium metal reactions with water to create hydrogen and heat, but lithium oxide is a salt. It generates no hydrogen when it contacts water, but it might generate some heat. Carbon will react with hydrogen to give you methane, but not with the conditions inside the battery. You need a ton of pressure, heat and some catalyst to do that. After reading the wikipedia article, apparently the cathode can actually produce oxygen which may explain the bursting of the cells.

robomartin 14y ago
Well, let's blame me for not recalling the details of the conversation. I'm sure what he said was correct, which probably isn't exactly what I posted.

gtani 14y ago

I have never had an incident I did not cause. Probably not what you meant

robomartin 14y ago
What I meant was that whenever I've had a LiPo failure it was always traced to something I did. I have never had a pack spontaneously fail in any way.

sounds 14y ago

Hobby RC flying is fun! If you haven't watched them doing it, go on a weekend to one of the parks near you where hobbyists gather and just watch... only be prepared to get hooked. Back on topic: lithium-chemistry cells are known for their potential to explode for good reason. It doesn't have to happen very often before the bad press really kicks into gear. This is unfortunate, as lithium is really a pretty good foundation for green energy initiatives like electric cars. If the bad press really gets bad enough even cell phone and laptop batteries could become significantly more bulky and less powerful, just "for safety." Lithium cells can explode when overcharged – a tightly controlled charger is a must. (This is most likely what happened on the 787, though no official sources are out yet.) Lithium cells can also catch fire if the cell voltage drops too low. Cell voltage is a measurement of the amount of energy stored in the cell. The wikipedia page is a good place to start, but the practical effect of this is that the cell _must_ have a good regulator at all times! The same regulator circuit can do charging and discharging; that's how cell phones and laptops work. Hobbyists commonly use a ground-based charger/discharger for when the cells are not in use and a very small circuit on the vehicle. The voltage on a lithium cell drops much faster as the cell approaches empty, so the protection against too deep of a discharge must be sensitive and react quickly.

robomartin 14y ago
There's another way to think about this. There are probably billions of Lithium-based batteries in circulation world-wide. Yet, the reports of fires are few and far between. RC use is not a measure of safety because of the extreme nature of the usage. For example, I have a high-performance glider that draws in excess of 120A for rocket-like climb to altitude. Yet, those battery packs are a few years old and have never given me any problems. I don't know what the 787's issues might be. My money is on a quality problem at the battery manufacturer, not Boeing.