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| Panasonic NKY467B2 36V 15AH 540Wh. Ebike Li ion upgrade, burning my father'ass? |
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| MT:
--- Quote from: Siwastaja on October 11, 2018, 04:45:15 pm ---External heat over the thermal runaway onset temperature - around 150 degC - would be the best bet, since the modern shutdown separators seem to work so well that even a nail penetration is not setting these things on fire anymore. Warning: this is not to say you should abuse the cells in any way. They can catch fire because the inherent chemistry is still very volatile - it's just got safety layers built around it -, and abusing them will of course increase the risk as it puts more burden on the safety features that are not "normally" needed. It's just that it doesn't tend to usually happen, because the safety features are well designed. --- End quote --- Thanks for your efforts to describe issues with LiPO's BMS etc, most interesting, but i wonder when in time did LI cells get this protection from nail penetration ,overheat regulation , shutdown separation, etc? Just recently? is there a definitive date to it so one can distinguish old from new tech? |
| Siwastaja:
--- Quote from: MT on October 15, 2018, 08:29:19 pm ---Thanks for your efforts to describe issues with LiPO's BMS etc, most interesting, but i wonder when in time did LI cells get this protection from nail penetration ,overheat regulation , shutdown separation, etc? Just recently? is there a definitive date to it so one can distinguish old from new tech? --- End quote --- There is no definite date, it has gradually got better over the whole three decades of commercial li-ion history. Cells from the Big Guys (Sony, Panasonic, Sanyo; later Samsung SDI, LG Chem...) have always been fairly safe, except for small issues every now and then, which then drive the safety culture forward. I think everybody's had their share of issues as well. Most of us still remember the Samsung smartphone fires around a year ago? (It was two separate incidents with two different cells, with two completely different failure modes; only the latter being a Samsung SDI cell IIRC.) Sony had laptop battery fires in early 2000's as well. Using any currently available cells from the big, trusted brands should be OK, even if you find some recent-ish new old stock. AFAIK, there are no big safety breakthroughs in production cells during the last decade, just some gradual improvement. I'm sure shutdown separators, PTC endcaps and CID rupture valves have been standard parts of proper 18650 cells for over a decade. While the new (current) NCA and NMC cathodes are arguably safer than the "old" LCO (still available commercially, but getting niche), the difference is fairly small. I think it's something like a 10 degree C difference on the thermal runaway onset temperature, and some tens of percents less energy in said incident... The cathode safety order would be something like (from the worst to the best), 4.35V LCO, 4.20V LCO, NCA, NMC, LMO, LFP, LTO. I tend to trust 18650 cells more than pouch cells. Nail penetration and crushing can never be guaranteed 100% safe given the current technology, even though they are tested and typically don't result in a complete thermal runaway. We all would like to see some real safety breakthroughs, for example, a cathode that doesn't run away thermally at all, or nonflammable electrolytes, but AFAIK they are not in the horizon. Remember that 99.99% of the battery science "breakthroughs" you read about in the media (traditional or even specialized tech media), are either complete scams, or massive exaggerations trying to lure in investor money. But, real 0.01% breakthroughs do happen given enough time and resources. |
| MT:
--- Quote ---Nail penetration and crushing can never be guaranteed 100% safe given the current technology, even though they are tested and typically don't result in a complete thermal runaway. We all would like to see some real safety breakthroughs, for example, a cathode that doesn't run away thermally at all, or nonflammable electrolytes, but AFAIK they are not in the horizon. Remember that 99.99% of the battery science "breakthroughs" you read about in the media (traditional or even specialized tech media), are either complete scams, or massive exaggerations trying to lure in investor money. But, real 0.01% breakthroughs do happen given enough time and resources. --- End quote --- Speaking of material tech in this fairly recent video Andreas Hintennach; Chemist ,MD, PhD, Daimler AG, Mercedes-Benz, Group Research, Germany talks about post lithium materials such as sulfur and soldistate ceramics etc. https://youtu.be/pxC2pciLl04?t=19 Mr Goodenough debunks Tesla batter management system, talks further on solid state battery techniques. |
| Siwastaja:
--- Quote from: MT on October 16, 2018, 01:05:28 pm ---Mr Goodenough debunks Tesla batter management system --- End quote --- No he doesn't - debunking means giving some factual representation with solid arguments. His arguments can be easily fact-checked. Does the Tesla's pack last only for two years, after which it needs a replacement, and is it true that the Tesla owners are all happily buying these replacements after just two years? Is Tesla's battery management system as expensive as the cells themselves? I think we all know the answer to the both questions. Especially the first one is easy. The second one might fool someone. I have closely looked at the Model S hi res battery teardown photos. The BMS system is very typical, simple, and doesn't look too expensive. It has fairly low-current dissipative balancing, for example. Of course, if you count the Tesla's thermal and shock management as "management" as well, which could be fair, then this claim isn't necessarily too far from the truth, so maybe it's politician-class "stretched truth" - something which IMO doesn't belong in science nor engineering. Anyway, Tesla's liquid cooling system has a lot of bent pipe in it and it does definitely cost something. I still doubt it's as much as the cells are. But I'm sure getting rid of it by having more robust battery tech would allow quite some savings! As we all (should) know, "managing" 100 cells in parallel is basically no different to managing one cell. Managing 7000 cells is not 7000 times more complex nor expensive to managing 1 cell. --- Quote ---, talks further on solid state battery techniques. --- End quote --- While a big name in the industry history, Dr. Goodenough has lately been on public several times basically marketing certain technologies or certain companies. While this gives the discussed companies and technologies more credibility, it doen't guarantee much about how viable they are. We all want to get rid of that flammable liquid electrolyte. But, I do believe that some novel way will eventually succeed and make an actual breakthrough. People close to me (relatives and friends) knowing my work around battery tech, I get a lot of links of "look at this battery breakthrough!" on media, and I'm a bit tired about all of it :). So I'm sceptical by default, and even Dr. Gooenough isn't much of an argument in my view; I'm not a believer in authority anyway. BTW, there is an important distinction between the battery engineers, and battery system engineers. The former - the chemists who design the cell technology - often don't like the idea of needing a BMS, and eagerly develop a cell which won't need one. The latter type, most of the time, tends to be huge believers in BMS systems, and are actually very happy with all their complexity, unreliability, etc., since that's what giving them their jobs. I share the battery scientists' sentiment there, and I would very much like to see a robust and simple cell. |
| MT:
--- Quote from: Siwastaja on October 16, 2018, 03:12:03 pm ---No he doesn't - debunking means giving some factual representation with solid arguments. His arguments can be easily fact-checked. --- End quote --- Well, perhaps not debunks but laughs! :) --- Quote ---Does the Tesla's pack last only for two years, after which it needs a replacement, and is it true that the Tesla owners are all happily buying these replacements after just two years? Is Tesla's battery management system as expensive as the cells themselves? I think we all know the answer to the both questions. Especially the first one is easy. The second one might fool someone. --- End quote --- Then Mr goodenugh is not goodenough to Tesla. --- Quote ---I have closely looked at the Model S hi res battery teardown photos. The BMS system is very typical, simple, and doesn't look too expensive. It has fairly low-current dissipative balancing, for example. --- End quote --- Is is a safer one or one of those TI etc chip based unsafer ones? --- Quote ---Of course, if you count the Tesla's thermal and shock management as "management" as well, which could be fair, then this claim isn't necessarily too far from the truth. Tesla's liquid cooling system has a lot of pipe in it and it does definitely cost something. I still doubt it's as much as the cells are. But I'm sure getting rid of it by having more robust battery tech would allow quite some savings! --- End quote --- I dont he specifically talked about crash management just in general. --- Quote ---As we all (should) know, "managing" 100 cells in parallel is basically no different to managing one cell. Managing 7000 cells is not 7000 times more complex nor expensive to managing 1 cell. --- End quote --- Do Tesla refurb, replace individual defunkt cells or just offer entire new banks/plates when a customer get battery problems? --- Quote ---While a big name in the industry history, Mr. Goodenough has lately been on public several times basically marketing certain technologies or certain companies. While this gives the discussed companies and technologies more credibility, it doen't guarantee much about how viable they are. --- End quote --- Perhaps its more for him to push the paper and tests they published with the Portuguese scientist who invented that ion carrying glass or something. --- Quote ---But, I do believe that some novel way will eventually succeed and make an actual breakthrough. People close to me (relatives and friends) knowing my work around battery tech, I get a lot of links of "look at this battery breakthrough!" on media, and I'm a bit tired about all of it :). --- End quote --- Dont despair R/D is inevitable! Your friends dont know as much about battery they just want to rid themselves of oily arabs, russians, americans and norwegians! |
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