SamTexas said:
Agreed. "improperly used" was poorly chosen. But the problem is still with the BMS and NOT with the battery.
Though that is partially true, the fact remains that some of the batteries, almost certainy including that one of Lyen's, have cells that fail in a way that leads to this problem. If the BMS fails to detect the problem, then it's a poor design for that type of cell, but it still doesnt' change that the cell itself did fail in a way that leads to draining all the others in parallel with it. This is what happened in my own packs, and I suspect that if my BMS had not cut off the pack from use, the same thing would have happened to me--the cells would have reversed, heated extremely, and caused a fire. Might not have been the cells themselves burning, but it doesn't matter.
Of course, it could be said that it's *still* not the cell's fault, and that it is the fault of the pack builder for using flammable materials around it, rather than something that would not melt or ignite *when* cells failed in such a way as to heat up that much.
The logical conclusion would be to not buy a battery pack from that seller or to not buy any battery pack using that BMS.
I won't disagree with that conclusion, but it does not cover all of the problems discovered in that fire. It only covers the BMS's failure to detect a problem.
Also, remember that VERY few purchasers of these packs will know anything at all about them other than what the advertiser says about them (just like every other product out there), and most are not going to do any research on it, even if they knew how and knew what they were looking for.
Most sellers of such packs are not going to know what BMS is in there, even if you know what to ask. Some of them probably wouldn't tell you even if they did know, because it's too much work to answer questions like that, and they lose money spending time on people that ask questions. Very few ads that I have seen for packs say or show what BMS is in there.
There's also no list of which BMS causes what kind of problem, even here on ES, much less elsewhere on the web. Heck, I don't even know what kind of BMS is in the pack that caught fire--it's not actually in the thread itself, AFAICT in a very quick glance-thru, other than a pic of it still shrink-wrapped.
Another issue is that there's no way to know (before buying) which BMSs work in the same way as that one, to avoid them, even if we know that a particular pack uses a particular BMS (whcih as pointed out above is very hard to find out before you have it in your hands). The sellers don't know, and again: even if they did they may not tell you.
To repeat what several have already said: All energy storage systems have a certain level of built in danger. But that danger level varies from one battery chemistry to the next. The goal is to choose the right chemistry for the application with the lowest risk of fire and explosion.
Certainly. But since the actual risk is not *just* with the chemistry itself, but also with the support electronics working as needed to prevent the problems (without user intervention), it becomes very difficult to say which one is "safest".
LiCo, one of the most volatile of these chemistries, is *THE* most widely-used type in the whole world. It is in every class of device that I know of, except possibly UPSs, and is probalby used in those, too, somewhere. But the electronics are designed so that it (almost) never reaches conditions that cause the fires we have seen. Yet, it does still happen, in every class of device. Phones and laptops both have had videos on YT and elsewhere of simply suddenly bursting into flames, while in use or just sitting there charging.
The fires are much more common with the LiCo (LiPo) RC packs, but remember that almost no one that uses these packs is using them with such restrictive safety electronics, so that they can get much more useful capacity from them for their size/weight. Thus, they are more likely to end up in conditions that are unsafe, and they are usually charged and discharged at much higher rates than the other LiCo. Even if designed for that, it still changes the conditions enough that without the more severe restrictions on LVC/HVC, you wind up with more average occurences of excursions outside the safe range that then damage the packs, causing the fires during recharge or in use.
There are of course other contributing factors: LiCo RC packs are bought from the cheapest source by most poeple, regardless of known "quality problems", EVEN THOUGH THEY KNOW BETTER. Look around here on ES for many examples with HobbyKing.
LiCo consumer device packs are purchased by the major OEMs from the cheapest *safe* source--they are not likely to just go with the very cheapest stuff they can find, because they do know that there is a certain level of manufacturing quality and pre-screening required to get the dud cells out before they end up in something that could burn a house down. It does probably still happen from time to time, and you end up with problems like the Sony/Apple/etc battery recall of a few years ago.
Remember that I am trying to speak from the viewpoint of the average consumer, and not someone that has the experience that I actually do with batteries, as well as the things I've seen here on ES and elsewhere.
The average consumer doesnt' know a thing about batteries other than that they are inside many devices, and that sometimes they ahve to be recharged or replaced. Typically they don't even know *when* those things should be done, until the device either tells them to do it, or simply doesn't work anymore. :lol: This includes ebikes and EVs, and is one reason so many of us try to get noobs here to buy a wattmeter of some kind.
