Except that people on ES keep recommending reconfigurable lipo packs as a way to power ebikes...Alan B wrote:In the Floont case he was reportedly reconfiguring a number of different packs together to very high voltage and bulk charging them, so the balance was poor, and not monitored or controlled. This is a particularly high risk approach to battery configuration, and I would not recommend that.
I'm working on a survey of battery fires I can find, and the vast majority of them involve hobby lipo packs. I'm having a genuinely hard time finding fire reports from other battery pack types - and I know there are a lot of other batteries out there, but they just don't seem to be catching fire like the lipo packs.
As far as house fires/car fires/other structure fires, RC boards are an endless supply of them as well. Admittedly, their power sources are almost entirely hobby lipo packs, so I'd expect the bulk of the fires reported there to be hobby lipo based, but there are an awful lot of torched houses & cars as a result of them, not just on ES.
If you've got a million random wires and connections running around, yeah, you've got a lot of opportunities for shorts inside the pack, and the heat released will generally melt insulation and cause more shorts (or just straight up thermal runaway of neighboring cells). This doesn't seem to be the case in many 18650 packs - there isn't a way to get multiple shorts going, and a battery failing will often not be able to get the surrounding cells up to thermal runaway temperatures, so the energy released is a single, decently cooled cell (heat flowing into other cells rapidly enough that it doesn't get up to ignition temperatures).For high current applications the BMS is not generally switching the high current path, it controls power to the controller logic subsystem instead, so a short will depend not on the BMS but on the overcurrent device which many builds are lacking, or which are not rated for the proper voltage. This only works if the short is downstream of the protective device. The majority of connections and opportunities for a short are inside the battery pack where the overcurrent device or BMS is not helpful.
This is certainly a problem. I think the reality is more that they're too expensive for people to want to spend money on for their 6kW ebike. That's fine, but if I can shift attitudes such that only the truly high powered bikes are using lipo packs, it's still an improvement. You don't need them for a 1000W commuter.Not many commercial packs meet the needs of high performance ebikes. They cannot deliver the current needed. Or they are too large, heavy or expensive for the application. If folks could easily and cost effectively buy packs that met their needs, they would. They just aren't very available in the configuration that fits the application.
And if the DIY people continue to make fireball ebikes that burn down buildings, it's going to very negatively affect public opinion of ebikes.The people on this forum don't represent the majority of ebikers. These are the folks who want to build something, not the off-the-shelf appliance operators that represent most of the population. Not too many of this crowd live in apartments, from what I've seen. If you want to address the majority of ebikers you need to find a different venue. This isn't going to reach them. This is the DIY crowd made primarily up of engineers, technicians, inventors, experimenters, modders and tinkerers.
Though I will grant you, very few people here seem to be burning things up in apartments. I'm not sure why that is, but I have noticed that.