i don’t think it was due to the cells shorting due to the pos and negative shorting on the positive side of the cell, since we have heat shrink and the insulation ring underneath that would protect from such situations , tho that doesn’t mean it’s impossible
i’ve no clue what it’d really be, we’ll never know for sure
but my guess would have to be the bad contacts flexing, causing cells in parallel to jump in and out, causing more stress and increasing imbalance, and then cascading cause cells just keep dumping current to the point of thermal runaway,
but i’m a cat, or a piece of toast so take my thot with a slab of salt
Having looked at the structure of how the trampa’s pack structure was stacked, I’m pretty sure it has an inadequate clamping force, specifically in high vibration/impact use case (probably works no problem in lab testing on a table, as did mine), which would cause the same kind of short contact disconnections to happen and would cause an arc to form, which then in repeated fashion will start to build up soot from from the vaporized metal and possibly start to cause pitting as material is blasted away from the terminal, which then causes the terminal to become very un-even, which against the Trampa’s flat bottomed contact will then not be able to make as good of a contact.
This then in overall degrades the contact quality, leading to much higher contact resistance, which will then lead to extra heat as current is moved in during charging/regen and out during discharging, which can lead to a specific cell overheating and experiencing a thermal runaway.
All cells are captive, meaning they can’t be removed without something breaking mechanically, but there isn’t a holder per say. It’s a very simple solution mechanically.
Im using 21700 cells, the positive is aluminium, im in the process of building my first pack using this cell, i dont have an ultrasonic welder, im not soldering or spot welding the positives, i have come up with a solution but its takes me to long, the honey combe design is very appealing to me as space is always limiting, im building 30s8p 20s13p 20s6p a weld free design would be ideal aslong as its compact i have around 1000 of these cells, i can send measurements of pack dimentions i need
Someone has made a whole consumer product out of this idea. Anyone have any insider info? If nothing bad, I’m tempted to try this and see if it fairs better than Simo’s design…
