Electrically there’s no need to insulate cells from each other within a p-group (where all the cells are already connected together and at the same voltage anyway).
Having wraps on can help insulate the cells from being touched though and adds another insulating layer on top, where the cell is most vulnerable to being short-circuited.
For anyone else reading this…you must insulate the p-groups from each other and the user!
This happened at my work, brand new charger and batteries. This caused cells to catch on fire and shoot across the room. We had just taken on a commercial account with this company.
The Damage was unreal. Fire sprinklers and all. Be very careful with these cells. Even in a protected environment
does that black stuff come off completely/easily? if rewrapped ideally id like the cell almost 100% clean
Were they shorted as they were charging?
On the positive side of the cell, yes, typically without any issues. The negative likes to be a bit more of a pain. Takes 2-3 minutes to clean medium covered cell, 5 or so minutes for a bad one just using fingernails.
I’m going to try to pick up a rubber or nylon wheel for a drill though to speed it up: https://www.reddit.com/r/AskMechanics/comments/12ea904/whats_the_easiest_way_to_clean_rtv_silicone_off/
would it peel off with something like goo gone? that stuff is amazing
Maybe? I have some at home I can test and report back on. I didn’t think about trying that
I have half a mind to by a two pack of the p42a packs.
I got 120 of their 2$ 30T cells. Not as good of a cell but they are in factory packaging, brand new, no work needed.
I like disassembling packs, but I hate the individual cell measuring/cleaning/checking/wrapping part.
No idea what happened, but that would be my guess.
Geeeeez!! Whaaaat on earth
well now that ain’t safe😂
Shorted? I’m not sure that’s the most likely scenario.
How would any of the cells get shorted while they were just sitting there being charged?
Was it the charger made for that pack?
If yes then things get mysterious IMO. A BMS failure could allow an overcharge but that needs a badly unbalanced pack and this was new.
Has the pack been dropped a lot or otherwise roughly handled?
Can confirm works well. One spray on the cell, leave for 30 seconds or so, then the majority of it scrapes away with a guitar pick without issue, and a quick wipe of a paper towel cleans the rest
These were basically new packs, about a week old. Highly doubly they were abused, but the possibility exists.
These were left charging unattended for a few hours. They were the flexvolt 20v packs. The tool company ended up paying for the entire repair and replaced most of the tools in the storage area that were damaged (not all from the fire, sprinklers got everything wet)
Purchased 2 of the robot batteries. Wish me luck, seems fairly straightforward. At 1.68 per cell shipped to me it’s hard to not try at least, for p42a
Damn it, I’m for two now.
Make a video! Id love to watch that!
I was thinking about it! No clue how much stock they have tho
@ShutterShock, You busy for the 4th of July? We could inadvertently do our own pyro show, or maybe they know 1 cool trick your local EE doesn’t want you to know to generate free energy. 
Perhaps I’m out of my mind but, if properly controlled (tape over the top to deflect debris) and safety precautions taken, then this seems to be a great way to remove the nubs.
Not necessarily with a hammer but perhaps manually? Better than taking a dremel to the top IMO. 
It can’t really damage the fragile and thin bottom contact and any method creates metal dust or fragments that need to be controlled.
Yea, the best option is to use new cells but salvaging cells will always continue to be done so anything that is a bit less dangerous or damaging could be good to consider.
