I hadn’t heard of heatsinking for safety
1 Like
That heat sink is incredible. Amazing what they did with aluminum.
laughs in ventless lishen cells
1 Like
Maybe I misunderstood the point then, I was under the impression that the vent only comes into play once the cell is in thermal runaway, which I thought, was an unstoppable thing
But once a cell is in runaway, isn’t the entire pack as good as gone
The vent, along with the CID and PTC internal protection devices, is a critical part of trying to prevent thermal runaway from ever starting. It certainly plays a role once the cells goes into runaway as it offers a controlled release of everything into known directions (so the pack can be designed around that) but it is designed to release at internal pressure levels well below what’s seen during runaway.
You are definitely correct about thermal runaway being essentially unstoppable once it has started. Only by bringing the cell down to below the runaway threshold temp can you stop it before it burns itself out. This can be done using lots of water or aqueous firefighting solutions but that is not easy to do.
It depends on the cells and the pack and definitely isn’t guaranteed. It all depends on how hot the other cells get. If the first cell vents up and out then the heat can only come from the cells touching. If there is even a small air gap and/or there is insulating material between the cells then the other cells can be prevented from getting hot enough to go into runaway.
If the “rocket engine” spray of hot stuff from a cell in runaway is directed down and onto the other cells, as what a typical esk8 pack is basically designed to do because of the sheets of nickel, then full pack runaway is much more likely IMO.
Pack thermal runaway potential should be a huge part of pack design if we are concerned about safety but it means doing cell inter-connecting differently. That just won’t be changed IMO as it’s too convenient to use nickel sheets and, luckily, full pack incidents are fairly rare.
2 Likes
Well dang fells. Now you got me all worried about my 14s7p, I for sure welded anywhere I dang well pleased when I was making that pack
Add insult to injury…I even make spotwelded series connections 
Going to crack it open tonight to do a nose test 
what’s this leaking lithium supposed to smell like?
1 Like
Kinda sweet n chem smell. If u smell it you’ll likely realize. And liquid will likely come out too I think. Clear n thin
1 Like
The solvents in the electrolyte have sort of a sickly sweet “paint thinner” type of odor…very solvent-like, very strong. The lithium salt dissolved in the electrolyte doesn’t smell AFAIK. The electrolyte has a very slippery feel to it too, nothing like water.
Don’t touch it if possible though and only take tiny whiffs.
1 Like
That’s how it starts Mooch… And before you know it you are on a cell a day. Taking giant sniffs to go to sleep or before you go to work.
10 Likes
I just keep a stack of old evolve packs in the workshop. 24/7 fumes on tap
3 Likes
Even if it’s not a vented cell, you shouldn’t weld directly in the center of the negative terminal because that’s where the negative tab connects internally, and you don’t want to weaken that spot.
2 Likes
One cell a day? Why do you think I test so many donated cells? I can’t afford this habit otherwise.
6 Likes
Yeah I generally avoid the dead center for sure, but for these bottom vent cells I tried to stay inside the center ring lol
2 Likes
@Arch I was made aware that you might be using cells with bottom vents, can you let us know if you’ve faced these issues as well?
Follow up: I built the pack. I covered the inner circle with the fishpaper dots and welded on the outer edge after trimming the cell wraps a bit. The nickel covers the vent about halfway. It would have been a pain to cut a perfect hole in the nickel for the vents tho. Hope this is safe enough. It won’t be used very hard anyway.
3 Likes
aren’t you essentially sealing the vents with that method, effectively negating their benefit/intent?
kinda, yes. But I had no other easy option. The top vents should burst before the bottom vents anyway.
Halfway sealing them is probably better than completely sealing them.
Also, these were cheap cells used for a low power ebike. Otherwise I wouldn’t have bought them.
I’m just really glad I don’t have to deal with these vents on the Lishen LR2170LA cells I just opened up today.
1 Like
