Damn you @taz, you know this is true.
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Got to love ordering 20 things from aliexpress and having everything show up but my roll of nickel 
. Its been over 45 days with no update. Looks like I’ll order some from ebay.
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Just built my first battery. 12s6p made from 40t cells. I soldered them by hand (not ideal I know). I slapped a d140 bms on it and now am praying to god It doesnt ignite on me.
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Got some pics?
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Pics or it didnt happen
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You soldered nickel to the cells!? Why didn’t you just use copper bro?
I only glanced at your pictures but my advice would be to not use that pack.
If I were you, I would take a step back, research a lot more and consider your options from there. That pack looks dangerous dude.
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it’s not the worst we’ve seen around here 
some positive points:
pgroups are wrapped in fishpaper
its got 42v and no smoke yet
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Yes it could be much worse nothing that isn’t fixable
What wiring diagram did you use ?
It might be 42v just sitting there, my concern would be how that pack deals with vibrations. And my guess would be probably not well.
Sharp edges of nickel sticking out from the pack are pretty concerning too.
The reason we use nickel is so we can weld it to the packs. If soldering, copper should have been used. Without roughing up first, solder doesn’t hold very well to nickel at all.
Edit: i’m not trying to be an arsehole here but even if this pack isn’t the worst we have seen, it’s far from suitable for it’s use case and needs work before it is safe
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So, I’ve been test riding my (mostly finished) ebike for a week or two now, and I am disappointed to say that my battery pack is by far the limiting factor 
I tried to save some money by going with cheaper, lower discharge cells (Nkon had NCR18650PFs for $2.00) since it was such a large pack (20s7p), but the voltage sag is unacceptable at the power levels I’m trying to achieve. I am now in the unenviable position of wanting a new pile of cells, and I figure this would be the thread to ask in, to see what the market looks like now that Nkon doesn’t ship to the US anymore.
Side note - Anyone interested in a ~1.4KWh 72v battery pack? I’ve got one, low cycles, probably good for 50-60A (Just not 120, like I wanted). It’s actually two packs - one 8s, one 12s, with a series link. I’ll find some pics later if anyone is interested. Full disclosure, it was soldered, not welded, but my technique is excellent, and very fast - low heat input.
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Check out this thread dude, a lot of discussion on US based battery suppliers.
Sorry to hear it didn’t work out!
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bummer about the pack. same thing happened to me in my first esk8 pack. The pack ended up getting paired with some hub motors and worked fine.
IMR has sales every now and again. very fast shipping, check out what’s on sale now. sure you can find them a little cheaper, but after all the time and effort of making a pack the difference seems negligible
30T’s 40t’s and 25s’s all on sale right now.
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This approach might be worth a look
It’s not that clear from his posts, but he’s using a high capacity low discharge pack in parallel with a low capacity high discharge pack.
The high discharge pack deals with peak demand, and the high capacity pack charges the high discharge pack when demand lifts.
To be somewhat safe, would need to choose the lipos very carefully and understand what the limits are.
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8s6p flat six block layout, no folded nickel.
In my experience though folding nickel between p groups is more likely to cause broken welds than broken nickel, but it also depends greatly on the direction of the folds. If the board nose is north, east-west folds with the bend hump deck side are the least likely to have issues if any at all. north-south bends and north-south nickel group jumpers are the biggest problems.
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I have a pack that’s divided into two sides of about 80mm (max) in width, so a total width of about 160mm. I want to put shrink wrap (lay flat) around each side individually. The pack has a height of about 18mm.
What size flat heat shrink wrap do I use?
Thought about using this but don’t know what size.
You want about 10% to 50% extra material…(160mm + 20mm) * 1.1 = ~200mm
Ah thanks! I meant both sides individually so calculated it myself, (80 + 20) * 1.1 (and 1.5) = 110-150 mm so I will try to find a size somewhere near those numbers.
First Battery Build - 12S 7P Samsung 30Q - Cells ordered from Liion Wholsale and delivered in 2 days.
I assembled the p-groups with neutral cure silicone and welded the nickel strips with a K-Weld. I used a mix of either 3 12 AWG wires or 2 10 AWG wires on the series connections because I didn’t have enough of either wire to do them all the same, but I doubt the electrons will care. I didn’t get a photo of the balance leads before I secured everything down but I made sure to run them individually and not cross any wires. I am using the LLT smart BMS for charge only and a charger port capable of handling 45A although I have it installed on a 6 amp charger. Shrink wrap will be here Friday, but I still need to peel back some of the Gorilla Tape to install the battery temperature sensors. I learned 90% of what I know about battery building here and on the old forum. Thanks to everyone here for sharing the knowledge
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