I just do what I’m told Mario. Don’t hurt me.
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I’m sorry Al…
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That capacitor is nowhere near enough. You’d probably need like 600 of those to even have a chance at welding. If you want to use capacitors, look at this: kCap ultracapacitor module | keenlab
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I use 3 of the LiFePO4 280AH cells on the KWeld. Gets right at 1800A. 4 would give overcurrent faults.
The price of those have gone up significantly so that size isn’t really worth it anymore. I use those as the main battery in a camper so it was easy to move it into the shop and use on the KWeld.
If I were to get a dedicated KWeld battery pack, I’d look at this, which is a really reasonable price and shipped from the US. I think a good ~100ah car battery is going to run $150-200 anyway, and this would provide a lot more current, and a much more consistent voltage.
Or about $30 cheaper shipped on AliExpress
So I’m trying to build a 12s3p battery pack to go in an old kaly enclosure. Initially I was having some other guy do it who built my last longboard pack because I couldn’t be bothered to get a spot welder. Problem is this guy built it in some ass-backwards way that I didn’t want and then decided not to finish, so now I’m trying to finish up. Luckily, he at least got the spot welding “done” so I’m now trying to solder the series connections onto the P-groups.
Problem is, when I was soldering the wires onto the nickel strips, some flux leaked down under in insulation rings on the positive terminal. I don’t know if it shorted all all, but I think I heard some bubbling.
The flux says it doesn’t need to be cleaned, but I’m new to using flux and far from an expert. It’s this stuff:
How big of a problem (if any) am I looking at going forward? Is this likely to cause a short in the future?
*Also I’m going to fix up those solder joints 
Flux generally bubbles when it’s heated by an iron, and far as I know, it’s not as catastrophically corrosive when it’s cold. However, the cell cans are steel I believe, so they’re more at risk of corrosion than the nickel is.
Flux, however isn’t itself conductive.
The looks of that pack though, is a bit concerning. Series connections being soldered right onto the cell cans isn’t a great idea. The heat transfer is significant, especially at the negative end.
I realize you’re trying to finish a project that was already started, and chances are it’ll end up functional, but it looks like you need to proceed very very cautiously, and then dial down your expectations of the performance and lifespan of this particular pack.
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Awesome thanks!
Lol and the sketchiness doesn’t end there! This is definitely not the way that I would have done it if I was going to build it myself. I’ve been trying to be very careful with the heat so far, so hopefully it won’t do too much damage. And I’ll probably pull very modest current numbers from it.
Trust issues established 
. I’ll probably buy a spot welder and do it myself next time I need a battery pack. I’ve seen enough tutorials to do a way better job than the guy that did this. Might even teardown the one for my longboard to see what surprises are hiding under the shrinkwrap 
Still not super happy with it, but at least it’s mostly done (except for the balance cables that I haven’t sorted out yet.)
Tried to keep heat on the terminals to an absolute minimum, so some of the solder joints might not be perfect still, but at least nothing was super hot to the touch after soldering
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No chance of a short. Some possible corrosion long-term but rosin flux is pretty mild. Same for minor leakage current, it’s a possibility but rosin flux isn’t very conductive.
If you’re worried about it you can flush that area with some isopropyl (rubbing) alcohol to dissolve and wash away the flux. It should dissolve easily.
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This is a smart but potentially painful exercise. Godspeed.
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Hey all is there a way to rename your LLT bms in the app to avoid confusion w multiple boards? I feel like there is but I can’t figure it out 
Android phone if that helps.
Yeah it’s kinda obscure in the menus, it’s in the “App Settings” tab, top entry.
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Thank you 
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I was thinking of using some isopropyl alcohol on it, but I feel like that might just make more of a mess than it’s worth at this stage. I’ll probably leave it for now if it’s not a big issue. Thanks for the suggestion
Emotionally and physically haha. Thanks
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Hey guys
Do any of you know what to do with the switch on this LLT Power 12S smart BMS?
There is a red and a black wire that comes out the switch port on the BMS and there is around 12V across it. I assumed if you close the switch (shorting the wires together) it might turn on/off the current limited BMS output but it doesn’t seem to have any effect. When I closed the switch there is around 1mA of current draw which makes sense, people commonly use 10k pull up resistors for digital logic.
I’m only using the BMS for charging, not discharging, so should I just leave this switch open?
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Yeah dude just leave it open! Still does everything it needs to on the charging/balancing side of things
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Thanks dude 
can some experts help to confirm this
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