My battery making progress (Mostly photos - to keep them in one place)

first spotwelds ( with a homemade welder which i dont know the specs of and 0.15mm * 8mm nickel)

First few Series conections (15avg wire x4)

Starting to come together

XT90 termination (made sure to not have air bubbles in the middle) - whole lotta flux and solder

Pictures showing the outside of the pack, mostly S connections. Brown stuff is flux - should have wiped that down
I have a shit phone - sorry about the glare

Finally, the finished pack, i let my OCD take control with the balance cables haha

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Spotwelds dont look as promising as they hold, but they do their job. - Passed the pull test

I ran out of black and red wire so i had to use this blue and green one, same thickness, altho less copper strings.

At the end of the pack the 5th wire is for the bms.

Everything is double insulated( kapton and fishpaper)
There is two layers of fishpaper in the middle of the pack.

12S4P P42A

Should be good for about 100A safely.


Good deal, a little unconventional with the series wires on the sides of the pack but it shouldn’t be bad as long as it’s not subject to abrasion. If you haven’t seen the duck battery tabs take a look, they are cheap and really high quality. I’ve used them on a few 18650 and 21700 packs and need to find a use for my other nickel strip as I won’t go back to trimming and sanding my own stuff.

Keep an eye on the outsides of the pack where it is only kapton tape as it’s not very abrasion resistant and slap a piece of fish paper on any wear you see.

Balance leads look neat, good job. Take that temperature probe and silicone or tape it to the pack somewhere, i don’t know where it would be best but i put mine on one of the series connections in the middle but because your cells are split maybe there is no advantage to that?

After you get that baby charged and balanced (i set my delta at 25mv) take it for a little run and check on it periodically and open up the enclosure after and look for wear. If you do find anything post an update, i eat that shit up. :call_me_hand:

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Sometimes flux just doesn’t want to clean off. You can try and use a cotton swap and isopropyl alcohol but then after it dries it is still there somehow? When that happens i usually have more luck gently scrapping it off with a finger, or you could use a plastic tool if you don’t have long enough nails.

Pro tip for zip ties: buy an angled plastic cutting tool. Something similar to these works super well for getting the ends to cut flush with the box clicky box part

Those are more expensive than most of them are but it was the first google result that had a version with a spring/tension in place and that was a good size. You want a type with a thick cutting blade as the thin ones won’t be able to snip through zip ties in one cut.

example of what I mean by thin ones:

The balance wires look really good :ok_hand:


I have been getting better results cleaning the flux up hot, i keep a paper towel handy when soldering and wipe the joint down as soon as the solder solidifies. It gets all the big stuff and if im feeling really ambitious a little 99% iso on a microfiber rag to get the residue but unless im going to apply conformal coat i dont care enough to mess with it after the hot wipe

I’ve found that my flux can sometimes feel sticky so I try and remove it, but also I just hate the way it looks even if I’ll rarely ever see it :rofl:

That and I do tend to put conformal coating for extra protection where it is feasible to add it

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Gahhhh! All this talking about conformal coating and i just realized I forgot to do coat my solder joints before i wrapped up my current pack build :frowning: man the shrink turned out so good on this one too

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I’d say leave it be because it takes forever to get the heat shrink wrap to de wrinkle. :weary: To the point where most of the photos I’ve seen on here aren’t even fully shrunk

Also if you wrap it and then cover the ends with liquid electrical tape, or a silicone, then that alone should be pretty water tight. I don’t use conformal coating on my batteries since I have to use it outside and I don’t like the idea of leaving a battery outside for several hours. The stuff I have dries fairly quickly but it takes a while for the smell to die down.

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