Disassembled and made safe, pre-balancing and float charging

So after seeing @evoheyax 's beautiful board go out in flames, I realize I had no idea what I was doing when I made my first battery. I was basically on a month long drinking binge and just do not trust whatever has been done. I have to make this battery safe. Here is the issues that I have with the current 12s4p 30Q build:


  1. Did not use fishpaper. The only fishpaper was small pieces under the balance leads.

  2. No insulated caps on positive ends

  3. I only used one layer of 12mm .15 mm nickel strips. The seller says they are rated at 40 amps but from the tables I have seen recently, it seems way to high. Even then one layer wouldnt be enough for this 4p setup.


  1. Possibly most importantly, I dont trust the way I bridged my serial connections across the pack. I looked for several methods but I ended up just welding strips across then folding the pack outward to be flat like in the picture below. The first time I did this the stress of bending caused most of them to break off.


My ideas and questions.

  1. At this point I would love to try to pull off the stripping and reuse the cells since they are new. Of course they would have little metal burs that would need to be smoothed out. I have gotten mixed responses on doing this. In the video below the guy uses a dremel. Is this safe, or am I stuck buying new cells?
  1. What is the best way to bridge series across the pack? The way I did in this pic just seems like an issue waiting to happen. I like the way cell level fusing makes the connections across the top of the bus bars. Would it be stupid to make a nickel connection from each cell to a bus bar and then connect across the pack that way? If thats a bad idea, what is the absolute best way to make these connections?


Any other advise or help is appreciated.


Does you pack need to bend ?

No it does not.

Do you have a diagram of how your cells are layed out in your pack ?..ok nevermind,… i see how your pack is built in 1st pic

It’s just like this except 12s4p



My first pack was built the same way20170530_134130-2016x1512 but I soldered a 12G solid wire on Edge of nickel strip (Before) spot welding on cells…I also did put 1 bending joint in middle of pack just to be sure


Next pack will be made with these PCB glued on top of each parrallel pack.70A3CB60-5486-4D21-A295-80A515549CCB


So you will essentially use that like a double bus bar to bridge the connections. I like it. Where can I find those?

Think he made them

From PCBway.com,… someone i know ordered them for me .

in terms of salvaging your cells, no problem grinding the terminals to smooth out the burrs from prying off nickel. it’s just you can’t do it more than…once or twice since you’ll be removing material from the terminals which are already thin.

Thank you. Any advice on the best way to bridge series across the pack? I just feel like bending nickel like in the above pics is reasonable or stable. Is this busbar idea reasonable? If so do you know a decent source for the small brass strips?

Got mine from some huge 8 Guage scrap of wire that had about 8 strand of these solid wires in it…otherwise you can just spot weld 2-3 more nickel strips on top to increase amp capacity.

i’ll take some photos tonight, i’ve got a pack in progress now. my series connections are using flat copper strand.

i ran a 12s3p in exactly the same way you’ve constructed your pack and by the time i salvaged it, there wasn’t a single visible problem with it.

that’s to say, i don’t think there’s any obvious shortcomings with what you’re doing but in the spirit of safety, at least insulate your cells better. cap insulators, fish paper…hell, dime roll wraps.

Thanks you. I greatly appreciate this. I look forward to seeing the pictures.

Also try to make nice solid spot welds to prevent issues20160423_144858

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yea, those are nice beefy welds, evenly distributed. good point.

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In the meantime you guys have any good local US sources for adhesive backed fishpaper? I’ve found it in amazon but not adhesive backed

Well good on you for taking the hard decision to rebuild the pack. I think the cells will be fine to reuse if your not too rough with disassembly.

The thing that always freaked me out about some peoples packs is how close the nickel is to the - can where it welds to the positive terminal.

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here’s P group, fish paper both ends, then clear pvc shrink:


all cells have insulator caps, cut away pvc shrink, welded with tabs for series connection:


using copper strand for series connections, going to solder tabs to copper strand.


when pack is complete, each 6s6p group will be shrink wrapped again and slots cut through to allow for some amount of flex: