Isolating p groups in pelican case

Hi! I am learning how to build battery packs right now by watching videos, reading books and this forum. I never built one.

I am planning a build of a 12s5p molicel p42a in a small Pelican 1150 case.

Here is the layout:

If the battery is in that type of case and will not flex, is it better to isolate p groups with kapton tape or other material to prevent shorts caused by vibrations? Or just hotgluing all cells is ok?

Here you can see a top view with pGroups highlighted in red. As you can see, space is limited:

Here is top and bottom view:

What do you think? Enough space? How would you isolate pGroups in that situation? Or would you only isolate between the orange line in the first image?

May be it is too complicated and I might go with a 12s6p in a pelican 1200. But I like the idea of a smaller case.


For top case block battery’s I like to use plastic cell spacers. They are super easy to work with and make your battery strong and safe.

You can get them on Aliexpress.

Only hotglue is not safe and capton is not optimal as well. Ideally you use fishpaper or plastic sell spacers.


This looks very nice! Do you still use glue to hold everything in place?

Yes hot glue to hold them to the spacers. Some prefer other more heat resistant adhesives but if its finished it will be held together with heat shrink anyway.

Thank you very much for your replies!! Have a nice day!


another thing you might want to consider when designing your layout Is to avoid those narrow sections in the nickel. With a 5p of p42a you can draw serious current that may heat up those thin connections. You should probably double or tripple the nickel at this location or use additional wires on top.

I tought of folding the nickel to solve this problem. Do you think it is enough? It is 50mm wide nickel.

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Yep, I second this. Kapton tape is not abrasion resistant.

How thick is it? And how many amps do you plan to pull from it?

A general rule of thumb for the current handling of nickel is 1mm² can handle 10A continuously. So if your nickel is 0.2mm thick, then 50x0.2=10mm² or 100A continuous current draw.

5p of P42A can safely supply 150A continuous, so your nickel is a little under-spec’d if you plan to run that many amps.

I do really like your folded over wide nickel idea. That’s good outside-the-box thinking. What I would do if I were you is solder some copper (either the inside of a 12AWG copper wire, or some flat ¼" copper braid) along the edge of the nickel before you weld it in place.

Like so:


If your battery is getting hot enough to melt your hot glue then you have a bigger issue

After 100 packs I made with pvc purpose hot glue I dont recall any having any issues regarding breaking off or it melting.

Sillicone is messy af and takes too long to cure, other adhesives Im not aware of

Just put fishpaper between every p group and you will be fine, basically where ever us voltage difference put insulation :smiley:


It also seems like you have one 4 cell and one 6 cell p group.


You are freaking right!! I have to rethink this part!

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Thanks a lot for reply! 0.2 is what I would use. Nice idea to solder copper! I do not think I would use that much power but I prefer to make things as sturdy as possible.

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You could also do something like this. But i think a continuous piece of nickel that is prepped with some copper soldered on is probably the best way to do it.


Thank you again for reply! I think also think it is a good idea to stay with stuff people tried at first so a soldered copper or something like this is a better way to do it I think. Is there fishpaper arounf each p group on that photo? How does it hold altogether?


Neutral-cure silicone

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So to my understanding it is batteries of a p group first held with little spots of hot glue. Then silicon to secure them for heat. Then fishpaper secured with heat resistant tape. Then silicon (and maybe some hot glue first to hold in place) to hold between the fish paper of each p group. Is it right?

Where are you getting your nickel? I ordered my first welder (Malectrics) and need to start sourcing the bits and pieces so im ready to assemble my pack once it arrives.

Also a question… I get the whole path of least resistance thing so realistically there should never be an ark but is there any concern with your folded over method if there is an airgap or is it again because of the path of least resistance (law?) a non-issue.

Yep, that’s pretty much spot on! For my brick-packs I assemble all my p-groups and let them cure so they are solid, then I silicone them all together and clamp the whole brick together with really big clamps while it cures into a solid block :grin:

I get my stuff in bulk from china :grin:

I sell pre-cut tabs and 30mm nickel by-the-meter on my website, if you dont want to buy a kg and want it to your door in a reasonable timeframe.

The voltage across the whole folded nickel piece is the same, so there is no potential for a spark. That’s my understanding anyway. Some builders choose to insulate between nickel folds, but I have never had any issue with how I do it.


Never thought of that - Thanks for the link!

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Hell yeah this is what I do too.

So are you using the copper for only that one terminal end? Looks like you’re doing 1 or 2 layers of .2mm nickel for all the other series connections in this pic no?

Just trying to figure out the math here–what’s the “50” in this equation referring to? You would need 50 layers of .2mm thick nickel as serial connections to support 100A draw?