18650 series connection - Best practice

Looking for best practice to weld series connectors on my 12S4P Samsung 30q. On paralelle i got double 0.2x7 and on series i have 8x of 0.2x7mm but the other half of the series i dont have a good plan for. Any pics or advice to give?

I would seriously advice against making welds on the area not directly over the battery terminal cover, especially on the positive terminal side!


I tested. Its not bruning through 3layers of 0.2mm strip at my settings so i should be safe if that is what you are worried about. I also have fish paper insulator ring there. Could it still be a problem? Its kinda to late now :smiley:

What I used on a 6P 10S pack - double nickel strips 10mm x .15mm - wire is silicon flexible 12 awg- solder dabs on middle cross strips are for BMS balance wire connections

basically spot weld first strip directly to batteries - then pre-solder dabs on top strip - then spot weld top strip to bottom strip.

The dual series connections and parallel nickel strips provide optimum current sharing and redundancy


And the solder doesn’t come off with time and wear? I was worried about them coming off with movement :X

A properly soldered connection adhering to IPC soldering standard will never come off. So no need to worry there.

What kind of layout is the battery pack going to be in? Flat pack, vertical pack, modular? Because this is going to limit the options you can use to connect them in series sensibly. I have linked my two different pack layout builds (although vertical pack is not yet finished), so maybe you can get/find some ideas or help you make up your mind.


Personally I don’t like getting solder anywhere near the cell terminals, but if you’re okay with that then you can for example attach 4 mm bullet connectors to the parallel packs and then make short custom wires with bullet connectors to connect them in series. Then you can disassemble the pack later if necessary easily.

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It’s going to be a flat pack. Will check your builds after work. Thanks for sharing.

I love the idea of fitting bullet connectors so I can easy take it apart again. Will def look more into this and how I can securely fit the bullets.