Li-ion battery – assembly process

Spot welding yourself?

Spot welding of batteries for an electric bike is quite an ardous task. However, it pays back to do it on your own, because on this element we can save the most money. For example, the battery, which spot welding I will present, cost me around PLN 450 (~$115). Its capacity is about 570Wh (48V 13S6P, 12Ah), which is enough to cover about 50-70km by bike with an 18A controller (max 850W).

How to do it

and what will we need?

I will show you the whole process in the video below. Also, I will show there the tools I used. You will need a spot welder, and you can read about my spot welder in the PREVIOUS POST There is also a schematic diagram of its electronics there. The cells I used come from dismantling a larger package, but they have nominal parameters – they are like new. The whole idea of welding is the same for all cells, and the ones I used were SONY 18650V3 2150mAh and I was able to buy them for PLN 4 / pcs (~$1). I used about 4 meter nickel tape at a price of 5.5 PLN (~$1.3) per one meter.

(Polish version)

Photo Gallery

bms soldering

(Polish version)


  • SONY 18650V3 2150mAh cells (unpacked) 78 * 4 PLN (~1$) = 312 PLN (~$78)

  • nickel steel tape 8×0.15 4mb * 5.5 PLN (~$1,3) = 22 PLN (~$5.5)

  • triple holders 52 * 0.7 PLN (~$0,175) = PLN 36.4 (~$9)

  • BMS 13S 20A PLN 66 (~$16.5)

  • connectors and cables PLN 10 (~$2.5)

    Total PLN 446.4 (~$111)

Stay tuned:

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