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Building an 18650 battery pack!

CharlesR-22

I'm searching for suggestions on how to construct a 12V battery using 18650 cells. I've so far built a battery utilising Headway and Sinopoly prismatic cells. But I've stayed away from 18650s because they seem to be so difficult to find for a good price and decent quality. But I still want to make one.

This post is to get advice on the best course of action. I can solder even though I don't have a spot welder, but I'm not sure if it would be a wise idea for these cells. One thing I'm curious about is how many cells a regular 12V battery should have in series. If we were to use three AAA batteries, I was thinking of something around 60Ah.

With LiFePO4 we do 4s batteries but apparently with the lithium 18650s we do 3s?

Any thoughts on methods to hook these together would be appreciated. If it helps, the modem batteries I'm looking at are here https://18650batteries.nz/product/samsung-32e-18650-3200mah-6-4a-battery/

The specs are here https://cdn.shopify.com/s/files/1/0...sung_32E_Specification_Sheet.pdf?v=1614810892

Thanks in advance!
-C

  • Hi,

    The simple (but still good) answer is to not do it (any website that suggests it is safe to do so, is likely wrong/misleading).

    Manufacturers can get away with it (sometimes) because they can use near-identical cells in the pack construction. For individuals that is difficult to do, because even if they are purchased at the same time, there's no such guarantee. Manufacturers also have access to battery test equipment to help understand the individual characteristics of each battery to ensure they are matched.

    Each cell has the risk that it's slightly different to the others, and eventually have a different state of charge compared to the other cells, and some cells will overcharge as a result. Another problem is that if any cell fails, then you'll still be charging it, and if it's not an open circuit then that energy has to go somewhere, it will just locally heat the battery pack in that area.

    Plus there are construction risks, shorts during assembly or in use, and so on.

    As you say, soldering is not recommended.

    11.1V and 14.8V battery packs are very common/readily available, they are used by radio control hobbyists, and it would be cheaper to buy those than to design a battery pack.

    Another option (if you don't wish to buy a pack and wish to use a single LiPo cell, or if you need a specific voltage) is to use a DC-DC converter to get the 12V.