[tchvil]

As pointed in the article, battery packs aren't that expensive.

When my last of 3 Makita battery pack died I found reasonably priced battery holders with a PCB: https://a.aliexpress.com/_EjvvWY7

10 high current LG 18650 cells per pack.

Plus a cheap but good enough spot welder($65 I can reuse), some nickel strips and I ended up at about the same cost as the original ones on material alone.

[monkmartinez]

No way it was close! I just did this on for a 6AH Makita. First of all, taking apart the pack... for science, the batteries were name brand but not the best and were under-rated capacity.

Second, I shopped around and found LG MH1 INR 18650 3200mAh HD 10A for under $5 per cell. So my 5S2P (18v 6AH+) battery with BMS and new case was less than $70 shipped with damn fine cells.

The cheapest knockoff amazon battery that works with Makita is about $50, but those are seriously sus in both cell type and BMS. Homedepot has the OG Makita 6ah at $200+.

The only thing you need contemplate for DIY is the quality of the BMS. Don't charge batteries when you are not paying some attention.