This is an ammo case from super cheap for $20
and they fit 3 DIY 12V Complete Battery Box or Storage Case | 3S 12V 18650 Lithium with BMS 18650 Lithium with BMS They hold 21 18650 batteries , and I used my homebuilt spot welder, but you can buy a spot welder for $50-60 from Aliexpress or Temu . you can add USB port carlighter ports , swiths toy turn it on and off posts for charging . there is enough videos on YT about builds
Where to get 18650 batteries ? Well I could buy from old drill batteries from scrapmetal yards but due to fires , you have to source them for other places. FB market has been a utter gold mine for me you will have strip dill batteries or old laptop batteries for the cells toss out damage cell , like the one below DO RESEARCH ON THEM , YOYU NEED TO DROWN THEM IF A FIRE START , THEY WONT GO OUT LIKE A WOOD FIRE .
THEY ARE DANGEROUS
This is Adam Savage did a video on the batteries
The Surprising Flaws in 18650 Lithium-Ion Batteries
