Recently, our batteries failed. I replaced them with 12 volt batteries with 7.5 and 12mah. I saw how some blub put them in Harbor Freight ammo cans but did not like the wood support they used. I have 3D printed supports to keep the batteries relatively snug. I am printing them out of Blue PETG to prevent warping but you could use ABS if you take into account shrinkage. More to come.