Arc welding structural steel with lead-acid batteries is well-established among hobbyists. Here's somebody who reinforced their truck bumper using six 6-volt go

Arc welding structural steel with lead-acid batteries is well-established among hobbyists. Here's somebody who reinforced their truck bumper using six 6-volt golf cart batteries, jumper cables, and filler rod, in 2008: https://www.instructables.com/Golfcart--Welder/ https://www.instructables.com/Golfcart--Welder/