The two lamps are to run in simulation. Notice positive battery terminals are connected to plate and negative terminal connects to welding rod. You still use welding helmet for arc welding.
Top welder with two batteries is for up to 22 guage material and lower welder with three batteries for up to 10 guage material.
Keep batteries at least 4 foot from work and for lead acid batteries weld with battery caps removed.
Of course, good battery connections are needed.
