Pretty sure the 3rd picture doesn't work - I am no electrician , but the black wire on the right hand side doesn't seem to do anything ?
I'm no electrician but it looks ok to me.
Pic 2 shows 4 12v batteries in parallel.
Pic 3 first creates 2 24v batteries by hooking two pairs together in series (black wires). It then connects those two in parallel in the same style as pic 3
Could be wrong.
Please ask my wife to let me have a welding set

You also need to consider that it takes over 100 hours use to pay for the cost of the bulb. Fine if it's going somewhere like a lounge where it on for hours at a time, but the light in my loft gets used for a few minutes every few months. It'd take about a hundred years to save enough to pay for the bulb.You have to include the longevity of the bulb in any such calculation.
Could you get pedantic over positions.