Some awesome stuff there. I like the multi-tap battery to vary the fan speed. The "welder" using a shorted battery is also cool.
at one of my overseas roles we'd bring in local tradespeople from time to time
a community outreach sort of thing
we had a gate to our compound that needed a welding repair
job was contracted to some local welders
2 of them showed up pushing/pulling a wooden kart
top and sides came off and inside was an ancient, and huge
single cylinder engine and genset, and a bunch of old truck batteries
assuming the batteries were wired in series, them and the genset had enough oomph to burn a rod
engine had a giant cast iron flywheel that they wrapped a rope around
then both of them grabbed the rope and started running
a few times the engine kicked back and knocked both of them on the keister
was great fun to watch
after quite a while they got the thing running and one of them set up the welding cables
put on his sunglasses, and started to burn rods
mid afternoon they had to pack up and get out
next day they were back, same routine
except the other one was doing the welding
figure the guy from day prior wasn't able to see yet