A standard battery charger wouldn’t even put a dent in that.
If he had a forklift battery charger on 220 it might have worked.
The usage was high but short duration.
I just doubt he ever charged them after assembly.
Yes he was trying to be funny with the eel thing by tossing them in the pond, then he showed them recovered from the pond, shaking his head. The core deposit on 100 batteries has got to be worth it.
the battery bank build looked quite tidy, wiring seemed quite well done
using a log splitter as a contactor/relay is clever, with the spring force holding the plates together.