I would add motor home engine
Generator
or you mentioned working on the water heater.
Generally if you start it and run it for just a short time batteries die
Takes a fairly decent amount of time.. For starting batteries and an easy start perhaps 10 miles but for house batteries six hours of run time on the Genny
It is a numbers game. Starting for example draws 100-200 amps for 30 seconds (one hopes) or less that's around 1-2 amp hours and a 100 amp alternator can swiftly replace the charge. but repeated short runs will still deplete the charge.
House batteris often give up 100, 200 300 or more amp hours before they can not start the generator. TRakes 6-8 hours to fill 'em up with the proper size converter.. LONGER if the converter is smaller. .(mine is)
Home was where I park it. but alas the.
2005 Damon Intruder 377 Alas declared a total loss
after a semi "nicked" it. Still have the radios
Kenwood TS-2000, ICOM ID-5100, ID-51A+2, ID-880 REF030C most times