When I put my test bed together I bought a new battery for my riding mower so the 3 yr old one could spend the rest of its life indoors. It was maintained with a Mattel Power Wheels charger. Never tested a mechanical limiter though.
I never considered current for my test just correct voltage. Since I now know the limiter is mechanical, it makes sense current is a consideration.
Since I have a lawn service and no time to cut my own grass or own anything that has a 12 volt battery that's not automotive in size (lol) and my duster is nowhere near needing a battery of its own, I' re do the test out in the driveway using my sons jeep battery as a power source. Are 10, 25, and 75 ohm resistors close enough to mimic sending units near empty, half scale and full?