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sorry about the post. Don't know what went wrong. It's a geared three-quarter HP electric motor that lifts 4000 lbs about 10'. It's an ACE Boat Lifts 401 power hoist
I'm too electrically dumb to figrue your efficiency calculation, but the single phase remark is very helpful Thanks.
Let's keep it public, John.
The energy conversion doesn't have all that much to do with electricity. It's primarily elementary physics. Raising a 4000 pound load by ten feet requires 40000 Foot-Pounds of energy. That's about 15 watt-hours. That's how much energy storage you need if you want to raise the boat solely from battery power. Unfortunately, that number requires that the energy transfer be 100% efficient, and that you can extract all of the available energy from the battery, neither of which are valid assumptions.
You say it's powered by a 3/4 HP motor. One Horsepower is 550 Foot-pounds per second, so the lift could take as little as 40000 / (0.75 * 550) = 96.97 seconds to raise the full 10 feet at 100% efficiency. In all likelihood, it's geared so that it takes somewhat longer than that.