I suspect the load might be less than you think because there is probably some gearing in the hoist mechanism so that a smaller motor can run it. As others have said, take a look at the motor and see what it is rated at. It will either be rated in watts (divide by 12 to get amps) or horsepower. One horsepower is 743 watts.
For reference, my sailboat has electric winches that will pull over 2,000 lbs. They don't cause a problem running off my 420 amp-hour battery bank.