Welcome fell.
I think what we are saying in laymans terms is that if you were using this tool with a battery alone, it would need to be a 12ah one, or about 1/3 the size of an average car battery.
The actual current pulled by the winch motor will be more, much more, this is justy a educated guess, but spose the winch is 500kg and its moves fairly slow the motor would be in the region of 350 to 500 watts, which is about 30 to 50 amps, and if you were to stall the motor maybe 4x that.
I suggest you call the manufacts and ask them how much current is uses.
One way to solve your problem cheaply, and if you were not using the winch for long periods is to have a battery connected to a charger to supply it.