A rough rule of thumb. A
windlass draws nearly as much power as the engine starter. In fact the motors are rather similar. If your battery would be run down by cranking the starter for several minutes straight, then don't be surprised if the
anchor windlass runs it down also.
This is also why on most boats with separate starting and house batteries, the
windlass is wired to the starting battery. Best strategy is to start the engine before hauling the
anchor.