I am just running the stock battery. I always try to get my RPMs up and pull so that I have the most output. Got myself out of a deep steep ravine pretty easy and the stock electrical system didn't seem to have any issues at all. I was pretty impressed.
I also have the same 4K Terra series on my Mule FXT and have used it to pull out our 7000lb tractor that was stuck in the mud. It had to work for that recovery but was able to do the job so I was very pleased with the winch. My buddy that was helping me get the tractor out went and bought a Terra series after that.....
Amazon had them listed for about $227 when I looked. The other nice feature is it has a LIFETIME warranty from a major player in the winching business.