I added a boat battery box under the driver's seat and put in the biggest car starting battery that would fit. I believe it is a 750 cca sealed battery. Anchored the box to the frame and filled the sides with closed cell spray foam to seal out water, mud, dirt, etc.
Be sure to use a proper size wire ga. for the length of cable needed.
I did this in 2018 and no problems yet winter plowing snow or summer. I use it yr. around.
Old School