I have had a Sullivan starter powered with a small lead/aid motorcycle battery for over 30 years. I always use an inline auto fuse on one wire, because my flight box is made out of sheet steel. I cannot recall the details of 30 years ago, but I imagine I started with a 10 AMP fuse and increased it as needed so it would not blow. My guess is I am using a 20 AMP fuse. I don't recall ever blowing a fuse after the initial testing.