using portable jump starter for launch power

I got my wife a portable jump starter for her birthday. It claims it can power

12 volt acessories for hours. I was thinkng about setting up a system like an old Estes Astron system that used jumper cables on one end. We were using twenty feet of speaker wire and car battery (not the one in the car) or the battery out of the cordless drill, but this would be lighter. The speaker wire was in my range box that was lost in my rocket room fire in July, so I am starting fresh with new ideas. I just rebuilt the workshop and it's cool.