I can verify that this will work. Using two car batteries I field repaired a bracket for a hydraulic water drilling rig in Honduras. I have a few comments on the linked video to make it easier for SurvivalBlog readers. First, use an old wire coat hanger for your welding rod. Second, Mark in the video appeared to swap the polarity of the electrode before and after. Positive DC to the stick (electrode) puts more heat into the workpiece, negative DC to the electrode puts more heat into the stick (for thinner workpieces). Lastly be sure to use a second jumper cable between the batteries so you can get the highest power at the workpiece. This is also something you will want to practice on a Saturday afternoon in your garage before you need it, and don’t forget to toss an inexpensive pair of welding goggles in your toolbox!
DD in CO