Yes, Geri B they will ignite. My grandson saw my pile of dead 9v batteries sitting on the counter waiting to go to the recycler and stuck them together matching terminals. He then proudly told me that he had recharged my batteries for me. When I questioned him, I went to the batteries and they were so hot I had to use oven mitts to pull them apart. It only took about 2-5 minutes for them to get that hot. Thank heavens grandson is 10 and wanted to brag.