brought this with me on a trip to AZ where I knew I would be using my GPS on my phone more than usual. as I thought, I found my battery was about 30 percent by about 3 in the afternoon. Pulled out my new battery pack and stuck it to my phone. The magnet worked great, but the battery pack got extremely hot. Hot to the point it was un comfortable to hold, also my phone battery never increased simply maintained the 30 percent I am sure due to the continued use. came in handy but probably would still prefer a cord.