I'm late to review this because I wanted to try it out and make sure I'm using it correctly. Even with a fully charged battery - and even when using a cigarette lighter adapter instead of a battery - it sometimes works and other times it turns off for no apparent reason. It's not an automatic shutoff - it doesn't even reach 5psi of my desired inflation (39psi). I also think the psi sensor is off by a couple of digits. Doesn't match what my car PSI says. (I'm also not saying automotive PSI sensors are perfect, but that seems a long way off.) But the biggest problem is that sometimes it works and sometimes it doesn't, and I can't figure out why.