Charges via USB, provides more than enough power for what I need. The power setting goes to 4 and I set it to 1 for the .010" nickel tabs and 2 for my .015" nickels. Setting a higher value will melt too much metal. So it's good to know that it can work with thicker material if needed. It's also very easy to use, I've set it to automatically spot weld a second after detecting a connection. I really have no complaints and am amazed that it performs so well in such a small and handy form factor. I'll be back if anything goes wrong, but I've made about two dozen welds and everything is going well. The instructions are translated well enough to be understood and this is said to have short circuit protection. In general, I'm impressed!