My iphone 5 is brand new and takes forever to charge. Why?

I just received the phone in the mail two days ago and for the first charge I took it out of the box, plugged it in and it was completely dead. Took over an hour to start up, and after 12 hours of charging wasn't even at a full charge. Should I try and get it repaired?

Do a firmware reinstall. Put it in recovery mode and connect it to iTunes. I tunes will ask if you want to install the latest firmware. Select yes. It will download and install it. That should fix the problem.

May I ask where you bought it from?