IPhone5 read 5%, plugged in to charge then instantly read 26%?

It's been doing this a lot lately. Earlier it read 37% and I restarted it and it read 63%. Do I have a bad battery or is the percentage reader just not accurate?

I personally don't own an iphone5, but I think I know what you are talking about. Same thing happens with my ipod touch 2G. It doesn't show the exact percentage, but the green light (showing it is done charging) will turn on a bit early. I think it may be a glitch. The best thing to do is return the charger and try a new one. Most store policies have a 30 day trade in policy. If not, it is best to just keep track of the time you started charging your iphone, so you know when to unplug it.