Problem is whith my iPhone 3g. Some time ago it began to show that the battery is should be charged. I have charged it, but still it is red (like less than 20 %) but it works normal. The problem here is that I don't know if the battery is really empty or nor, and if I should charge it or again not). So what should I do?
Have you tried a restore? Sometimes it helps with weird issues like that. My iPhone 4 had great battery life in the beginning, but after a couple months it started getting horrible. Did a restore and somehow it fixed the issue. Of course, my battery was showing the correct charge though. I would try a restore, then call Apple if it doesn't help.