Since the Update to 12.04 my battery won't charge - it says it's charged to 51% - when i disconnect the powercable thee is no energy supply at all.
How can i figure out if it's a hardware problem or the new ubuntuversion? And how can i fix it?
Try booting to a LiveCD or LiveUSB for the version you used to have installed. This way, you will be running on a completely independent instance of the operating system, so if the problem persists you know it is your hardware and not the software. You could also try a LiveCD for Ubuntu 12.04 to see if it is a configuration issue.