My iPhone battery is decreasing, yet it says it is charging
I have my iPhone plugged into charge, and it has the usual notifications to say it's charging however it keeps losing charge rather than gaining it. I recently had a problem with a loose battery - this was fixed in store and the diagnostics still said my battery was fine, so I don't think it can be that. I have used two different cables to try and charge it, one is pretty much brand new and both a verified apple cables.
Has anyone else experienced this?
iPhone 5, iOS 8.2