OS X Yosemite - Battery Percentage 'Stuck'

I recently updated my laptop (Macbook Pro 15" Early 2011) to OS X Yosemite from OS X Lion and have found that the battery percentage up in the top menu bar no longer displays the right information. It's almost as though it isn't updating at all to what the battery level should be. The only time that it 'updates' is when I turn the 'Show Percentage' option off and on - then the icon and the battery percentage changes to what it should be at. However, it then sticks at that until I turn 'Show Percentage' off and on again. It happens when charging too going the other way, I could have it on charge for hours from 8% or so and it'll stick at that number despite being fully charged until I 'update' it as per the above. I could even unplug the charger and it still displays the 'charging' icon rather than switching to the battery icon (despite the battery depleting as normal).

Also, whenever I charge it to 'full', it only ever gets to 98% now and says that the 'Battery is Charged'. I've attached a screenshot to show.

Any help would be much appreciated!