Hi Moggie 939;
Your Samsung should have an application call "Easy Settings". Mine is installed as a short cut on the desktop.
When you run this application it allows you to set the "Battery Life Extender" to on/off. When you set it to on, it will charge to 80%, if set to off - it will start charging to 100%.
Please report back if you're still stuck....
Also have a read of this thread:
http://forum.notebookreview.com/threads/samsung-series-7-weird-battery-issue.695611/
Good luck.