Thanks for the help Amadox, this solved my problem!

Thanks for the help, but I was also wondering, how could I make it so that they completely unload at the controller? 

  I really do enjoy this game but for the past few days I have been stuck on this one problem. When I am trying to program my creeps that handle upgrading the controller, I continue to have the same problem which is that they will only pick up two energy (they have only one work part), and then deliver it to the controller. If any of you know a way to have the creep harvest a full load and then deliver the whole load to the controller, it would be greatly appreciated if you left a comment here.

-Thank You

PS: If you wish to have any further information on my problem feel free to ask for it.