The no controller with the 15w ASSumes the batts will start the day down some and take all day to get to the 14s. With storage you have full batts starting out that day, and the controller's high set-point keeps the batts from going too high and losing "water"
Even though this solar is not intended for camping, it remains that you can get more "real" solar for the same money. It (say an 80w panel) would be no more awkward for the storage scenario, plus it would be useful if dry-camping plans ever changed. and could be expanded (another 80 and hinge them and you have a 160 suitcase eg)
With that in mind the controller should be more than needed at first. Might cost $20 instead of $15 on eBay. :)
