Below you will find some links that will help you understand and use BaseBuildingPlus to its full advantage.
How to use the Solar Panel :
Place the Solar Panel in direct sunlight.
Attach the wire to a Truck battery, and attach that to the Solar Panel.
Attach a 4plug socket to the Solar Panel.
(This will be used to transfer power from the Solar Panel to a convenient location for you to attach other things)
With the 4plug socket attached walk to your desired connection hub & place the 4plug socket down.
Connect a Cable Reel to the 4plug socket and attach it to whatever electrical device of your choosing.
Turn on both the electrical device of your choosing and the Solar Panel.
Enjoy having power.
The truck battery seems to act as a catalyst to allow the Solar Panel to produce power while the sun is down.
The solar panel should (I haven't tested to confirm) charge the Truck Battery during the day.
You can turn off the Solar Panel to cut the power to all the electronics at once.
(Great for if you've got a lot of lighting attached to 1 solar panel)
I have 2 4plug sockets attached to my solar panel.
1 of the 4plug sockets is connected to my 3 spotlights for my watchtower.
the other 4plug socket is connected to my compound lights.
at night, I go to my Solar Panel and turn it on... turning on all 7 of my spotlights.
There are other ways to use the Solar Panel, this is just the best that I've found.