1D10T proofing a spring clip/clamp connection to a battery can be challenging. This is one way to ensure stuff is not connected plus to minus and minus to plus.
This is "method 1" for low current applications. There's another way for higher currents I need to make a video on.
WARNING: Electricity always comes with the risk of shock, fire, electrocution, etc. If you do not know what you are doing, learn first or don't do it.