pic: Testbench with PDB backpower

[GeeTwo]

Originally Posted by bobbysq

I wasn't afraid of breaking it because previous experience has taught me that all of the 12v and ground rails were connected directly to each other.

They cannot all be connected directly to each other: each circuit has its own breaker and current meter. Running power backwards through the breaker would be of no consequence (as your power supply is probably not capable of enough current for long enough to trip a 40A breaker), but running current backwards through a current meter designed for polarized current certainly could.

I recommend verifying that you check on circuit you used as the "input", both to verify that it still works, and whether its current meter still functions properly before you build a robot with that PDP and have incredible fun troubleshooting the problem.

(Besides, you wouldn't have needed any more hardware than you have in the picture - just loosen the input 6AWG feeds into the PDP a bit, slide in your smaller supply wires underneath, and tighten.)