How do I calculate voltage on a multi-powered DC circuit where all ends go to ground?
A side-note: voltage does not flow. Voltage is the difference in potentials. Current is what flows.

According to Kichhoff's voltage law, all circuits connected in parallel must have the same voltage across them. That means, if you connect two voltage sources, their voltages WILL get to be the same. If originally they have different voltages, then enough current will start flowing so that the voltage drop across the wire &amp; internal resistances of the power sources will make up for this difference, and that may easily destroy one or both of the power sources. Having a diode in series would let you solve this issue without the destruction of the power sources...