# Is there voltage across the negative terminals of 2 batteries?

I understand that voltage is all about potential difference between two points, and that we can't really determine an "absolute voltage" of any point, only with respect to some arbitrarily chosen reference point, such as earth or infinity. So in batteries, for instance, it only matters what is the potential difference between the two terminals. So my question is, if I take any 2 batteries of same kind, can there be potential difference between their 2 negative terminals?

This question applies to any power source: say I have 2 USB cables connected to different power sources, could there be a voltage across the two negative wires of those USB cables?