If +/- is idiomatic is an interesting question. But then, does it need to be? It's a matter of lining up the shapes on the device with the shapes on the batte

If +/- is idiomatic is an interesting question. But then, does it need to be? It's a matter of lining up the shapes on the device with the shapes on the battery. You don't need to know what the shapes mean, just what their relative position means.