So I have a simple system where I want to run eight large DC brushed motors (for wheels) in parallel, which should give them all the same voltage, and they should independently change rpm depending on the torque they face (from their torque/rpm curves). The circuit is just this power supply and these motors and some wire, nothing else (no controller beyond me fiddling with the main voltage):
But they're not showing the right voltage, and when facing different torques, they act VERY weird.
When I apply 5 volts (deliberately low so I don't cut my fingers off messing with the wheels), the motors all run the same speed when unloaded, but are each motor is only showing 3.2 V (as measured with a multimeter at the motor itself). If I raise or lower the voltage, there's always a lower reading at the motors. And the power supply voltage is correct (verified by multimeter) and in constant-voltage mode. Maybe back EMF, but this seems huge?
But this gets really weird if I grab a wheel to stall it. As expected, the current rises (still well within the limits of the supply), but all the other wheels spontaneously slow down too, and their voltage drops even further from the supply voltage (~2.5 V). Stalling two wheels further accentuates the problem.
So my questions are quite simply: why is this happening and how do I stop it? I could power each wheel independently, though I'd rather not given that there's eight of them.