Cordless drill PWM speed controllers interchangeable?

[John Doe]

Wondering whether I can hook up one cordless drill power circuit to
another cordless drill motor of equal or greater voltage.

I hooked up a 14.4 V cordless drill battery and PWM circuit
(trigger) to a 36 V cordless drill motor and it seemed to work fine,
probably at a lower maximum speed. Is that the only rule, make sure
the power circuit voltage of the controller is no more than the
original power circuit voltage for the motor?

I suppose current is another concern, that might work against the
lesser voltage PWM circuit. Maybe just make sure it doesn't get hot?

Thanks.