In a cave we are exploring we are currently blocked by a small siphon, which we would like to empty into another gallery.
For this, I would like to use a 12 V pump (not selected yet). As a power source, we would like to use the 36 V Li-ion batteries from our big hammer-drill.
I see 2 options:
- Using a DC-DC converter to convert the about 36 V to 12 V
- Using a MOSFET (+ free-wheel diode) to apply PWM, with a duty cycle of about 33% (to be adapted based on measured battery voltage)
For option 1, is there any precaution to be taken because the load is inductive rather than resistive?
For option 2: is it OK to apply such a high voltage on a 12 V motor if the average voltage remains within specs? Is it OK if the motor is a brushless DC instead of a brushed one (I think not, but not sure)?
Is there a significant difference in efficiency between both methods?