Why am I blowing a laptop powerpack with dc water pump?

[hyphagon]

TL;DR Summary

Using a laptop power pack to a dc water pump. Starts fine then after couple of minutes starts pulsing. why?

Hi,

I have a water pump rated 12v dc 2.3A. I tried using Microsoft Surface powerpack rated at 15v dc 2.5A to power it. Pump just started pulsing. I removed the water pump and checked the voltage coming out the powerpack and it was fluctuating between 0 and 15v. Thought I had a dud powerpack so switched it for an Asus laptop powerpack rated 19v dc 2.38A. Checked the voltage before hooking up pump and steady 19v. Hooked pump up and it ran fine for 5 mins then started pulsing. Checked voltage and sure enough fluctuating.

I realise I am running over the rated voltage for the pump but I thought it would damage the pump before the powerpack as the rated power for the pump is less then that of the powerpack. This though assumes constant resistance and Ohm's law through the motor: So current pull drops as voltage increased. I guessing I was wrong and it also current increased which went over the rating of the powerpack blowing it?? Or is there something else at play?

Cheers Dan

 

[Baluncore]

If you are overloading the pump, it will require more current than specified. The power supply will then get hot and go into thermal protection mode by cyclically shutting down.

What sort of pump are you using, is it a piston or a centrifugal pump ?
What fluid are you pumping, what is the lift height ?

 

[Rive]

It would worth to check the actual current consumption of the pump. I have a hunch that it'll be something low, far from the rating.

Also: it's always better to use some 'dumb' power supply instead a repurposed smart charger.

Smart ones often wanna' talk with the equipment-in-charge, or has various economic modes of operation or so around batteries. A dumb one just does its job or stops if something is out of spec. Lot less problem.