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10A device to 5A supply?!

Discussion in 'General Electronics Discussion' started by Nael, May 24, 2018.

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  1. Nael


    Oct 12, 2016

    I'm buying an Air Inflator for my Bike, it says 10A maximum on it which meant to be connected to car cig adapter, but I'm using that at home, and only way to supply power by my bench power supply which has a maximum of 5A output, what will be the consequences ?

  2. 73's de Edd

    73's de Edd

    Aug 21, 2015
    Sounds like you will be getting pump action, when starting at a low tire pressure, but as the current demands start increasing, in getting on up towards that 70 ? lbs. Then the unit will slow down and stall out on you.
    With you never being able to achieve higher tire pressures.
    Try it and find out . . . but shut down before any overheating.
  3. dave9


    Mar 5, 2017
    It depends on what your bench power supply does when the current is exceeded. If the bench supply shuts off then the pump will stop. If the bench supply drops voltage the pump will slow down.

    It is probable that the peak current is starting the pump motor so it may not start at all or start slower depending on the conditions above. You might be able to charge up a high farad capacitor array to supply the peak initial motor start current, get the PSU past that hump till it can supply nearer the needed current.

    Personally I would just buy an AC mains powered pump instead, or get a 12VDC supply capable of more current, for example a cheap generic ATX PSU, the kind of cheap low quality product that you'd never want powering a PC, should do fine with intermittent duty powering an air pump, but since it is a cheap low quality unit, you'll probably need to put a dummy load on the 5V rail to keep the 12V rail at a high enough voltage.

    Also consider that a good design for a 12V pump would allow it to also work at the higher voltages a vehicle electrical system can generate, so you would have better pump performance shooting for say 13.8V instead of 12.0V, and if the peak is 10A at 12V, it would be higher at 13.8V.

    If you just want to use the bench supply and it's shutting off, put a low ohm resistor in series with the pump. It'll run slower but it will run.
    Last edited: May 24, 2018
    Nael likes this.
  4. Nael


    Oct 12, 2016
    Thank awesome info ;)
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