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Run this 1.5v pump from a 18650 battery

Discussion in 'Power Electronics' started by Nicholas bray, Dec 19, 2015.

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  1. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Hi I'm new to the forum

    I was wondering would I be able to run this pump designed for 2 x aa batteries connected in parallel from a single 18650 battery which obviously has a higher voltage of over 4v fully charged reducing to 3.6 as the battery reduces in power
     
  2. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Screenshot_2015-12-19-21-47-15.png
     
  3. Bluejets

    Bluejets

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    Oct 5, 2014
    3 x !n5401 diodes (3 amp 100v) in series with the motor.
     
  4. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    So its as simple as 0.7 voltage drop x 3 = 2.1v
    3.6-2.1=1.5v ?
     
  5. Alec_t

    Alec_t

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    Jul 7, 2015
    Are you aware that for safety reasons the 18650 battery needs protection from over-discharge?
     
  6. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    I'm new to using 18650 batteries but I did read recently that running the battery until completely discharged can leave the than battery useless and you won't be able to recharge it is that what you mean ?
     
  7. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    I have only used the batteries in my headlamp until now and haven't let it completely run out my kids have bought me a nitecore charger for Christmas as I don't trust the cheap charger that came with it
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Many cells are "protected" which means they have a cutout if the voltage goes too high or too low.

    The limits are such that the cell should not explode, but the cell can still be damaged.

    The easiest way to see if you have a protected cell is to measure it. The "protection" is a small PCB on the end of the battery inside the shrink wrapped cover.

    An 18650 battery should be 65mm in length. If it is a few mm longer then this is most probably the protection circuit.
     
  9. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    That's interesting to know I had some ultrafire batteries which came with the headlamp I know there are supposed to be alot of fakes around but I have to say once charged will run my high power torch for around 5 hours before the light dims a bit I'm curious to measure these to see how long they are
     
  10. Colin Mitchell

    Colin Mitchell

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    " bit I'm curious to measure these to see how long they are"
    They are 65mm
     
  11. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    So no protection circuit
     
  12. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Did you measure yours or did you take Colin's word for it?

    Colin's pronouncements are not always to be taken heed of.

    I went and grabbed some 18650 cells which measure about 66mm in length.

    In addition to this, the cover of the cell has printed on it "Rechargeable battery with PCB", and "over charge and discharge protection" (amongst other things).

    Do your cells have similar claims on them?

    Regardless of the protection (or lack thereof) you should use a proper charger. There are many USB powered ones on eBay.
     
  13. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    No not yet I've been to bed
    lol
    I have bought a nitecore charger which I've read is a quality one
     
  14. GPG

    GPG

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    Sep 18, 2015
    PWM the motor, dropping the voltage is wasting power. How much current does the motor draw?
     
  15. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Sorry I don't know as I haven't bought it yet I'm trying to decide if ill be able to run it of a rechargeable 18650 before purchasing it
     
  16. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Screenshot_2015-12-22-22-01-57.png
     
  17. Nicholas bray

    Nicholas bray

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    Dec 19, 2015
    Would this circuit work ?
    I tried to simulate running it from a battery and it failed due to lack of a ground
    As soon as I run it from a vcc supply and included a ground it ran ok
     
  18. GPG

    GPG

    452
    66
    Sep 18, 2015
    Yes but it is wasting more power than the pump uses
    Simulators need a reference to crunch the numbers.
     
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