PMP - not accurately measuring voltage

Discussion in 'Power Magic Pro' started by Fruitflan, Sep 14, 2015.

  1. Fruitflan

    Fruitflan New Member

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    I have a new 3 month old battery and my PMP was working fine set to 12v for the first month of its use. After a month, it kept cutting out as if the voltage dropped under 12v. I tested several times with a multimeter and it was consistently over 12.3v while ignition was off and car parked overnight.

    I've had to set it to 11.8v so it doesn't shut off randomly, all the while the multimeter confirms it's still well over 12v.

    I bought it from blackboxed.ca but they are ignoring my requests for an RMA, any ideas here?
     
  2. jokiin

    jokiin Well-Known Member Manufacturer

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    where are you measuring the voltage?
     
  3. Fruitflan

    Fruitflan New Member

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    At the point where the cable connects to the PMP box (via the plastic connector - I unplug it to measure). Should I be measuring it elsewhere?
     
  4. jokiin

    jokiin Well-Known Member Manufacturer

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    no that's the right spot, they're generally accurate to around plus or minus 0.1v, if 12v is giving you 12.3 cutoff then check what 11.8v gives you, these are generally too low rather than too high so it probably works in your favour
     
  5. SawMaster

    SawMaster Well-Known Member

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    Are you certain your DMM is accurate? A lot of the cheap ones seem fine with a low battery in them but will actually lose accuracy before giving any clue that the battery is dying. In the end, if the PMP does it's job at the level you want consistently and reliably, the numbers really mean nothing as long as you can translate them to reality. I have an digital FM radio whose display is low by 5kHz, so I just tune 5kHz low and use it anyway- I know where it's really tuned to.

    I do feel a RMA would be appropriate in your case, but the world is full of "other kinds of sellers" who aren't so easy to get along with.

    Phil
     
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  6. jokiin

    jokiin Well-Known Member Manufacturer

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    something to keep in mind also is that the PMP will cut off at whatever voltage you choose, with a plus or minus variance of 0.1v the 12v setting could cutout at anything from 11.9v to 12.1v, once the load is cut the battery voltage will rise and can easily come up another 0.2 to 0.3v, this is quite normal
     
  7. Fruitflan

    Fruitflan New Member

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    Thanks for your replies. I'm pretty sure the DMM is accurate as I can see the voltage in my videos and it corresponds to what I see on the DMM. Also I had the PMP before I replaced the car battery and the DMM helped me identify the battery needed replacement (it was approx 6 years old).

    If there is a surge, i'm wondering why when i disconnect and then reconnect the PMP well after the ignition is turned off, why doesn't the PMP box and LED turn on again?
     
  8. jokiin

    jokiin Well-Known Member Manufacturer

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    the voltage required to restart is generally about half a volt higher than the cutoff point, you need to start the car to get the voltage high enough to turn it back on
     
  9. mannyfresh2500

    mannyfresh2500 Member

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    So with a multimeter we put the positive on which part of the PMP connection and the negative where? I'm trying to measure mine too. I got 12.4 at the battery posts but my cutoff is set to 12v and not powering up the dash cam (LED is off but button is set to ON).

    Thanks
     
  10. jokiin

    jokiin Well-Known Member Manufacturer

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    measure it at wherever you have taken power from
     
  11. SawMaster

    SawMaster Well-Known Member

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    Best to check where the PMP connector is in case something is bad between it and the power/ground taps. On the car side of the connector, take you meter and ground the black lead to the car chassis. Tale your red lead and try each terminal till you find which is 'hot' (it should be very close to voltage measured at the battery). Leaving the red lead there, take the black lead to the other terminal(s) till you have the same voltage. Doing it this way checks both the hot and ground sides as grounds can fail too ;)

    Phil
     
  12. mannyfresh2500

    mannyfresh2500 Member

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    Thanks, everyone.
     

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