Powering an action camera to take timelapse pictures: low battery signal

Discussion in 'Power Electronics' started by hydrocynus, Oct 20, 2016.

  1. hydrocynus

    Thread Starter New Member

    Oct 20, 2016
    3
    0
    Hello,
    I am trying to setup an action camera (cheap SJ7000) to take timelapse pictures underwater for a couple of week in the field.
    I bought a 12v to 3.7v converter, removed the battery and then soldered the + and - of the battery to the converter leaving the center pin alone and insulated. The camera powers up but because it cannot test the battery, it is shown as empty and the camera powers off.

    How do I prevent this from happening? I cannot use the USB port (camera goes in PC or storage mode, no firmware update can fix this). Can I keep the battery plugged in and then have the equivalent of two batteries in parallel?

    Thanks for your answers!
     
  2. hydrocynus

    Thread Starter New Member

    Oct 20, 2016
    3
    0
    Update. I have cannibalized the battery and kept the circuit board, then connected the connectors to the + and - of the 12v to 3.7v converter and I still get the battery error. Now, testing the battery itself gives me 3.93v vs 3.76v for the converter.
     
  3. crutschow

    Expert

    Mar 14, 2008
    19,528
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    Is there any way to bump up the voltage of the 3.7v converter?
    Can you post info on the converter or a link to it?
     
  4. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    7,402
    1,220
    Sounds like the camera is measuring the battery as low voltage, it probably needs 3.9v,

    can you show a picture / model of the converter and also what happens if you leave the battery and the converter connected?
     
  5. Alec_t

    AAC Fanatic!

    Sep 17, 2013
    8,615
    1,959
    What signal (volts, pulse, ...) would that centre pin have provided in the original camera setup?
     
  6. hydrocynus

    Thread Starter New Member

    Oct 20, 2016
    3
    0
    Hello all, sorry for the late answer. The problem was indeed that the camera looks at the voltage of the battery and it is indeed 4.2-4.3V when fully charged. So I bought some off amazon (5 for 8 bucks!) that are made for Arduino and they work great (no overheating after testing for 12h).

    One thing that worries me is that the timelapse will fill 30GB of the video card if I take one picture per second for 7 days and if there is something that cut the wire to power the camera, then I lose the entire movie. I tried to simulate this scenario and the video cannot be retrieved even with the proper software.

    So, I have decided to mount in parallel the battery and the 12V battery with the buck converter. My hope is that if the wire is cut I can still get the video footage as the inside battery would drain slowly and then save the video when almost empty.

    So, is it possible to mount two batteries of two different capacities in parallel? the buck converted is connected to the + - of the inside battery and to the external 12v battery (120ah).

    Oh, and plugging the buck directly to the + - of the camera works. So this center pin is likely used to recharge the battery. I have not tested this.

    Here are the buck converters I use:
    does not work: https://www.amazon.com/gp/product/B00C0K0WYW/ref=oh_aui_detailpage_o02_s01?ie=UTF8&psc=1
    does work. : https://www.amazon.com/gp/product/B014Y3OT6Y/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1


    Thanks!
     
  7. crutschow

    Expert

    Mar 14, 2008
    19,528
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    You generally can't connect two batteries in parallel if they are different.
    You could isolate them to drive the same load if you use a Schottky diode in series with the output of each.
     
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