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One cell slow to wake up. Your thoughts?

Discussion in 'Rebreather Diving' started by doctormike, Nov 5, 2019.

  1. taimen

    taimen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
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    I tend to run the calibration sequence on my JJ twice. I do get 1-2 mV higher calibration values with the second run. Thus a single calibration run doesn't seem to produce over 99% O2 environment long enough. It is very consistent anyway.
    All my cells have behaved identical, and waiting for replacement. At 12 months all three still calibrate to 50,51 and 50 mV. JJ-CCR cells from Oct 2018.
    I would ditch any cells waking-up during dive or showing any other erratic behaviour.
     
  2. JonG1

    JonG1 Nassau Grouper

    # of Dives: 2,500 - 4,999
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    It would be worth checking connectivity, I have had several issues that intrinsically looked like cell problems but were related to the Fischer cable, also not familiar with the JJ but altitude and ambient pressure have to be accounted for when I am checking my KISS at 1.0.
     
  3. JonG1

    JonG1 Nassau Grouper

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    Also there's a related debate on CCR Explorers FB pg for reference
     
  4. The Chairman

    The Chairman Chairman of the Board

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    Very mild corrosion and dirt can be affected by temperature. I usually plug/unplug my cells a few times to clean off any schmaltz. Obviously, this is below our ability to see it, but it can be an issue all the same.

    How long did you let the cells air out before you started calibrating? I've seen peeps break the seal and immediately start the procedure. Although some say to wait 15 minutes, I allow an hour or more before I expect to get valid results. There can be a variation even after the first dive as the cells get fully lit.
     
  5. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

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    Yeah, was following that. I wish that the CCR tools app was out for OS X or iOs...
     
    JonG1 likes this.
  6. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    Right, and I think THAT is what "wake up" refers to. But I'm talking about something that happens every time I do a build, for a cell that has been installed for months. That's why I was wondering if it was the exposure to O2 that made it not return to it's original (low but in spec air output) and end up in line with the other two.
     
  7. The Chairman

    The Chairman Chairman of the Board

    # of Dives: I just don't log dives
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    If that's the case, even though it's within specs, I would be replacing that cell. When in doubt: toss it out.
     
  8. The Chairman

    The Chairman Chairman of the Board

    # of Dives: I just don't log dives
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    Of course, that would be after I swapped cells around. The thing I like about SF2 cells, is that the spring is on the cells. I don't have to worry about corrosion or dirt getting in places I can't see.
     
    doctormike likes this.
  9. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    Yup, that's what I'll do.

    But I was just wondering about this phenomenon of cell recovery, which seems to be happening pretty consistently. And of course, I wouldn't have even bothered to post this thread if it was actually out of spec in air, but since it is in spec, was wondering if others had seen this...
     
    cathal likes this.
  10. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    See that's the real concern I have here. Is there something with the calibration procedure itself? People have said "PO2 is PO2", but the point is that we are all relying on whatever procedure we use to put 100% O2 on the cell face. If that isn't happening with reproducible precision, then everything downstream is off as well.

    So yeah, easy answer is to just get a new cell, but I think that there is more happening here than just a bad cell. For example, the fact that PO2 in air on build is often a bit off from 0.21. That may be a controller pressure sensor thing, something related to auto vs SeaLvl? But it persists despite a recent service of the controller for a bad pressure sensor. Gonna check with Shearwater and will report back. Maybe the auto calibrate sequence needs a firmware update to give a better flush? Not all units use that...
     

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