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One cell slow to wake up. Your thoughts?

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

  1. kensuf

    kensuf Cave Instructor

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    Throw the cell out.
     
    taimen likes this.
  2. taimen

    taimen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Europe
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    Well the calibration procedure on my unit is very reproducible done even once. But I have noticed that I get 1-2 mV higher readings with a second run. Again very consistently.
    It may be due to oxygen diluting with air or a cell response time issue, but it is consistent. Some divers have noticed the same with newer batches of JJ-CCR cells and think it is due to slower response time of their new cells.
     
  3. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
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    Seems like you already know what to do. Throw it in the cell checker just for your own knowledge/learning, then throw it in the trash
     
    MegDiver792 and rjack321 like this.
  4. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

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    Not getting the same results with 2 calibrations in a row means the calibration sequence or instructions are wrong. 2 calibrations 10mins apart? You need to be getting exactly the same answer. My guess is there is not enough flushing to ensure a 100% o2 content in the loop.
     
  5. Wookie

    Wookie Secret Field Agent ScubaBoard Business Sponsor

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    That rebreather is just waiting to kill you.
     
    MegDiver792 likes this.
  6. doctormike

    doctormike ScubaBoard Supporter Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    So that's a criticism of the Shearwater control process, right? I guess they make some choice balancing accuracy and O2 usage...
     
  7. taimen

    taimen ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Europe
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    Instructions are clear. That is how the unit works. My cells and calibration process have been very stable for 12 months now (new cells just arrived and I will change them all at once, another can of worms).
    Calibrations 10 minutes apart, with loop full of oxygen tend to give the slightly higher value. Starting with air filled loop, it seems to have a tad too short flush.

    upload_2019-11-6_19-0-26.png
     
  8. Norrm

    Norrm Banned

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    I saw the thread title and thought it was about BRAIN cells and a typical Monday morning rant.
     
  9. sunnyboy

    sunnyboy Instructor, Scuba

    # of Dives: 500 - 999
    Location: Vancouver Island, Canada
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    Actually, that may be irrelevant. My unit always looks super clean, but I still have to clean the gold contacts or I get odd cell results. With gold contacts, 'dirty' contacts can look identical to clean contacts. You only know they were dirty after the fact (i.e. after cleaning the odd behaviour goes away).

    The procedure for my unit is: if any cell acts up, clean the contacts before doing any other diagnostic procedure. In my case, 90+% of the time that fixes the issue.

    Calibrations should be repeatable, as stated by many in this thread. Even a bad calibration process should not see only one cell drifting during the dive. If the calibration wasn't effective, then all 3 cells should show the same 'odd' behaviour during the dive. The fact that only cell 3 does this strongly suggests cell 3 is bad.

    Any cell that 'drifts' during a dive is either EOL or faulty and need to be replaced.

    All, of cousre, IMO.
     
    rjack321, MegDiver792 and wedivebc like this.
  10. Valyngar

    Valyngar Nassau Grouper

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    Now just think the probleb, that is you life or aborted dive worth saving 50€/$, when you have already 9000$ machine. Cos of time and gas to divesite is probably already over that. If you already think there might be problem, just fix it and don't wait it happen.
     

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