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Cell dating question

Discussion in 'Rebreather Diving' started by rddvet, Nov 30, 2019.

  1. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
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    I have a question that didn't come up when discussing replacing cells in class. It's a year since my cells were put into service, so I'm replacing them. I've had a backup cell in my spares box for a few months and plan on putting into service and putting a newer cell into the spares box. The cells are AI cells, and I noticed they have a sell by and a don't use after date on them. I'm not sure if all cells have the same since I've only used AI. The backup cell has a don't use date of July 2020. I would assume as long as it's working fine and has normal linearity, who cares what the don't use after date is? I would think it's a cya thing by the cell manufacturer. Am I assuming incorrectly, and people are taught not to use cells after the don't use after date? It's not like it turns into a pumpkin and stops working after the don't use after date.

    We discussed all of the typical cell replacement issues such as age of cells, using different batches vs not, as well as when to replace cells. For some reason the specific discussion of the "don't use after" date never came up,
     
  2. michael-fisch

    michael-fisch Manta Ray

    # of Dives: 2,500 - 4,999
    Location: Germany
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    I have a calibrated pressure pot that I use for simultanious cell tests of up to 3 cells.
    Narked at 90 has them Cell Checkers | Narked at 90
    as does Tecme.de - look under Tec Equipment für Nitrox, Rebreather Höhlen Tauchen then click on Sensor tester under Sensor / Houses

    Mine is the Tecme model, which outputs the gathered info to Excel. I have cable sets for Coax male, Coax Female, 1/8" Phono male, and 3 Pin Molex so I can test almost any cell up to 2Bar O2, and have printed results as soon as my laptop has access to a priner.
    It's nice to see where and when a cell starts becoming nonlinear/current limited before I notice it during a big CCR dive.
    Since I have 3 different CCR RBs of my own and a Divesoft analyser I end up using it every few months.

    Michael
     
  3. jgttrey

    jgttrey ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Houston
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    Cells are using themselves up whether installed or not. Most have a design life expressed in "percent hours." The actual time at elevated PO2, unless you dive a lot, doesn't accelerate things that much. A year at 0.21 is about 184,000 percent hours. 100 hours at a 1.2 PO2 is only 12,000 percent hours. For most of us, it isn't the dives that are using up our cells, but the time between dives.

    I dont know the "use by" date or how AI calculated it, but best practice is to install within 6 months of manufacture and replace after 12 months or when voltage drops 10% from what it was when you installed.
     
  4. broncobowsher

    broncobowsher Solo Diver

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    Buy 2 now, put them in along with your aged spare. In about 6 months buy 2 more. Replace the oldest and pull one of ones you are buying now and set that aside for a spare.

    That is the start of a cell rotation program. Get a new cell every 3-4 months. The oldest one coming out should have some life left and that turns into the spare. If there is a bad batch, it is just one cell and not all that are going to go wonky on you. The spare cell isn't a brand new one that never gets used either.
     
    kensuf and davehicks like this.
  5. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
    867
    639
    93
    @michael-fisch I bought the narced at 90 mini cell checker. I haven't used it as of yet. I plan to try the cells I'm pulling out of service in it to learn how to use it and then start checking the new cells from time to time. I just planned on doing it every few months when I think about it. A couple people tried saying the high pressure p02 will shorten cell life, but I don't buy that
    @jgttrey The cell will be pretty much within those specs. I'm not sure where the don't use after comes from. I was mainly looking to see if anyone's ever been taught not to use after that date. I figure once it's in service, it doesn't really matter unless it acts odd or tests funky. By the time a year is up the cell will be about 5 months past that date. I doubt it will really lead to any issues.
    @broncobowsher I know it's a debated topic, but I fall on the not rotating side of the fence.
     
  6. broncobowsher

    broncobowsher Solo Diver

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    So your plan it to ignore the manufacturer's do not use after date? Maye test every couple months, if you remember.
    Florida, I know where to expect to read up on the next accident at...
     
    cathal likes this.
  7. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
    867
    639
    93
    Thanks for your help. Really enjoy the douchiness. It’s always shows who’s classy in these threads when someone’s response is how you’ll die/get injured.
     
  8. broncobowsher

    broncobowsher Solo Diver

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    Don't use after date, does it really need to be explained? I didn't think it would need to be, but I have been wrong before.
     
    cathal likes this.
  9. rddvet

    rddvet DIR Practitioner

    # of Dives: 50 - 99
    Location: Florida
    867
    639
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    Again, some of these things are cya for the company. I’m interested to see what experienced divers have been taught in their courses. That specific scenario was not brought up in my course because I don’t know if that’s specific to ai. I also plan to reach out to my instructors but was interested to hear if this has been specifically discussed in anyone’s classes or if anyone has experience with it. I never said I made a decision on what I plan to do, but was commenting that it seems of all tests well it should be ok. A cell doesn’t magically start acting up after a date stamped on the box. I’m interested to see if anyone knows the reasoning for the dating and their experiences with ai or other cells.

    If you have anything else productive to add, I’d be happy to hear it. If you just want to try and make me sound stupid or tell me how I’m going to die then either just stop typing or feel free to pm me.
     
  10. jgttrey

    jgttrey ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Houston
    648
    792
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    @rddvet, does the cell have a date of manufacture on it or the packaging? Just curious.
     

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