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Thread: How O2 cells die

  1. #21
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    Re: How O2 cells die

    Quote Originally Posted by kaj crucq  View Original Post
    what if you buy cells for example 3 or 4 months after fabrication? does that means you have to replace them after 12 months from fabrication, or 12 months from purchasing them? (I'm at the point that I have to replace cells for the first time since I bought my CCR :) )


    other point: Who is using a "cell log"? at the end of the dives I mostely do indeed a cell check on 1,6 ppO2. I have a logfile where I write all the millivolts from my cell checks. wWould that be usefull or are these useless statistics?
    AFAIK both AP and N@90 say 12 installed use or 18 months from manufacture, whichever comes first.

    I don't use a cell log. A dying cell can operate perfectly in the 0.2-1.3 range and then crap out at 1.4 and a cell log won't show that.

  2. #22
    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: How O2 cells die

    Quote Originally Posted by Captain Starfish  View Original Post
    AFAIK both AP and N@90 say 12 installed use or 18 months from manufacture, whichever comes first.

    I don't use a cell log. A dying cell can operate perfectly in the 0.2-1.3 range and then crap out at 1.4 and a cell log won't show that.

    For me it goes like this

    I buy three cells

    I use last years old spare cells to replace the “year in use” cells in my unit and the three new cells become my spare cells

    My cells could be 18 months old at the point I open the pack and install them as hopefully they were less than 6months old when I bought them and I have had them in my spares box for 12 months

    I have worked this way since 2004

    I have only once had a cell die of old age. It was my last AP Bud cell I hung on to for 18months in use and was getting on for 3 years old from date of manufacture when it failed

    I hung on because I was awaiting APs replacement cells

    ALL my other cell failures were on cells less than a year old from manufacture

    ALL of my other cell failures were on brand new installed cells or cells less than 3 months in use

    I may be exaggerating when I say three months. Its likely they all failed in the first two or three dives from new. I am trying to remember ones that lasted a few months then failed but I can’t

    When I replace cells (April just before the season kicks off properly) I do so to avoid cell failures on dives which would cost me a dive. I have never considered cell failure in its self to be anything apart from an expensive frustrating annoyance

    I can’t remember ever replacing cells in April when the cells weren’t working great when I binned them


    Better brains and more risk averse (read more sensible) people than I deem diving old cells as dangerous?

    I don’t

    I have had enough cell issues in the last 12 years to know they are not clever or stealthy in any way. Cell issues are usually blindingly obvious. It’s how we react to the issue that defines the risk

    You would be mad not to change your cells every 12 months because a cell fault could cost you a dive

    You would be more mad to believe changing cells every year or every six months if you like, protects you from the risk of cell failure in any way.

    The possibility for all three cells to fail in such a way as to provide what appears to be perfectly valid safe perimeter diving during a dive probably does exist. But that’s right up there with the probability ill kept killed by a great white on my next dive.

    If I took it seriously, i'd not dive again.

    I AM NOT SAYING dive old cells. Doing that is just stupid. In comparison to the cost saveing for gas diveing a CCR cells are cheep

    Please understand my point is NEW CELLS ARE NO GUARENTEE OF CELL FUNCTION





    ATB
    Last edited by Mark Chase; 21st July 2016 at 21:29.

  3. #23
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    Re: How O2 cells die

    +1 Mark


    I haven't had a cell actually fail yet in 3 years. The Mv reading just gets steadily lower until the point where my pathfinder locks out the calibration. It is the only lockout that ISC seems to have added to their system. I'm not sure where it activates, but 7 mv in air is too low. They want to see 9 mv +, but I have had cells calibrate somewhat less than that.

    I recently tested my 3 oldest cells ranging from 3 years old to 1 year old. They were all perfectly linear up to pO2 of 2.0, and held that for at least an hour. I would have done a pool or just changed one or two, but the calibration locked out as the mv in air was just above 7 on all three.

    I think that it is better to have a mfg date/useage range despite the low mv. Infant mortality syndrome seems to be just too big a risk for O2 cells. Sadly, due to the lockout, I had to replace all three at once. These new ones started out at 9 to 10 mv... I'm guessing that they won't last long as the other ones started at ~12...

  4. #24
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    Re: How O2 cells die

    I've had a run of AP14s, one after another, that were just shite on arrival. Yes they replaced them each time but it's a $25 return post fee from Perth to Cornwall so it was hardly a "free" replacement.

    One measured 250mV in air as soon as I took it out of the packet. Others failed within one or two dives.

    I gave up and went to N@90. Solid (for me, so far) cells. Failure mode is usually the 'standard' where they just get slower to respond as they age, then they start limiting lower and lower.

    I have tried to rotate my cells rather than replacing them all in one hit. The idea being that increases the chance that if one is voted out, chances are much reduced that two are failing together.

    Generally, though, if a cell hasn't died on me in the first month I've had it installed it's pretty good for the next 12. Biggest hassle I have is the 'permanent' marker on the cells washing off over time so I lose track of how long the things have been in there.

  5. #25
    So many CCR So little etc Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase has a reputation beyond repute Mark Chase's Avatar
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    Re: How O2 cells die

    Quote Originally Posted by Captain Starfish  View Original Post
    I've had a run of AP14s, one after another, that were just shite on arrival. Yes they replaced them each time but it's a $25 return post fee from Perth to Cornwall so it was hardly a "free" replacement.

    One measured 250mV in air as soon as I took it out of the packet. Others failed within one or two dives.

    I gave up and went to N@90. Solid (for me, so far) cells. Failure mode is usually the 'standard' where they just get slower to respond as they age, then they start limiting lower and lower.

    I have tried to rotate my cells rather than replacing them all in one hit. The idea being that increases the chance that if one is voted out, chances are much reduced that two are failing together.

    Generally, though, if a cell hasn't died on me in the first month I've had it installed it's pretty good for the next 12. Biggest hassle I have is the 'permanent' marker on the cells washing off over time so I lose track of how long the things have been in there.


    Good point I didnt note

    I also replace my cells one at a time over a few dives rather than all at once

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