One cell slow to wake up. Your thoughts?

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I was taught 3% deviation from expected at 1.0

Which is going to get bigger once you get to ppO2 1.2-1.3

Your 8% deviation at 1.0 will be 20% larger at 1.2 (0.096 or almost 10%) A 10% deviation means your 1.2 is really 1.3. That is too much.

PS your cell quality is awful. You need a better supplier

So you think that it's the cells? I'm really at a loss here.

These are JJ Vandagraph cells, straight from the US JJ distributor in two cases (two different US distributors over the years). At one point I used AI cells from DiveGear Express, but they were very wonky and I replaced them. So this is why I was wondering how accurate the auto-calibrate system is in terms of getting a good 1.0 flush over the cells, since other units don't rely on that. Could it be that your stricter deviation requirements require a better calibration sequence?

Any suggestions? This is not a one off. I have a lot of data over the years.

Thanks for the help...
 
92% of expected is way out of line to me. Mine are usually 98-99% of expected until they get >9months old then it drops to 96-97%.

Do you have a Narked cell checker? I wonder if your loop is <99% O2 so your not reaching expected because expected is actually incorrect (i.e. if your loop is 96% O2 then getting 95% of expected "100%" mV is reasonable)
 
yeah, that was my point about the calibration sequence.... maybe will post in the JJ FB group.
Corrosion on your wiring or contacts will also mess with your voltages. You need to check the cells independent of the RB if 95% of expected is "normal" for you.
 
Corrosion on your wiring or contacts will also mess with your voltages. You need to check the cells independent of the RB if 95% of expected is "normal" for you.

the unit is very clean and this has been from the beginning, but that’s a good point. Will try the cell checker (although I have the mini checker which uses the rebreather head)
 
the unit is very clean and this has been from the beginning, but that’s a good point. Will try the cell checker (although I have the mini checker which uses the rebreather head)
Its a start, at least you'll be positive about the gas on the cell faces.
I flush my mini checker at least 8 times, air seems to hide in the crevices
 
So how do you explain what I am seeing with cell #3? Seriously, I'm not being snarky, I'm trying to learn.


.

You likely have a bad cell or there is a bad connections. Waking up a cell is not a thing, unless it had been deprived of any oxygen for a period of time which even then the effect is minimal.
 
I was taught 3% deviation from expected at 1.0

Which is going to get bigger once you get to ppO2 1.2-1.3

Your 8% deviation at 1.0 will be 20% larger at 1.2 (0.096 or almost 10%) A 10% deviation means your 1.2 is really 1.3. That is too much.

PS your cell quality is awful. You need a better supplier
you need to discuss mv not PO2 since the calibration factor can also be called into question. A leak in the loop allowing air intrusion can throw off a calibration.
 
you need to discuss mv not PO2 since the calibration factor can also be called into question. A leak in the loop allowing air intrusion can throw off a calibration.
I think there's air in there.

My point was that an 8% mV deviation from expected mV at calibration leads to a 0.1 ppO2 error.
 
To the OP,
While online debate about cell behaviour characteristics can be a worthwhile pastime, for long term sustainable safe rebreather operations keep things as simple as possible, in line with a couple of contributors to this thread if there’s a doubt about the cell and it’s under warranty then just replace it. No amount of online discussion will fix the cell or eradicate the doubt for you as it’s a mission critical component. You have a 3 cell unit, you need each cell to be operating correctly, one of them isn’t, replace it.
 
https://www.shearwater.com/products/swift/

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