How many sensors should I replace on rEvo after 8 months of not diving?

[Heat Miser]

I have found the rEvo B cells (manufactured by Vadagraph from what I understand) to be rock solid, to get the rEvo B label the cells are tested for performance by rEvo. I have never had a cell fail in 18 months before it is rotated off the controller, I have never had a cell fail after 24 months (cell position 4). I have had one cell fail after around month 27 (cell position 5) and 2 fail in month 29 (cell position 5), the cells that failed at 29 months I disconnect and dived with 1 cell on the dream until it was time to add the new cell a month later, the cell that failed at 27 months I replaced with a cell that was cycled out earlier that I found to be still functioning well.

What is the differnce between B's and C's (are there A's) I got this C from Belgium last year when things were in short suppply

 

[Wibble]

The problem with calling Wibbles/Revo strategy a once every 6 months replacement strategy (in my mind), is that people get lazy and just put in one new cell every 6 months. And non-rEvo divers say that stupid you have 2.5 year old cells in your rebreather. That's clearly not the policy.

Which is exactly what's happened with my box. It was two years old (and unused) when I bought it. The previous owner had replaced two of the cells. In the 15 months I've owned it, I've replaced all five cells through the "replace broken immediately, replace each six months" policy.

Que the wailing of the "that's 5 cells, more than a JJ would cost" brigade... I just don't care. The cost is irrelevant and having 5 cells means I've a far easier time understanding what's going on on my box.

What is the differnce between B's and C's (are there A's) I got this C from Belgium last year when things were in short suppply

Probably the batches as Revo test them all.

What's the date on the cells?

 

[Wibble]

Not sure if this is of help, this is the checklist I use. Based upon the Revo checklist, but specifically modified for the Petrel controller + Nerd backup.

It's best printed double-sided and two to a page then guillotined in half so it's half letter size (A5) with the build check on one side and the closed check on the other.

 

[Tassi Devil Diver]

What is the differnce between B's and C's (are there A's) I got this C from Belgium last year when things were in short suppply

No idea, only ever seen B's just went through my tin of old cells all 15 of them are B's

 

[Wibble]

No idea, only ever seen B's just went through my tin of old cells all 15 of them are B's

Kind of answers the question of how you dispose of all your old cells!

 

[rddvet]

Revo's recommendation of changing a cell every 6 months is idiotic, especially mid-pandemic when cells can be hard to find and the easily available ones like Oxycheq's suck.

 

[Wibble]

Revo's recommendation of changing a cell every 6 months is idiotic, especially mid-pandemic when cells can be hard to find and the easily available ones like Oxycheq's suck.

And your evidence is...?

The main thing is the Revo has 5 cells split into two completely separate monitoring systems. You've a full backup to complete the dive if the system fails; you've other cells to compare anomalies, so much less cell anxiety.

The point of each 6 months is to keep a churn going. It seems that quite a few of the "I've only got three cells" crowd change them all each year (of none have died in the meantime).

Anyway, the Revo crowd are quite happy with their cell strategies.

 

[rddvet]

And your evidence is...?

The main thing is the Revo has 5 cells split into two completely separate monitoring systems. You've a full backup to complete the dive if the system fails; you've other cells to compare anomalies, so much less cell anxiety.

The point of each 6 months is to keep a churn going. It seems that quite a few of the "I've only got three cells" crowd change them all each year (of none have died in the meantime).

Anyway, the Revo crowd are quite happy with their cell strategies.

Do what you like and what makes you comfortable. I work with oxygen cells regularly in regular life. To change a perfectly good cell way before necessary just doesn't make sense. If you're checking for current limiting and linearity, then dates are arbitrary. In our current situation, it can be hard to get good sensors. You may have a cell that is within all of the limits and working well, but then you change it because that's what the manufacturer says to cover their butts, and you could be stuck replacing it with a brand new cell that sucks. Aka the Oxycheqs. I fall squarely into the group that believe within reason, if you're cells working fine keep using it. It's not like they miraculously stop working after a certain date. On average the cells between the 2 units I own average being in service around 18 months. If they went a little longer or a little less I wouldn't fret. I don't push much past 18 months like some do, just do to my personal comfort level.
At the end of the day it's your choice, but the Revo recommendation imo is overly cautious and is meant to cover the manufacturer's ass more than it's based in solid scientific fact.

 

[stuartv]

Do what you like and what makes you comfortable. I work with oxygen cells regularly in regular life. To change a perfectly good cell way before necessary just doesn't make sense. If you're checking for current limiting and linearity, then dates are arbitrary. In our current situation, it can be hard to get good sensors. You may have a cell that is within all of the limits and working well, but then you change it because that's what the manufacturer says to cover their butts, and you could be stuck replacing it with a brand new cell that sucks. Aka the Oxycheqs. I fall squarely into the group that believe within reason, if you're cells working fine keep using it. It's not like they miraculously stop working after a certain date. On average the cells between the 2 units I own average being in service around 18 months. If they went a little longer or a little less I wouldn't fret. I don't push much past 18 months like some do, just do to my personal comfort level.
At the end of the day it's your choice, but the Revo recommendation imo is overly cautious and is meant to cover the manufacturer's ass more than it's based in solid scientific fact.

If the cells don't fail - as you say is normal - then following the rEvo recommendation would mean using every cell until it has been in use for 30 months (in a 5 cell system - 18 months, if you are only running 3 cells).

How is that overly cautious?

Of course, my statement is based on being in a rotation already. If you buy 5 new sensors and put them all in, then yes, you will replace an almost new cell after 6 months. And one more after 12 months. Next time, you'd be replacing one that is 18 months old - as you said you personally already usually do.

Replacing 2 cells "prematurely" in order to get out of the situation of having 5 sensors all from the same batch does not seem "overly" cautious to me.

 

[rddvet]

If the cells don't fail - as you say is normal - then following the rEvo recommendation would mean using every cell until it has been in use for 30 months (in a 5 cell system - 18 months, if you are only running 3 cells).

How is that overly cautious?

Of course, my statement is based on being in a rotation already. If you buy 5 new sensors and put them all in, then yes, you will replace an almost new cell after 6 months. And one more after 12 months. Next time, you'd be replacing one that is 18 months old - as you said you personally already usually do.

Replacing 2 cells "prematurely" in order to get out of the situation of having 5 sensors all from the same batch does not seem "overly" cautious to me.

Because good cells don't need to be replaced at 6 months. To each his own. I see it differently than others.