Do all rebreathers require a bailout bottle on board ?

[Wibble]

Why would all the other manufacturers tell you to chuck cells after 12 to 18 month if they are still very relibable?

Because they all use only three cells.

Can't use one as you don't know if it's failing.
Can't use two as you don't know which one is failing.
Use three as you don't get many two-cell failures.

Except... on my MOD1 third dive, I had TWO cells fail. How could I possibly know that as a complete novice? Simples; I have the other two cells telling me that one cell was right and two cells were wrong.

(Reason was one wasn't good and the second was slow as some water was on the cell face.)


Yesterday I noticed that one cell was reading a bit higher than the others. 4 vs 1 is fine. Interestingly it's the cell I replaced in February. I will be swapping it to a different position -- onto the Nerd -- and I'll dive it next weekend and keep a close eye on it (like it's on the Nerd...).

On a three cell machine, it's deadly serious. On a five cell machine, less so.

 

[sea_ledford]

Are they really that bad? I personally haven’t experienced nearly enough failures to warrant replacing mine with solid state sensors that cost around 10x the price. I feel like the rate of failure is highly overstated when using cells from a reliable manufacturer.

Even if I did eventually go in that direction I couldn’t see running less than 2 or 3 cells. You’d still need to verify to which one is broken even if the rate of failure is less.

I don’t think the galvanic cells are nearly as bad as people say.

Galvanic cells are horrible. They are barely fit for purpose, and you have extensive training on not to trust them and what to do when they go wonky.

None of my original three cells survived the first year, all of them failed during dives. Replacements did better, maybe it was just a bad batch. But every failure I've had on a CCR was cell related.

I have at least 5 unused, and unopened cells that are expired; 2 were backups that never got installed, 3 were a full set the were replaced during service in Jan of 2020, so never got dove before expiring. That's $500 I'd rather put toward a SS cell that would still be fine.

 

[Subcooled]

Hello divers

Just a random thought that pop into my head. So why do you need a bailout bottle if you have a diluent bottle full of air? Why can't you just flip a switch on your mouthpiece and go to your diluent bottle and use that as an emergency gas to get you to the surface?''

A rebreather is a closed circuit system. You need to add diluent only when you are descending. You don't need that much of it thus.
A return trip without a rebreather could be long, though.
If you dive deep, you might need both bottom gas and decompression gasses to reach the surface.

The bottle line is if i am not diving too deep and have enough diluent gas on board. Maybe this is a dumb question but i can't seem to find an answer. P.S. i am not rebreather certified, but going to very soon.

A look into a Rebreather Bail Out Valve – BOV’s - Mexico Cave Diving & Cave Training - ProTec Blog

The Bail Out Valve or BOV can be a potential life saver when used propperly while diving CCR or PSCR rebreathers

www.protecblog.com

 

[sea_ledford]

On a three cell machine, it's deadly serious. On a five cell machine, less so.

A question I've always had about revos (or any other 4+ cell units): If you have a cell fail during pre-dive checks, can you still go diving with the unit as-is? You are getting in the water with a known failure, which is supposed to be a no-no. But so long as you have at least 3 good cells are you still good to go? What if one of those three good cells is the 2.5 year old one?

Not trying to be a troll, I've just never heard the pre-dive failure protocol.

 

[berndo]

Except... on my MOD1 third dive, I had TWO cells fail. How could I possibly know that as a complete novice? Simples; I have the other two cells telling me that one cell was right and two cells were wrong.

I was taught in mod1 to flush the loop when one cell is acting weird. When you flush with a known gas you know which cell or cells give the wrong reading.

 

[Wibble]

Have a friend with an AP Inspiration who's constantly struggling with cells. It's even stopped him diving once.

Strangely this doesn't seem to happen on my Revo.

A question I've always had about revos (or any other 4+ cell units): If you have a cell fail during pre-dive checks, can you still go diving with the unit as-is? You are getting in the water with a known failure, which is supposed to be a no-no. But so long as you have at least 3 good cells are you still good to go? What if one of those three good cells is the 2.5 year old one?

Not trying to be a troll, I've just never heard the pre-dive failure protocol.

I've never had a cell fail on the boat when doing the pre-breathe.

OK, yet.

The Revo cells are arranged as 1, 2 & 3 are on the Petrel controller. 4 and 5 are on the Nerd (or RevoDreams which are stand-alone monitors with HUD flashy lights). In theory, it's possible to dive with one dud cell on the Nerd as the controller will use 2:1 voting logic for injecting O2. However, the Nerd is the backup to the Petrel controller, so with only one cell you've no comparison should the Petrel die.

Others may have more pertinent experience.

 

[flymolo]

Galvanic cells are horrible. They are barely fit for purpose, and you have extensive training on not to trust them and what to do when they go wonky.

None of my original three cells survived the first year, all of them failed during dives. Replacements did better, maybe it was just a bad batch. But every failure I've had on a CCR was cell related.

I have at least 5 unused, and unopened cells that are expired; 2 were backups that never got installed, 3 were a full set the were replaced during service in Jan of 2020, so never got dove before expiring. That's $500 I'd rather put toward a SS cell that would still be fine.

I would agree that galvanic cells weren't originally designed to go in rebreathers but I personally wouldn't say they are horrible. For the most part I've had few issues and I rarely give them much thought at all.

 

[broncobowsher]

A question I've always had about revos (or any other 4+ cell units): If you have a cell fail during pre-dive checks, can you still go diving with the unit as-is? You are getting in the water with a known failure, which is supposed to be a no-no. But so long as you have at least 3 good cells are you still good to go? What if one of those three good cells is the 2.5 year old one?

Not trying to be a troll, I've just never heard the pre-dive failure protocol.

If you know it is bad you should fix it.
But.............
I have done it to diagnose cells. Something isn't as happy as it should be. Move some cells around (typically putting the questionable stuff on the NERD) and go do a dive. While not going for a 3½hour deco dive a regular recreational dive is good for figuring what is going wrong. Being on the NERD I didn't have it on the controller. The controller was now full of happy cells. the NERD had one cell that matched what was on the controller and one cell that reads wonky (high in this case). The NERD could see there was a split and would calculate deco based on the low cell and OX loading on the high cell while being pissed about it. Finished the dive and confirmed the cell was not happy. Really not much different than running a controller and a single DREAM.

On a 3-cell system the best I could do is rotate the cells and see if it follows the rotation. When you need to dive to confirm the problem that leaves you with only 2 good cells. Now if you did the batch purchase it could be a pair of cells failing in unison.

A man with 5 watches may never know exactly what time it is, but they can sure tell when one of the watches is broken. I have a clock in the oven and one in the microwave. Both are GE appliences and built at the same time. Those two clocks are always in sync. They both drift in unison. Eventually they don't match the wall clock. Which is wrong? The pair that drift together, or the one that runs by itself? That single wall clock holds time a lot better than the pair on the oven and microwave, until the battery dies. Then it goes way off. At which point I start pulling out clocks number 4 and 5 to figure out what 1,2, and 3 are really doing,

 

[kensuf]

It's great to have all 5 cells displaying so you can compare them and make informed decisions.

Even enables handling two concurrent cell failures; something which would throw a three-cell system into a tailspin -- probably out voting the one good cell.

Bottom line: Revo divers are very happy with replacing fewer cells and using consuming half the lime as other rebreather divers.

I have had two bad cells vote out a good one. Not fun, but manageable.

 

[Degenerate]

Have a friend with an AP Inspiration who's constantly struggling with cells. It's even stopped him diving once.

Strangely this doesn't seem to happen on my Revo.


I've never had a cell fail on the boat when doing the pre-breathe.

OK, yet.

The Revo cells are arranged as 1, 2 & 3 are on the Petrel controller. 4 and 5 are on the Nerd (or RevoDreams which are stand-alone monitors with HUD flashy lights). In theory, it's possible to dive with one dud cell on the Nerd as the controller will use 2:1 voting logic for injecting O2. However, the Nerd is the backup to the Petrel controller, so with only one cell you've no comparison should the Petrel die.

Others may have more pertinent experience.

And I have no friends who have struggled whatsoever with their cells in the APs.
If one sucks just chuck it and throw in a new one.

If 5 cells are better than 3 then obviously 7 would be better than 5.
How come your revo doesn't have 42 cells?
More seems to be better, just to be safe you know.

Come on, if you're actually paying attention to what your CCR is telling you during a dive then 3 cells is enough.