Cell health

PeterN

PeterN

Active Member
A sad sad post by Jont about the loss of a rebreather diver due to having two bad cells vote out one good cell has me wondering about best practices for cell validation.

I have had good instruction and great advice, but would appriciate from those of you with more time in what you do to prep for your dive, and when in the water, what then?

I would love to see a one page sheet of non rig specific how to have a happy cell relationship.

Thanks,

Peter
 
This is what I do :

- every 3 months the cells go into a cell checker. Permits to see if the cells are going to fail sometime soon or spot on.
- on every dive I only add O2 to the rebreather and the adv is off until I get to 6meters and check the mv of the cells. If the values are good then I'm good to go else dive is ended and cells get a run in the checker.
Some do the same at the end of a dive but I don't.

This works for me but might not for you depending on your dive profile.

Envoy***233; depuis mon GT-I9100 avec Tapatalk
 
Jeff Pack said:
Turn off your O2, dil flush, and you should should know at a given depth what your PPO should be.
Click to expand...

This will only show That Cells are telling the truth at the ppo2 of the DIL at that depth. I aim for DIL ppo2 at bottom phase of 1-1.15 ...
The DIL flush will not show up a cell current limited just below your setpoint of 1.2 Or 1.3 depending on preferences.

I recommend the 6m check, then a lil manual add of o2 every 20mins to prove to you the cells can read above what your CCR is trying to maintain. If you add a bit of o2 and only one cell increases, you have a serious problem!

I also run by the personal rule that if any one cell goes outside of the 0.2-1.6 range and I can't get it back in that range, whether it's voted our or not I'll bailout. No exceptions
 
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PeterN said:
A sad sad post by Jont about the loss of a rebreather diver due to having two bad cells vote out one good cell has me wondering about best practices for cell validation.

I have had good instruction and great advice, but would appriciate from those of you with more time in what you do to prep for your dive, and when in the water, what then?

I would love to see a one page sheet of non rig specific how to have a happy cell relationship.

Thanks,

Peter
Click to expand...


SET UP

I am not going to bother talking about MV tracking because thats something i stoped doing a while back. Pre dive on the bench at home ill asemble the rig and do a neg check. Then I switch on the display to show me the PP02 in air.

I am expecting 0.2-0.25

Then I o2 flush and i am expecting to see .98.98.98 +


If a cell is a fraction out Ill ignore it but if its significantly out ill strip the unit, check all wire conections, cleen the cell conections, re asemble and check it again. Neg then 02 flush. If still out ill swap the cell to another position to see if the fault folows the cell.


Once i am happy ill either dive the unit as is or Ill calibrate it and make note of the suspect cell.

In the last year i have probably calibrated my unit two or three times max.


ON THE BOAT

As part of pre dive routeen ill switch from 0.19 to 0.7 set point and watch the unuit hit set point. Then Ill 02 flush and If i dont see .98.98.98. I dont dive


IN THE WATER

Manual flush pure 02 then jump in. Get to shot squirt in more 02 and decend to 6 ish M where my buddy and i will do a fly by bubble check I hceck him, I go past him he checks me all as we decend.

Once past 6m I will inject 02 and ensure my hand sets read well over 1.6. Ill spike to 1.8 or sometimes even 2.0

Ill then vent (one full breath only) and suck in dill (which tests ADV and decend on the Scamerhorn slide on low set point.

On reaching the bottom of the shot I will know my depth and the PP02 i should be on at that depth. This validates my cell PP02 readings. Ill then switch to high set point and watch the unit acheive 1.3

Then i go diving


During the dive at 10-15min intervalls ill squirt in 02 tio say 1.4 just to check my cells are not maxed out.

If the cells are reading odd or if i feel weierd for any reasion Ill switch to low set point and flush with dill to confirm cell readings against a known PP02 and spike 02

If still in doubt ill flush with dill or run the unit manualy on low set point or id bail to OC and go home.

On every dive i spike the 02 cells at the 9m stop (1.8 - 2.0) just before scending to 6m


ATB

Mark
 
The catious hyperoxic cell test perhaps is:

Test your bailout system(s) ! while descending to 10m (or more)
with 100% O2 in loop.
Check linearity while descending.
Add oxygen to prevent CL bottoming.

Ascend to 6m and go CC.

This method beats a cellchecker validation because:

-moving cells around increases the possibillites of failures.
-Cell validations in a cell checker are ALWAYS old.
"Funny - they worked so nicely yesterday"

Regards
Sven Becker
 
Peter,

Just like at the Meg factory... cells ought to be tested in a hyperbaric pot (cell checker) regularly. There's no real equal to this. You can make a cell checker for less than $50. No excuse not to use one. You can re-validate this on the dive, but you should jump in knowing that they are linear to 3.0 PP02.


Dave

.
 
Dave Sutton said:
Peter,

Just like at the Meg factory... cells ought to be tested in a hyperbaric pot (cell checker) regularly. There's no real equal to this. You can make a cell checker for less than $50. No excuse not to use one. You can re-validate this on the dive, but you should jump in knowing that they are linear to 3.0 PP02.


Dave

.
Click to expand...

Thanks Dave, I have a cell checker. I am not inclined to use it often, but wonder if others use theirs on a schedual or interval like a planned cell rotation.

Peter
 
I don't do much, but I class what I do do as essential.

First, before set-up I switch on and check the cells in air - should be 0.21 since last calibration. If I get 0.20, 0.21, 0.12 then cell 3 is iffy.

Assuming all is OK, set-up and calibrate. I then take note of the end-cal values. In an Inspiration they represent a normalised mv reading in air with a decimal-point offset - so this information is valuable. They ought to achieve the same values each time (I calibrate each dive). So 0.98, 0.95, 1.12 would mean 9.8mv, 9.5mv and 11.2mv. As I recall the last values these should not change (I notice they rise as the cell starts to die). If #3 doesn't make 11.2 but instead get to say 0.95 then this is representing a potential issue too.

Assuming all OK I am good to do my final checks.

Sat at 0.98 on the display blow some dil in and check 3 things - low PO2 alarm, reaction times similar/all moving and controller restores to 0.98 quickly.

All OK - time to dive.

At the end of the dive I make a current-limit check - 8m, 1.6-1.7 quickly seen on all cells.

Matt.
 
Hi Matt,

in my opinion it makes more sense to check current limitation at the beginning of a dive then at the end.
there is , if not repeated dives on the day, to much time between .
I check when reaching final depth after setting to high setpoint and spiking to 1.4- 1.6.
 
PeterN said:
Thanks Dave, I have a cell checker. I am not inclined to use it often, but wonder if others use theirs on a schedual or interval like a planned cell rotation.

Peter
Click to expand...


I now do a 30 day hyperbaric check during diving season.

Cells are discarded every 12 months no matter what.

There's no reason to push cells. Buy the best and buy them often. Three cells cost less than a good day of offshore boat charter.


Dave

.
 
PeterN said:
A sad sad post by Jont about the loss of a rebreather diver due to having two bad cells vote out one good cell has me wondering about best practices for cell validation.

I have had good instruction and great advice, but would appriciate from those of you with more time in what you do to prep for your dive, and when in the water, what then?

I would love to see a one page sheet of non rig specific how to have a happy cell relationship.

Thanks,

Peter
Click to expand...

Hi Peter,

Assuming that the unit build up was done properly I jump (or sit in the water) with 100% in the loop and breathe that down, I view it as an additional "pre breathe".

Then drop to 15 -30 feet depending on convenience, at ginnie its more like 18 feet to the sand in Devils Eye. Once here I flood the loop with 02 and watch not only the controller but all monitoring equipment so I know the cells and electronics are acting properly.

Here I also perform additional checks, BO, lights, etc, make sure everything is where it should be and that my head is in the game, I called 3 dives on my last cave diving trip at this point for no other reason then "a gut feeling".

Once I'm done with that I flood with 02 again, then dil flush and begin the dive.

During the dive I dil flush every once in a while and monitor my handset once every 30 seconds but that's instinct at this point.

At the end of the dive I play with PO2 quite a bit and basically create an 02 rebreather at 20 feet and up.

I exit with 100% in the loop.
 
Dave Sutton said:
Peter,

Just like at the Meg factory... cells ought to be tested in a hyperbaric pot (cell checker) regularly. There's no real equal to this. You can make a cell checker for less than $50. No excuse not to use one. You can re-validate this on the dive, but you should jump in knowing that they are linear to 3.0 PP02.


Dave

.
Click to expand...

How is this possible Dave for this price?
Tony
 
Elmi said:
Hi Matt,

in my opinion it makes more sense to check current limitation at the beginning of a dive then at the end.
there is , if not repeated dives on the day, to much time between .
I check when reaching final depth after setting to high setpoint and spiking to 1.4- 1.6.
Click to expand...

I don't disagree. However, when on a trip, the end of one dive is quite close (few hours) away from the start of the next - so I do not class it as that important. In my experience current-limiting isn't something that ebbs and flows, it's a characteristic of an old cell - I don't dive old cells so for me this is an ongoing confirmation of health.

I fully agree that you can do these checks on the dive portion, but I tend not to - I try and keep that part for the fun not the checks.

Matt.
 
PeterN said:
Thanks Dave, I have a cell checker. I am not inclined to use it often, but wonder if others use theirs on a schedual or interval like a planned cell rotation.

Peter
Click to expand...

This is one area in which the HH design is superior. The sensor carriage on the HH simply unplugs and then can be plugged into a mating connector in the pressure pot. This takes less time them changing a single cell.

It is similar on my HammerMeg in that the entire sensor carriage comes off with cell intact but I have to unplug 6 small bananas connectors.

John
 
jkaterenchuk said:
This is one area in which the HH design is superior. The sensor carriage on the HH simply unplugs and then can be plugged into a mating connector in the pressure pot. This takes less time them changing a single cell.

It is similar on my HammerMeg in that the entire sensor carriage comes off with cell intact but I have to unplug 6 small bananas connectors.

John
Click to expand...

While that sound apealing, it results in many more connection points. I am curious as to weather HH owners of older rigs require maintanence in this area.

Peter
 
PeterN said:
While that sound apealing, it results in many more connection points. I am curious as to weather HH owners of older rigs require maintanence in this area.

Peter
Click to expand...

As a Hammerhead owner of both the older classic head and now the extreme head Kevin came out with the easies way to check the cells and not even have to remove the cells from the head. This was reassuring since Teledyne quit selling to divers and the other brand cells I was using was a crap shoot. Kevin came up with the Remodulator which is a highly accurate pressure gauge which converts pressure to PPO2. Here is a picture of a HH with the cells being tested to 2 atmospheres.
ImageUploadedByTapatalk HD1362337258.163307.jpg


Sent from my iPad using Tapatalk HD
 
jkaterenchuk said:
This is one area in which the HH design is superior. The sensor carriage on the HH simply unplugs and then can be plugged into a mating connector in the pressure pot. This takes less time them changing a single cell.

It is similar on my HammerMeg in that the entire sensor carriage comes off with cell intact but I have to unplug 6 small bananas connectors.

John
Click to expand...

Very true, now if JM could do something about the failure rate they may be worth diving.......5 out of 6 hammerheads failed during the last cave trip......
 
SlowDiver said:
As a Hammerhead owner of both the older classic head and now the extreme head Kevin came out with the easies way to check the cells and not even have to remove the cells from the head.
Click to expand...




Same thing can be done with any OTS rig, all you need to do is to buy a pair of the hose connector threaded fittings for the hose attach points, and then make up a pair of plugs to replace the hoses. Thread them, T them, and add whatever gas supply and relief system you want to make. Drop the head on without a scrubber installed and knock yourself out. You really want a gas inlet with a needle valve and pressure guage on one side and a relief valve, needle valve for slow depressurization, and a sample-port for sampling 02 out of the other. Flush 02 in at 1 atmosphere until 02 is seen by analysis exiting the other side and then close off the bleed and pressurize with 02 to a known pressure while watching the displays. At 14.7 PSI you ought to see 2.0... piece of cake.

It's easier just to use a cell checker, although you can watch the solenoid bring the PP02 up to setpoint doing this. Basicaly you leave the thing at 1 atmosphere with 02, then turn on the head and let the solenoid fire (pressurizing the entire system) until the PP02 is seen at setpoint (1.2 or so). This is a real system test for those who want to invest a few bucks into the plugs for the head. This is typical bench-test gear.


No real reason to do it though, unless you don't trust the actual electronics and want to test them at the same time as you check your cells.

Probably this is why JM has one... :naughty:


Dave


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