Cells....

netmage · 17th December 2007, 20:30

Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering.....

Previous owner installed a new cell when I took possesion and labelled install dates on the cells...
#1 - 2/07 - s/n 60844871
#2 - 12/07 - s/n 71120735
#3 - 2/07 - s/n 60844872
-------------------
When I pull up System Monitor (from the secondary) I see the following:
.22 9.7
.22 12.7
.20 8.7

Unit was calibrated a bit over a week ago over at Padipro's...

Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...?

Should I recaibrate and pull values again...?

Training is the end of next month; how many spares should I have on hand...

-Tim

JonnyB · 17th December 2007, 20:42

I would flus the unit in 100% O2 and et the new mv.
Take the mv from air calibration and multiply by 4.7 to see if it is somewhat linear.
If it is linear you do not need to recalibrate.

/Jonny

Quote: (Originally Posted by netmage)

Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering.....

Previous owner installed a new cell when I took possesion and labelled install dates on the cells...
#1 - 2/07 - s/n 60844871
#2 - 12/07 - s/n 71120735
#3 - 2/07 - s/n 60844872
-------------------
When I pull up System Monitor (from the secondary) I see the following:
.22 9.7
.22 12.7
.20 8.7

Unit was calibrated a bit over a week ago over at Padipro's...

Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...?

Should I recaibrate and pull values again...?

Training is the end of next month; how many spares should I have on hand...

-Tim

Janos · 17th December 2007, 20:42

Quote: (Originally Posted by netmage)

Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering.....

Previous owner installed a new cell when I took possesion and labelled install dates on the cells...
#1 - 2/07 - s/n 60844871
#2 - 12/07 - s/n 71120735
#3 - 2/07 - s/n 60844872
-------------------
When I pull up System Monitor (from the secondary) I see the following:
.22 9.7
.22 12.7
.20 8.7

Unit was calibrated a bit over a week ago over at Padipro's...

Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...?

Should I recaibrate and pull values again...?

Training is the end of next month; how many spares should I have on hand...

-Tim

If it's in range don't worry about it. Each cell has a different voltage. You could have three cells at 9mV, or three at 12mV, or a mixture of both and somewhere in between.

Don't worry about it.

Janos

Gilles · 17th December 2007, 21:24

Quote: (Originally Posted by JonnyB)

I would flus the unit in 100% O2 and et the new mv.
Take the mv from air calibration and multiply by 4.7 to see if it is somewhat linear.
If it is linear you do not need to recalibrate.

/Jonny

Or to be a little more exact, take

mV(air) x (O2 purity)/0.209= mV O2

If the actual mV O2 is higher thanthe calculation, then Bob's your uncle. If it is consistently less, and you're unable to get to 1.6 or so @ 6m, then Bob's your aunt, and you want to do something about it.

Given your air mV are above 8mV, and your within .19-.23 in air, I'd have a good first impression.

Currently grounded (again) for no cells

. Life in the tropics can be a PITA.

***ScubaDadMiami*** · 18th December 2007, 00:29

You will frequently find variations in cell MV. This will be the case even from cells that are coming from a new batch. If you can get a calibration and then close to 1.6 PO2 on a 20 foot flush with a reasonable response time, you should still be good to go.

When you get to a year, the smart move is to change even if they are reading well still. However, you might want to consider changing one in month 11 and one in month 12 out of the two that you have there. This will lessen the chance of putting two bad cells in at the same time.

BTW, as you will find, there will be a spread between cells after a while during the dive. So long as the spread is not very big, that is normal. Cells are among the weakest link in the rebreather equipment.

Mark Chase · 18th December 2007, 08:20

I got all keen and mapped the Mv output of my cells for a while (I dont bother now).

I found they started out low then got higher and higher as they got older. My hammer head would often reject new cells. I soaked the cell in 02 over night then i managed to get it working in the HH next day.

I do this all the time now with new cells. I leave them in a bag of 02 for 24hours before I install them.

I have a cell from 2005 thats still chucking out 12mv and works fine. I only use it for testing stuff and its on the bench in between use not stored in a bag. It did 12months in my CCR first.

I had some cells that wouldn't calibrate in the HH even after a soak. The MV output was too low. These cells failed very quickly. One was found to be current limited on the first dive.

Martin Parker said it was the Hammer Heads fault and there was nothing wrong with the cell. This was rubbish because I got the same output readings on the Classic head.

ATB

Mark Chase

netmage · 18th December 2007, 13:21

Ok, so a few PM's talking about cell checkers and linear testing had a little light bulb go off this morning... I havn't quite decided if it's halogen, led or 35W HID.... or a flooded scout..

These cell checkers are basically a pressure pot right? A chamber that can be pressurized, flooded w/ O2 and milivolt's read off the cells...?

The expensive 'guts' are already in the meg itself... Why not something like caps that threads on, tap one for a valve and quick disconnect for O2 feed and the other for an IP guage....? Maybe a bleed valve to vent the original air from the chamber....

I'd have to imagine +.6 ata wouldn't hurt the unit...

-Tim

JonnyB · 18th December 2007, 13:42

Quote: (Originally Posted by netmage)

I'd have to imagine +3 ata wouldn't hurt the unit...

Dont say that!
I recal a certain incident...

/Jonny

O.C.Diver · 18th December 2007, 13:47

Quote: (Originally Posted by netmage)

Ok, so a few PM's talking about cell checkers and linear testing had a little light bulb go off this morning... I havn't quite decided if it's halogen, led or 35W HID.... or a flooded scout..

These cell checkers are basically a pressure pot right? A chamber that can be pressurized, flooded w/ O2 and milivolt's read off the cells...?

The expensive 'guts' are already in the meg itself... Why not something like caps that threads on, tap one for a valve and quick disconnect for O2 feed and the other for an IP guage....? Maybe a bleed valve to vent the original air from the chamber....

I'd have to imagine +3 ata wouldn't hurt the unit...

-Tim

If I'm reading you right.

A 6" diameter scrubber will have about 28 square inch surface area.
Putting a 2 ata positive pressure in the scrubber can will yield 29.4 psi of pressure.
There will be 830 pounds of force trying to blow the lid off your scrubber.
Sounds like latch failures and a posthumous Darwin award.

Ted

netmage · 18th December 2007, 13:50

Quote: (Originally Posted by JonnyB)

Dont say that!
I recal a certain incident...

/Jonny

Got a link?
I got overzealous in my math 3ata would be 60'..., so... 1.6 ata would be 20'

17th December 2007, 20:30	#1 (permalink)
netmage Hello Kitty...... Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2005 Location: Coconut Creek, FL Posts: 352	Cells.... Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering..... Previous owner installed a new cell when I took possesion and labelled install dates on the cells... #1 - 2/07 - s/n 60844871 #2 - 12/07 - s/n 71120735 #3 - 2/07 - s/n 60844872 ------------------- When I pull up System Monitor (from the secondary) I see the following: .22 9.7 .22 12.7 .20 8.7 Unit was calibrated a bit over a week ago over at Padipro's... Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...? Should I recaibrate and pull values again...? Training is the end of next month; how many spares should I have on hand... -Tim
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17th December 2007, 20:42	#2 (permalink)
JonnyB Jonny The Hatch Current Rebreather/s: MK 15.X Titan Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Megalodon Sport Kiss Classic Kiss Other CCR Other SCR Home Build Join Date: Jan 2005 Location: Sweden (Stockholm)/Cyprus(Ayia Napa) Posts: 944	Re: Cells.... I would flus the unit in 100% O2 and et the new mv. Take the mv from air calibration and multiply by 4.7 to see if it is somewhat linear. If it is linear you do not need to recalibrate. /Jonny Quote: (Originally Posted by netmage) Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering..... Previous owner installed a new cell when I took possesion and labelled install dates on the cells... #1 - 2/07 - s/n 60844871 #2 - 12/07 - s/n 71120735 #3 - 2/07 - s/n 60844872 ------------------- When I pull up System Monitor (from the secondary) I see the following: .22 9.7 .22 12.7 .20 8.7 Unit was calibrated a bit over a week ago over at Padipro's... Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...? Should I recaibrate and pull values again...? Training is the end of next month; how many spares should I have on hand... -Tim __________________ A quote from Crazyduck - In remembering our own Rob Davies. "Outbound flight 777 heavy you are cleared for flight Due west into that warm red Texas sunset You have angels on your wings and divers memories on your six." Rest In Peace http://www.divetekcyprus.com http://www.diveccr.com
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17th December 2007, 20:42	#3 (permalink)
Janos "Two Sheds" Current Rebreather/s: Classic Kiss Other Rebreather/s: Classic Kiss Join Date: Feb 2005 Location: East Surrey Posts: 580	Re: Cells.... Quote: (Originally Posted by netmage) Was reading through the manual and came across the bit about cell ranges being from 0.8 to 1.3 mV and decided to do some tinkering..... Previous owner installed a new cell when I took possesion and labelled install dates on the cells... #1 - 2/07 - s/n 60844871 #2 - 12/07 - s/n 71120735 #3 - 2/07 - s/n 60844872 ------------------- When I pull up System Monitor (from the secondary) I see the following: .22 9.7 .22 12.7 .20 8.7 Unit was calibrated a bit over a week ago over at Padipro's... Is this low mV output and inconsistency in relation to the other cells an indication that that third cell is on its last legs...? Should I recaibrate and pull values again...? Training is the end of next month; how many spares should I have on hand... -Tim If it's in range don't worry about it. Each cell has a different voltage. You could have three cells at 9mV, or three at 12mV, or a mixture of both and somewhere in between. Don't worry about it. Janos __________________ You can lead a horse to water but you can't climb a ladder with a large bell in both hands - Vic Reeves www.hellfins.com/shed
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17th December 2007, 21:24	#4 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 761	Re: Cells.... Quote: (Originally Posted by JonnyB) I would flus the unit in 100% O2 and et the new mv. Take the mv from air calibration and multiply by 4.7 to see if it is somewhat linear. If it is linear you do not need to recalibrate. /Jonny Or to be a little more exact, take mV(air) x (O2 purity)/0.209= mV O2 If the actual mV O2 is higher thanthe calculation, then Bob's your uncle. If it is consistently less, and you're unable to get to 1.6 or so @ 6m, then Bob's your aunt, and you want to do something about it. Given your air mV are above 8mV, and your within .19-.23 in air, I'd have a good first impression. Currently grounded (again) for no cells . Life in the tropics can be a PITA. __________________ Gilles http://www.dirrebreather.com
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18th December 2007, 00:29	#5 (permalink)
*ScubaDadMiami* Moderator Current Rebreather/s: Optima Other Rebreather/s: Join Date: Sep 2005 Location: Florida, USA Posts: 1,937	Re: Cells.... You will frequently find variations in cell MV. This will be the case even from cells that are coming from a new batch. If you can get a calibration and then close to 1.6 PO2 on a 20 foot flush with a reasonable response time, you should still be good to go. When you get to a year, the smart move is to change even if they are reading well still. However, you might want to consider changing one in month 11 and one in month 12 out of the two that you have there. This will lessen the chance of putting two bad cells in at the same time. BTW, as you will find, there will be a spread between cells after a while during the dive. So long as the spread is not very big, that is normal. Cells are among the weakest link in the rebreather equipment. __________________ Howard Packer IANTD CCR Instructor Miami Beach, Florida CCRDiveTraining.com
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18th December 2007, 08:20	#6 (permalink)
Mark Chase I go down for ages Current Rebreather/s: Classic Kiss Other Rebreather/s: Inspiration Classic Join Date: Jan 2005 Location: Kent Posts: 2,470	Re: Cells.... I got all keen and mapped the Mv output of my cells for a while (I dont bother now). I found they started out low then got higher and higher as they got older. My hammer head would often reject new cells. I soaked the cell in 02 over night then i managed to get it working in the HH next day. I do this all the time now with new cells. I leave them in a bag of 02 for 24hours before I install them. I have a cell from 2005 thats still chucking out 12mv and works fine. I only use it for testing stuff and its on the bench in between use not stored in a bag. It did 12months in my CCR first. I had some cells that wouldn't calibrate in the HH even after a soak. The MV output was too low. These cells failed very quickly. One was found to be current limited on the first dive. Martin Parker said it was the Hammer Heads fault and there was nothing wrong with the cell. This was rubbish because I got the same output readings on the Classic head. ATB Mark Chase __________________ Is it supposed to make that noise ? I took my unit to the dive shop and demanded they bolt on every thing that would fit. Join my elite diving teem and get a Tshirt "Doing It Chasey"Hammerhead Eccr Advanced Diving System
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18th December 2007, 13:21	#7 (permalink)
netmage Hello Kitty...... Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2005 Location: Coconut Creek, FL Posts: 352	Re: Cells.... Ok, so a few PM's talking about cell checkers and linear testing had a little light bulb go off this morning... I havn't quite decided if it's halogen, led or 35W HID.... or a flooded scout.. These cell checkers are basically a pressure pot right? A chamber that can be pressurized, flooded w/ O2 and milivolt's read off the cells...? The expensive 'guts' are already in the meg itself... Why not something like caps that threads on, tap one for a valve and quick disconnect for O2 feed and the other for an IP guage....? Maybe a bleed valve to vent the original air from the chamber.... I'd have to imagine +.6 ata wouldn't hurt the unit... -Tim Last edited by netmage : 18th December 2007 at 13:57. Reason: corrected math
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18th December 2007, 13:42	#8 (permalink)
JonnyB Jonny The Hatch Current Rebreather/s: MK 15.X Titan Other CCR Other SCR Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Megalodon Sport Kiss Classic Kiss Other CCR Other SCR Home Build Join Date: Jan 2005 Location: Sweden (Stockholm)/Cyprus(Ayia Napa) Posts: 944	Re: Cells.... Quote: (Originally Posted by netmage) I'd have to imagine +3 ata wouldn't hurt the unit... Dont say that! I recal a certain incident... /Jonny __________________ A quote from Crazyduck - In remembering our own Rob Davies. "Outbound flight 777 heavy you are cleared for flight Due west into that warm red Texas sunset You have angels on your wings and divers memories on your six." Rest In Peace http://www.divetekcyprus.com http://www.diveccr.com
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18th December 2007, 13:47	#9 (permalink)
O.C.Diver Helium Addict Current Rebreather/s: Classic Kiss Other CCR Home Build Other Rebreather/s: Not Bought Yet Other CCR Home Build Join Date: Mar 2006 Location: Salisbury MD USA Summers; Wandering Florida Winters Posts: 213	Re: Cells.... Quote: (Originally Posted by netmage) Ok, so a few PM's talking about cell checkers and linear testing had a little light bulb go off this morning... I havn't quite decided if it's halogen, led or 35W HID.... or a flooded scout.. These cell checkers are basically a pressure pot right? A chamber that can be pressurized, flooded w/ O2 and milivolt's read off the cells...? The expensive 'guts' are already in the meg itself... Why not something like caps that threads on, tap one for a valve and quick disconnect for O2 feed and the other for an IP guage....? Maybe a bleed valve to vent the original air from the chamber.... I'd have to imagine +3 ata wouldn't hurt the unit... -Tim If I'm reading you right. A 6" diameter scrubber will have about 28 square inch surface area. Putting a 2 ata positive pressure in the scrubber can will yield 29.4 psi of pressure. There will be 830 pounds of force trying to blow the lid off your scrubber. Sounds like latch failures and a posthumous Darwin award. Ted __________________ Consider this my opinion.......sometimes I'm even right, but remember.........YMMV. Ted Green Charter Boat "OC Diver" http://www.ocdiver.com
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18th December 2007, 13:50	#10 (permalink)
netmage Hello Kitty...... Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Dec 2005 Location: Coconut Creek, FL Posts: 352	Re: Cells.... Quote: (Originally Posted by JonnyB) Dont say that! I recal a certain incident... /Jonny Got a link? I got overzealous in my math 3ata would be 60'..., so... 1.6 ata would be 20'
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