Sensor life, replacement?

firemandiver

I have a couple of questions regarding RD22 sensors. I'm sure there are folks who have been is this situation before, so I wanted to ask the site.

Supposedly they're good for up to 3 years in air. Mine have depleted to 20% in about 11 months. I realize that three years is a bit much to hope for, but I was hoping to get more than a year out of them. If I dove hundreds of dives a year I would expect them to expire quickly, but I work too much and don't get to dive as often as I wish. I only have six days of diving, or about 18-20 dives on them. I store my Oxy2 in a Pelican case when not in use, so I would think that should help prolong the sensor life. Perhaps the sealed case is actually causing them to deplete faster. Any ideas, suggestions?

My second question is about changing them. As a safety precaution I have always changed my sensors and battery when they get to 20%. I have never pushed the limit to run them close to or all the way down. I may be tossing them prematurely, and wasting good sensor life and money. Of course I don't want to let them go to 2% and then have them crap out on a dive, but I don't want to be wasteful either. Is my 20% rule a good idea? If not, what do some of the others go by?

Third question is about the sensors themselves. My first Oxy2 was purchased new, as old dealer stock, with the factory sensors still in the potted meat cans. Before I ever opened the sensors I picked up another used Oxy2 with about 40% sensor life. I put the new one up for a rainy day and have been diving the 2nd hand unit. I did however swipe the sensors from the new unit the first time the used unit needed a sensor change. One was totally dead, and the other showed 35% upon installation, even though they were still in sealed cans. I figured they were just old and had gone bad frrom sitting for several years. I ordered new cells from Oxycheq, and they had a manfacture date of the prior week, so they were as fresh as they get. These are the cells that have petered out in less than a year. Sorry for the lenghty preamble, but I wanted to provide as much info as possible for my question. Is there a major difference between sensor brands? Is one particularly better than the other? Any suggestions?

Thanks for the help.

FD;)

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"There Is No Try........Do...... or Do Not" Yoda

Bosh

I have replaced twice. Both times i used Buddy sensors.
From various threads here i understand they are one of the few companies that test the sensors before shipping.
For me a good reason to buy them.

The first couple lasted 18 months and were then on 5% or so.

The next pair is still in and only a few months old.

Slightly off topic: The battery in the wristunit dies around 50 %. Mine at 48%, 5 minutes into a dive to 40m/130 feet and a planned runtime of an hour .

Time to test the bailout :D

Best regards

Bo

Tienuts

Kevin Juergensen said it best....something like this:

"Cells stored in air will last 1 year.
Cells stored in pure o2 will last 12 months.
Cells stored in a sealed container of N2 will last 52 weeks.
Cells stored in a lead-lined temperature controlled vacuum vessel on the moon will last 365 days. "

Change them after a year. Your life is worth more than the cost of a cell.

Moisture will mess with a sensor big time. If the pelican case you are storing them in has any kind of moisture, it will affect them. I would just keep them in the open air, in a cool benign environment. Impact, heat and moisture are the killers of cells.

People will jump in this thread any second and yell "AII cells suck." Other will chime in with their horrible Teledyne experiences and how they suck. We sell both and the simple fact is, all cells suck. They are unreliable little bastards. I keep stats on the failure rates of both, and on average, they are both the same.

Outlaw

so, what's the opinion of the community on this.

1. better to let the cells dry before packing them after a dive? if yes, how long to dry? in open air or spray them slowly? OR

2. just pack them as they are in their box/cover etc?

P,S sorry for jumping into this, just wanted to clarify this once and for all...

Spyros

Tienuts

Heat and impact seem to permanently damage cells. Moisture seems to affect cells on a short-term basis.

On a dive trip, I don't think it matters when you dry them, as long as they dry out before the next use. The amount of drying time? I guess that depends on usage and how much moisture they are exposed to over a period of time.

So if you can't let them air-out prior to packing your gear, dry them out when you get home.

Jill Heinerth has a theory that you'll get more long-term life by letting them dry out over several days, and she keeps 2 sets of cells in a weekly rotation.

Some cells seem to be more resistant than others to moisture.

wedivebc

Does anyone know how the Oxy 2 determines when the cells are at 20% expected life? Seems to me a cell works until it doesn't. Thats why we change them annually.

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Cheers,

Dave....

www.wedivebc.com

kwinter

I would be thrilled to get a year. I have been through 5 AI cells in the past 8 months. They have lasted anywhere from 3-7 months. I just put in my first Teledyne and will see how long that lasts. It's not exactly comforting to know you've been keeping stats on both brands and that they both stink.

I didn't know you sold both. I thought all cells that had a DRE label on them were AII. How would I order Teledynes?

Ken

firemandiver

Thanks for the input so far. I've never put any gear up wet. Well, once a long time ago, but that's another story. It sits in my garage usually for at least a week drying before I pack it away, so that's not an issue. Heat...maybe, but not real likely. I store all my gear, with the exception of computers, in a small shed on the back of my shop. It's totally dry and moisture free, but not air conditionded. It can get pretty warm in the summer, but not sauna like. Still I guess I really should move the Oxy2 inside with the other electronics.

I've read some other posts regarding sensors, and the general consensus seemed to be about a year of sensor life was the norm. It makes sense, and I agree it's not worth risking your safety, just wondering how some get 2-3 times the sensor life as I do. On the flip side I guess I should be thankful....some have to change sensors several times a year!

My LDS keeps his Oxy2 in a cardboard box on a shelf in the shop. He has been on the Dolphin since it first came out, and only changes his about every 2.5 - 3 years. Four sensor changes in 11 years is pretty good. Maybe it's the cardboard box......gotta get me one of those!:D He was getting his sensors through Aqualung, and they were the ones in the little cans from Uwatec. He still had a few left in stock but they were way out of date. He has been using them because it's what he had on hand and they seem to be just fine, even though the date on the can said they were expired. Since Drager pulled the plug in the US he is no longer a dealer and hasn't ordered any more sensors. That's why I found them on my own at Oxycheq.

What about the 20% sensor change? Overkill, or good idea?

Thanks, FD.

__________________
"There Is No Try........Do...... or Do Not" Yoda

firemandiver

Does anyone know how the Oxy 2 determines when the cells are at 20% expected life? Seems to me a cell works until it doesn't. Thats why we change them annually.
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The unit prompts you when the cells are installed if they are new or old cells. If you input that they are old cells, it uses the last stored value. If you tell it they are new cells, it resets the unit to 100% and the countdown starts over. I suspect it measures the resistance through the sensor at "new" and uses that as a starting point.

FD;)

__________________
"There Is No Try........Do...... or Do Not" Yoda

Bosh

To be honest: I dont have a clue. But my guess is it has a calender.

When the sensors are disconnected, and then reconnected the Oxy2 asks whether its new or old sensors.
You choose, and the Oxy2 remembers the old % or starts at 100.

best regards

Bo