Wednesday, January 7, 2009

Rebreather Cells - the Saga Continues

Welcome back and I hope everyone had a fantabulous new year! We had a brill time...and learnt that snorkels are CRITICAL gear. Yes, we found the wading depth of my Ford F250...and then spent a fascinating 1.5hrs finding out where the water went and how to get it out! With beer, a stunning river view, hippos and thankfully no lions. But back to diving :). Gerhard has this to say:
I have had a few comments after a recent article published in a local diving magazine in regards to the "rolling" of cells for re-breathers.
You need to understand one thing. In my opinion if the manufacturer recommends something then it might be a good idea to follow the recomendation, regardless what your own opinion on the matter may be. If for no other reason than the fact that they built the unit and therefore know a whole lot more about it than any diver could (no matter how many hours have been spent on the machine).

Rolling (of the cells) is an old concept that tech divers have been implementing not only with cells but with other bits of gear as well. Back before equipment was reliable (ok, so that statement may still stand the test of time) we used to "roll" everything from flashlights to batteries.

For example , I dived a backup light from 2 different brands, the batteries were from different manufacturers and were changed prior to any hectic dive or after any dive if they were found switched on or if used simply because reliability on these items was questionable. Reliability is the very reason I do not use re-chargeable batteries in my re-breather controllers - they have a different voltage curve and you can get into trouble. Instead i use alkaline or lithium type batteries.

Interestingly enough we teach our students to roll their controller batteries but yet advocate not to roll the most questionable part on the unit - namely the cells ?!? Sheesh. If the batch has a fault you just shot yourself in the foot and yes there have been some batch issues. You never know how that cell was stored up to the day you got it. It is considered to be the most unreliable part of your unit and also the most important one in regards to staying alive.

To my knowledge the following manufacturers advocate very publicly and loudly that you roll your cells:
- Juergens Marine (Hammerhead), Dive Rite, AP Valves (Inspiration) as well as Megladon.

The choice is yours. Get cell validation or get true voting logic but the only way to achieve it is to roll the cells as the parameters will be different when compared to replacing all the cells all at once ...... and having what is called a "false positive" that might just make your 3 horses turn out to be 3 donkeys.

Keep safe...and keep diving :)

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