Rebreather World - View Single Post

n2diving · 2nd May 2007, 14:28

Quote: (Originally Posted by jcolley)

If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use.

The answer I had from one of the experts regarding the effects of storage in inert gas was a definate 'not sure'. The cells are manufactured and sealed in ordinary air in a somewhat gas permeable bag... the cell will deplete most but not all of the oxygen in the bag. As many here can attest, the cell can and does degrade in an unopened bag and the vendors say that the shelf life is two years. Thus there are several factors at work determining the life of the cell, not just the exposure to oxygen.

If you were to store them in inert gas, what would happen? As mentioned earlier, storage in inert gas would introduce issue of the 'wake up' time on the cell and if the inert gas is other than nitrogen what effect does this have? Certainly some aging processes would continue even in inert gas, but if some components age differently than others on a cell previous exposed to oxygen how does it affect the cell behavior or performance? Another concern mentioned is that pure inert gas contains no moisture, would this have a dessicating affect on the cells? The expert I talked to was most concerned about drying of the electrolyte. Since no testing has been performed to answer these questions, it seems like best practice not to store your sensors in inert gas.

The recommended way to get the 'best' performance from your sensors: store them at cool room temperatures in ordinary air.... this was what they were designed for.

I had not considered the mechanical stresses of unneccessary removal/replacement of cells. But one broken wire in a harness requiring a replacement is going to cost more money than you might have saved from trying to extend the life of the cell.

2nd May 2007, 14:28	#7 (permalink)
n2diving RBW Member Join Date: Feb 2005 Location: Florida, USA Posts: 320	Re: Preserving cell life? Quote: (Originally Posted by jcolley) If a cell continues to degrade as a result of reaction with oxygen, then it would make sense not to expose it to oxygen when not int use. The answer I had from one of the experts regarding the effects of storage in inert gas was a definate 'not sure'. The cells are manufactured and sealed in ordinary air in a somewhat gas permeable bag... the cell will deplete most but not all of the oxygen in the bag. As many here can attest, the cell can and does degrade in an unopened bag and the vendors say that the shelf life is two years. Thus there are several factors at work determining the life of the cell, not just the exposure to oxygen. If you were to store them in inert gas, what would happen? As mentioned earlier, storage in inert gas would introduce issue of the 'wake up' time on the cell and if the inert gas is other than nitrogen what effect does this have? Certainly some aging processes would continue even in inert gas, but if some components age differently than others on a cell previous exposed to oxygen how does it affect the cell behavior or performance? Another concern mentioned is that pure inert gas contains no moisture, would this have a dessicating affect on the cells? The expert I talked to was most concerned about drying of the electrolyte. Since no testing has been performed to answer these questions, it seems like best practice not to store your sensors in inert gas. The recommended way to get the 'best' performance from your sensors: store them at cool room temperatures in ordinary air.... this was what they were designed for. I had not considered the mechanical stresses of unneccessary removal/replacement of cells. But one broken wire in a harness requiring a replacement is going to cost more money than you might have saved from trying to extend the life of the cell.
(Offline)