Re: bellows on batteries

[Subscuba@aol.com]

Steve,

The way the valve in a Valve Regulated Sealed Lead Acid (VRSLA) is intended 
to work is only as a last resort to relieve excess pressure. During normal 
operation the valve never operates. This is due to primarily two reasons. The 
first is that venting the cell spaces with air or even an inert gas will 
cause some evaporation of the water in the electrolyte degrading the battery.

The second is that allowing air which contains oxygen into the cell intefers 
with the plate that is supposed to recombine oxygen and degrades the plates 
ability to make the recombination reaction to occur. Then overcharging can 
cause the valve to open due to lack of the recombination reaction rate and 
capacity.

I suppose that if the bellows can withstand the necessary over pressure and 
can be filled with an inert gas and water vapor in the right quantity then 
the technique might work. It's important to recognize that the process 
requires each cell making up the battery to have its own bellows.

I still think the best is a 1 ATM battery container with catalaytors and a 
sealed AGM battery to be the best bet.

As an interesting note: The AGM batteries use the same basic technology as 
the sealed Gates lead acid about the size of a D cell. As advertised by Gates 
the cells are sealed but are not recommended to be housed in a sealed 
container. Sealed is a relative term since the Gates cells can be charged in 
an inert liquid like Flourinert and bubbles can be observed from the cells 
during charging. The gas in the bubbles is hydrogen. The only good seals I 
know of is glass metal seals which most of the Aerospace cells have.

Ken Martindale

In a message dated 7/5/99 12:05:33 AM Eastern Daylight Time, SJSVOB@aol.com 
writes:

<< <>
 
 <<Sounds interesting for the bellows, would the bellows withstand the 
 pressure 
 the recombination reactions would require?>>
 
 One large bellows connected to on/off valve, connected to multiple hoses 
 connected to holes in batteries.  You shut off the valve during charging so 
 the batteries can become pressurized.  Would that work better?  Am I 
 understanding this?
 
 Being a CS/EE I might add pressure transducers inside the hoses and the 
 bellows.  I'd have an alarm sound if the voltages on the transducers varied. 
 
 This would serve as a warning that I was descending without having opened 
the 
 valve.  Don't want the batteries to implode!  Might also have a warning 
light 
 come on if the valve was shut off.
 
 Steve
  >>