Re: I got an idea, Lets talk about subs now.

[Subscuba@aol.com]

Hello Alec,

About drilling a hole in a sealed lead acid using AGM plate construction.

If you read the literature about the potential solutions to battery problems 
there doesn't seem to be any really good solution.

If you drill a hole in the sealed AGM battery you can have the following 
problems.

1) If directly vented to the atmosphere then the water as part of the 
electrolyte will evaporate and concentrate the remaining sulfuric acid 
degrading the battery and reducing the battery capacity. Read this as 
destroying the cell.

2) If not vented by a hole in the battery then why the hole? If you want the 
hole as part of the pressure compensating system then you vent the battery 
with the same result as in 1).

3) The recombination reaction in the battery during overcharge depends on 
building up a certain internal pressure and recombining the decomposition 
products, primarily the oxygen, I think. The battery plate materials and 
quantity also determine which plate charges first and which plates have the 
recombination reaction occurring. If you interfere with this process the 
battery will lose electrolyte by decomposition or water loss. Same result as 
1).

On the subject of the GEL CELL it is my understanding that the electrolyte is 
immobilized by the use of a silicon dioxide material which cakes the 
electrolyte. The cake integers with the mobility of the charge carriers and 
degrades battery performance. The cake is also subject to cracking under 
shock and vibration. I suspect if you put oil into the cells the oil would 
still wet the plates and severely degrade the battery.

If you drill holes in each cell of the battery you can indeed achieve better 
pressure compensation but at the cost of battery degradation and potential 
explosive gas release into your battery compartment.

Bottom line, I don't recommend it! Depending on your finances it would still 
be interesting to try drilling a hole in the cells. I wouldn't try it on my 
batteries.

The best I can think of is to use sealed AGM batteries in a sealed 1 atm 
compartment like the Perry Shark Hunter. Also use catalaytors and ventilate 
during charging and don't discharge the batteries to more than 50% depth of 
discharge.

Good luck,

Ken Martindale