Re: [PSUBS-MAILIST] Lead-Acid Oil-Filled Batteries and Catalysts

[Phil Nuytten <pnuytten@compuserve.com>]

To Vance-Readers re oil-filleds and comped pods:
        As seems to be often the case, Vance is right on both counts re air
comp and oil filled batteries. Obviously, if you have a rigid,
pressure-proof container capable of withstanding the 2 X the safe working
depth by design calculation - then you don't need to oil-fill it. All you
need to do is to make sure it is fully vented during charge ( by removing
the end cap(s) and sticking a 3" or 4" blower hose inside the pod.
Additionally, you need a low cracking pressure non-return vent ( usually
.25 psi) to take care of the small amount of overpressure that is generated
on discharge. If your pod cap(s) are piston or radial o-ring sealing, you
will hear and feel a small 'flumph' from the quarter pound pressure diff on
removal ( if you hear 'voom', and you wind up on your back with the cap
clutched against your belly, the vent valve cracking pressure is set too
high!). Those faint of heart often provide a small needle valve in the cap
to vent before removal for charging.
        Oil-filled batteries need a flexible oil compensation reservoir.
This can be a separate unit or a flexible membrane area on the rigid
portion of the battery tray/box. Pressure-wise, you don't need a rigid
portion. You could stick your batteries in a rubber sack, fill it with oil
and tie the end in a knot. Hard to mount, though.Get a 'Bello-fram' catalog
and you will see that they make a swillion different types of closed
one-end, flange-the-other, with corrugations in-between, nylon-reinforced,
neoprene molded  caps.  . .(or smooth sides are OK, also - the oil comp
unit doesn't care how ungracefully it collapses). Or just make the top of
your battery box one giant flexible solid ( not foam neoprenr)neoprene
diaphragm. It will have sufficient give to pouch slightly and  allow any
gas generated during discharge to form a bubble or bubbles at the top of
the tray. You need a substantial vent valve to handle the gas during charge
and vent it harmlessly away. On 'Deep Rover' we use battery pods that are
long rectangulat boxes made of UHMW or rigid PVC one inch thick. We put 10
X 12 VDC Deep Cycle batteries in the tray, put a quarter inch thick
neoprene or polyurethane sheet over top - drilled with holes for many
1/4-20 SS bolts which go through an anodized aluminum right-angle retainer
flange, through the top diaphragm sheet and into SS heli-coil inserts in
the 1" tray walls. Install a vent valve in the top of the diaphragm of at
least half inch throat size - quarter-turn is fine - run a piece of tygon
to a capped plastic bottle that is threaded to accept a tygon tubing barb
fitting at each end. Put a baffle in the center of the bottle - 3/4's of
the way thru' the diameter ( this will capture the oil that will enevitably
come out with the vent gas) lay the bottle on its side and attach another
chunk of tygon to the other end of the oil bottle and lead it away
somewhere. This is for the vent gas. MOST IMPORTANT: Take a large fishing
'flasher' ( salt-water type) at least ten inches long and about 3 or 4
inches in width. Attach it to the end of the vent hose with about four feet
of fishing line. When you see this flasher wobbling and flashing in the sun
as you lift your sub over-board, you will realize that you forgot to close
the vent valve and remove the oil-collection bottle after charging - and
can correct before anyone spots it! 
Regards
Phil Nuytten 




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