Batteries and fans.

[shawl@torchlake.com (Jonathan Shawl)]

Thanks for the advice Vance.
I thought I would answer this one to the group so all can benefit from it. I have
already thought about the dangers with batteries going BOOM and I have learned my
lesson. I have seen it happen about 3 times in my life, but never in my sub. One
was a car battery that had a internal flaw and just blew up wile being charged,
It sounded like a shot gun, good thing no one was around it. Another was a phone
co. battery set that had a faulty (broken) cap and when the guy working near the
batteries miss connected a big cable, Sparks flew then BANG, (more than one) when
that one cell blew up it cracked and then blew up several surrounding cells,
chain reaction real fast! The worst part was trying to stop gallons of acid from
spreading too far, then the clean up, not easy! And the 3rd time was my fault. I
hooked up a load using jumper cables, to a set of freshly charged golf cart
batteries. Oops! I knew better than to do that, but it was outside, out in the
open and I didn't think it would happen.  I got a acid shower. Good thing I ware
glasses and the water shower was about 20 seconds away or it could have been
worse. Even then I could start to feel the burning on my neck. The morel of the
story, keep sparks far away from batteries no matter what. Especially when
charging or freshly charged ones. I already have plans to make separate external
battery pods before I put her back into service. I noticed you said to the group
"that AC fans make sparks too".  I never said what kind of fan I use. And as far
as AC fans sparking, that would be true if it had a start switch and start
winding like on some older belt drive furnace fans. Most all small AC fans and
many newer multi speed furnace fans that I have used are repulsion induction
types, no start winding or start switch to spark. For the record, when I do use a
fan, it is a solid state controlled, brushless 12 VDC, computer type fan, mounted
so as to blow fresh air down into one side of the open hatch and connected to a
external power supply. Your flex hose idea sounds like the best, keep the fan out
of the sub and blow air into the hull. Every 12 volt bilge blower motor I have
ever seen or used has brushes and they do spark for sure. In that case you are
depending on the air tight motor housing to ward of the BIG BANG.
On another battery story, I seem to remember that one of Cousteau's subs that had
external oil filled battery box that had a Oops when a battery terminal shorted
out on the lid during a decent and burnt a hole in it. Then the oil leaked out
and salt water got in making them too heavy and powerless. I have a Video tape
about in someplace. It just shows that most anything can happen, even to the some
of the best equipped and trained. How many thought a small spark could sink a
sub, or worse ???
Take care all P-subbers.
Jon Shawl

VBra676539@aol.com wrote:

> Jon,
>         Beware the bubble measurement.  Hydrogen off-gassing is the molecular
> breakdown of H2O and is going on very busily indeed, especially during the
> final stages of a charge.  Rather than a regular fan, I would suggest using
> one of the commercially available bilge blowers (look for those "explosion
> proof" claims).  Bilge blowers are designed to transport hazardous gases, and
> would probably manage this, too.  I have double battery pods on my K350 and
> use bilge blowers with off the shelf flex hose to vent gases completely out
> of the boat.  You can also use the bilge blowers for scrubber motor/fans to
> drive air over your CO2 absorbent.  Cheap, easy to replace, and readily
> available.  Sounds too good to be true.
>         Yes, have been into the subs for many years.  I was a professional
> sub pilot all through the 70s and early 80s.  1100+ dives and going on 4000+
> hours submerged in 9 different subs.  It sounds like a lot thinking back on
> it, and kind of pretentious, but that was a long time ago and seems to have
> gone pretty quickly from my current vantage point.
>         I like what I can see of your boat.  Be careful with those batts,
> though.  I've seen a couple of spectacular uh-ohs with bigger banks and can
> recommend against it.  Be aware also that batteries tend to off-gas for some
> time after the charge cycle ends.       If you have questions, I'll try to
> answer them.  I have some good books with information on this kind of stuff
> so might be able to dig out a kernel of helpful information for you from time
> to time.
> Happy psubbing!
> Vance