Re: A couple of questions (picture)

[Subscuba@aol.com]

Hello Sean,

Thank you for sending the pictures of your Sub. AOL sends them as a mime (?)
file and I cannot look at them at this time. I am planning to get a scanner
this weekend and hope to look at them then. It may be useful to send them to
Ray, who could post them to the website as he did with my wet sub.

Incidentally, I saw in the February 1998 issue of "Scuba Times" on page 12
that Farallon is planning to bring out a DPV without batteries having a
cruising range of 12 to 15 miles at a speed of 6 knots. I would like to know
what technology they intend to use for their energy source, fuel cell???
Anybody know? Marketing Hype?

To answer your questions:

1) I do recommend the AGM batteries, they require no special venting. I would
not charge them in your pod without ventilation. It is a concern that these
batteries are in the same compartment that your breathing air comes from. What
happens if the pod floods at depth? Probably the batteries would be the least
of the problems.

2) The hydrogen problem. I do not always believe vendors claims, although this
technology in smaller scale has been in use for at least 1 decade. The problem
I am worrying about is the valve used in the battery. If the battery is ever
subject to abuse, such as reverse charging under excessive depth of discharge,
severe overcharging or even a momentary short, the valve can open under the
increased pressure. Once this happens, it releases gasses and entrained acid
into the battery compartment. Then does the valve seal again with the same
integrity? One vendor's Ni-Cads had an overpressure valve which consisted of a
sharp point which punched a hole in the battery similar to the old style beer
can opener. The cell then continued to operate but released gasses and dried
out. This would occur just once to slowly destroy the battery. Other vendors
used resealable valves. This causes a crediability problem for me and explains
the conservative statement "maybe". If this were my sub I would go ahead and
use the AGM batteries. Just bear in mind that nothing is risk free.

3) I require 3 each 12 volt group 27 batteries for my Sub. This gives me a 36
volt source to operate my 24 volt trolling motor controlled by the motor
electronics.

I am glad you are confident that my batteries will be safe to use. I am not
happy with putting this much energy between my legs but who wants to live
forever? Sorry about the comment about copying messages back to the sender. I
sent a message and file to somebody. He sent it back with the same file and
message attached and took 6 minutes to download. His message was, "I agree."

 I agree that the extra expense for the better batteries is worth it.

I wish I could see the pictures. I don't have the nerve to go for a dry Sub
yet. Perhaps after the wet Sub and I get a little older.

Have fun, I wish you sucess on your Sub. Looking forward to seeing the
pictures.

Ken