Re: Lifeline GPL-27 Batteries

[Subscuba <Subscuba@aol.com>]

Mike Kimble, President
Lifeline Distributors Inc.

I appreciate the cost savings you allowed me, Thank you.

It's nice to know you have diving experience and are familar with water
pressure. This message is to give you a better idea of my application as we
discussed on the phone.

My Sub is a one man wet Sub about 10 feet long 28.5 inches in diameter powered
by a Minnkota 70 pound thrust motor, somewhat similar to the swimmer delivery
vehicles (SDV) you are familar with but much lower in the state of the art and
cost, I hope. I designed the PWM electronics that drives the 24 volt motor
from three 12 volt Lifeline GPL-27 batteries. Battery drain is about 30
amperes at full speed. Calculated speed is a little over 5 knots. Sea trials
maybe within two months.

The batteries are contained in an aluminum battery box sealed from the water.
This air chamber also contains my electronics and motor. The motor seals are
only good for about 30 feet of water so pressure compensation is used for the
air spaces. The maximum differential pressure between the outside ambient and
the air chamber will be less than 2 to 4 psi. Depending on the orientation of
the Sub this differential pressure will be positive such that a leak will pass
air out of the spaces not water into the air chamber. The air chamber is not
one enclosure but four being the battery box, the electronics housing, the
motor internal air filled spaces and the instrument panel. Connections between
the enclosures are made with 1 inch hose containing the necessary wiring.
Terminations to the enclosures are made with hose barbs and hose clamps. The
batteries are the lowest part of the enclosures such that with normal
orientation of the Sub any potential water leakage will settle in the low part
of the battery box. The instrument panel located in the front of the Sub
contains the control and monitoring electronics which includes a leak detector
from the battery box. The design depth is 200 feet with a 2 to 1 safety margin
determined largely by the strength of the flotation materials (homemade
syntactic foam) and the battery limitations.

Thus the batteries are exposed to a pressure external to the battery case of a
maximum of 4 atmospheres (air at a depth of 130 feet) relative to the internal
1 atm contained in the battery case. I intend to limit the dives to no more
than 130 feeet, at least initially.

The process of the pressure compensation actually ventilates the air spaces
both at descent and ascent. At descent air is let into the air chamber and at
ascent the air is released. I have a friend that did this with flooded cells
and catalytor caps. They have been using this system for about 8 years with no
battery problems, lots of other problems though. I do not want to use flooded
cells since the question of operation in the inverted position invites acid
release among other things. The VRSLA system is superior. I will charge the
batteries with the battery box open and ventilated to assure starting the
dives with fresh air in the air chamber.

I hope this provides more details from our phone conversation. I'm looking
forward to receiving the batteries. I have also sent a copy of this message to
the PSUBS group I suscribe to, they should have an interest in the batteries.
Lifeline's website is at " http://www.dcbattery.com/lifeline2.html ". The
PSUBS website is at "http://www.psubs.org/index.html". 

Thank you,

Ken Martindale
2315 Weber Road
Malabar, FL 32950
407-723-1176
Subscuba@aol.com