Hi Stan.
In my system design, I am going to run flexible conduit containing the
wires from the battery pod directly to the hollow steering shaft of the
motor. I will attach the conduit to the steering shaft with a waterproof
connector. Tubing running through the steering shaft
to maintain pressure in the motor will be unnecessary since the steering
shaft itself will be connected to the battery pod via conduit and the
battery pod will be air equalized, therefore the steering shaft will act
as its own tubing since the steering shaft interior is open
to the inside of the motor housing's interior thus not only carrying the
wires from the battery pod to the motor, but also the equalized air from
the pod to the motor housing.
I will not need anything other than a scuba tank and scuba regulator to
equalize my system. On descent, the scuba regulator will sense the
increase in pressure (via its purge valve) and open that valve and allow
air into the battery pod which is joined via the conduit
to the motor's hollow steering shaft and will pressurize both the battery
pod and motor at the same time. When the inside pressure is equal to the
outside pressure the scuba regulator's purge valve will automatically
close and stop venting air into the battery pod and motor.
On accent, the air exhaust valve on the scuba regulator will allow
expanding air from the motor and battery pod to exhaust out of the scuba
regulator. Simple yet effective.
I don't need any other check valves nor tubes. As to hydrogen explosion
concerns I will be using a hydrolator and hydrocaps. See the article below
on hydrocaps.
Kindest Regards,
Bill Akins.
Home Power tests the Hydrocaps
One of the perpetual chores in home power systems is watering the
batteries. These large lead-acid cells always seem thirsty for distilled
water. As these batteries recharge, some of their water escapes.
Periodic watering of these large cells is essential for battery survival.
Failure to do so results in the early demise of these expensive batteries.
Hydrocaps are devices which greatly reduce the battery's water consumption
and also offer vital safety and operating features.
The Lead-Acid Recharging Process
The electrolyte in lead acid batteries is a dilute (Å25%) solution
of sulphuric acid in water. As the lead-acid cell reaches a full
state of charge, some the water in the electrolyte is broken down
into hydrogen and oxygen gasses by the recharging current. These
gasses escape from the vent on the top of each cell. This process,
called "gassing", accounts for the water lost from the cells. The
actual amount of water the cell loses during recharging depends on
several factors. High temperatures (>90¡F), high rates of recharge
(>C/20), and elevated voltage limits (>2.44 VDC per cell) all increase
the amount of gassing that occurs during the recharging process.
If all the cells in a lead-acid battery are to be totally refilled
and equalized, then a certain amount of gassing will have to take
place. It's up to us to deal with this situation. First, we must
add distilled water to the cells to make up for the water hydrolyzed
into hydrogen and oxygen. Second, we must deal with the potentially
explosive mixture of hydrogen and oxygen being vented from the cells.
Hydrocaps offer solutions to both these problems.
Hydrocaps
A Hydrocap is a catalytic gas recombiner than converts hydrogen and
oxygen gasses into pure water. A catalyst is a substance which encourages
other substances into chemical change without actually participating
in that change, sort of a chemical ambassador. The process occurring
in the Hydrocap is similar to that occurring in an automotive catalytic
converter.
The Hydrocap replaces the regular cell cap. When the cell is gassing,
the hydrogen and oxygen gasses are vented into the Hydrocap. Inside
the Hydrocap, a catalyst of platinum and other platinum group metals
recombine the gasses into pure water. This water is then dripped
back into the cell. The Hydrocap recycles the water that the cell
gives off as hydrogen and oxygen gasses. This eliminates the danger
posed by the hydrogen gas and vastly reduces watering the cells.
When the cell is gassing, some of the recharging energy is not being
stored in the cell, but is breaking down water into its constituent
elements- hydrogen and oxygen. Some of the energy used in the conversion
of water into hydrogen and oxygen is retrieved by the Hydrocap.
When the Hydrocap is operating it gets warm. This heat energy is
a by product of the catalytic recombination of the hydrogen and oxygen
back into water. While this may seem just an interesting aside,
we found the Hydrocap's warmth very useful as an indicator of the
cell's state of charge.
Testing the Hydrocap
We installed 6 Hydrocaps on two Trojan L-16W batteries (350 Ampere-hours
at 12 VDC) in the Plywood Palace on 9 March 1989. These batteries
are recharged by a motley assortment of five PV panels (Å200 peak
Watts) and our home made Mark VI engine/generator system (12 to 16
VDC from 5 to 100 Amps). See HP2, page 25, for a description of
this engine/generator system. I usually add about a pint of distilled
water to each cell per month. Each cell (and this battery has six)
has an electrolyte capacity of three quarts. We've been cycling
this battery about three times a week; this means lots of recharging
and its associated water consumption. Basically, this battery is
consuming about $8 worth of distilled water a year.
I removed the cell caps, filled the cells with water, and replaced
the stock caps with Hydrocaps. I then fired up the Mark VI
engine/generator
to recharge the battery and check out the Hydrocaps' operation.
The battery was already just about full from the PVs' daily input.
It only took a few minutes before the battery voltage rose to 14.5
VDC at 17 Amperes input (about a C/20 rate for this battery). The
battery was now gassing slightly. I raised the voltage limit on
the Mark VI to 14.8 VDC and now I could hear the cells gassing violently.
Each of the Hydrocaps was starting to get warm. I continued to recharge
the battery for a while and found that for this particular battery
the Hydrocaps stayed warm (but not hot) with a voltage limit of 14.6
VDC. I found this fascinating. For the very first time I had some
feedback on how much each cell was actually gassing. The more a
cell gassed, the hotter its Hydrocap became. This battery is over
9 years old and has one cell which is slightly weaker than the rest.
I've determined this by long term voltage measurement of the individual
cells during all sorts of charge/discharge rates. Sure enuff, the
Hydrocap on that particular cell was the slowest to warm up.
The heat output of each Hydrocap provides three valuable bits of
battery information. One, it allows the user to accurately determine
the voltage at which his battery gasses (a good voltage setpoint
for regulators). Two, it allows early detection (and correction
via equalizing) of a weak cell by its relatively cooler Hydrocap.
Three, when all the Hydrocaps reach the same temperature, then all
the cells are equalized (at the same state of charge). And accessing
this information is low tech, just feel the temperature of the Hydrocaps!
It's now been over two months since the Hydrocaps were installed
on our L-16Ws. I checked the water before writing this and all of
the cells are still full. I have not added a drop of water to the
battery during this test period. Operation without the Hydrocaps
would have consumed about 1.5 gallons of distilled water during this
interval. I assume that I will have to eventually add some water
to the battery, even with the Hydrocaps. From the virtually zero
decrease in electrolyte level to date, I think that yearly watering
of the cells is possible in well proportioned systems. Every time
we open a battery's cell to add water we risk contamination of that
cell. Batteries are chemical machines and depend on the purity of
their reactants for longevity. Hydrocaps reduce the frequency of
required water addition and thereby lessen the possibility of cell
contamination.
The top surfaces of our batteries are staying cleaner. During recharging
without Hydrocaps, a fine mist of acid electrolyte is expelled from
the cells along with the hydrogen and oxygen gasses. With the Hydrocaps,
there is actually a negative pressure within the cap. The gas
recombination
creates a slight vacuum within the Hydrocap, and the acid mist is
washed back down into the cell by the recombined water. Slick.
The process keeps the acid electrolyte from reaching the top of the
battery's case and corroding everything. Cleaning the tops of our
batteries is one of my least favorite chores. My nose always itches
when I've got acid on my fingersÉ
Based on a catalytic reaction, the Hydrocaps last a long time. The
manufacturer says, and I quote, "The life expectancy of a Hydrocap
is more than 5 years with overcharge rates below 3 Amperes for two
hours each day." What this means to those of us using PVs as energy
sources in properly proportioned systems, is very long lifetimes.
If our power sources aren't grossly overcharging our batteries, then
a set of Hydrocaps should last between ten and twenty years. Sizing
Hydrocaps
Since different batteries have different cap sizes and styles, the
Hydrocaps must be fitted for a particular battery. The manufacturer
aided us, as he does all his customers, in selecting the right size,
shape and overcharge rate for our battery system. Fortunately, Hydrocap
makes a specific model that will fit most any battery and situation.
Hydrocap Cost
The manufacturer sells Hydrocaps directly to the end user for $5.50
each, delivered, in quantities of six or more. I figure that over
the lifetime of a set of Hydrocaps I'll spend at least two times
their purchase price on distilled water alone. And this doesn't
include my time to refill and cleanup the batteries, or the added
safety factor of greatly reduced explosive hydrogen surrounding the
batteries during recharging, or the interesting and useful information
offered the the cap's heat. The Hydrocaps are worth at least what
they cost.
Hydrocap Access
Contact Mr. George Peroni at Hydrocap Corp., 975 N.W. 95 Street,
Miami, FL 33150 ¥ telephone: 305-696-2504. George not only sized
our Hydrocaps, but was very helpful in providing technical information
about his product. Conclusion
Hydrocaps are a must for lead-acid battery users. They increase
the safety of the battery area by reducing explosive hydrogen gas.
They are cost-effective by their savings in distilled water alone.
They reduce battery maintenance while increasing battery longevity
and reliability. They also offer direct tactile feedback regarding
the state of charge of the battery's individual cells. We're now
running Hydrocaps on all our cells and are specifying them on all
the batteries that Electron Connection Ltd. installs. Hydrocaps
should be considered necessary, basic equipment for any system using
lead-acid batteries. RP