----- Original Message -----
Sent: Saturday, January 29, 2005 4:18
PM
Subject: Re: [PSUBS-MAILIST] A safety
improved, battery pod/motor, using air as a water pressure equalization
system
Hi Brian.
Thank you very much for that info on Dan Lance's
epoxy wire connectors Brian.
Do you have the link or know where I can read or
see more info on it? That sure would be great. I see what you mean. If I
sealed the ends of my wires going into the battery pod with epoxy except for
the round connector that attaches, and if somehow my epoxy got a crack in it
from stress, hydrogen could then ingress into the wire and go into the motor
housing. Having that system you spoke of would preclude that and add an extra
safety margin. Love to read more on this.
I must admit I know very little about gel or AGM
batteries, so I can't help you there. My knowledge is limited to lead
acid.
If you do use lead acid batteries you will not
want to submerge the batteries completely in oil otherwise you will
contaminate your cells with oil. Hence, you have to leave an air space at the
top of the batteries and the outside water pressure will still
act against that small amount of air and try to
ingress and or push in on the lighter material you spoke of using and possibly
implode your pod. Plus you might not want to just leave a few inches of air
over your lead acid batteries above the oil because then you might get
splash from the oil that would wave over the top of your batteries and
possibly contaminate them.
You might be able to use the oil method and
completely submerge your batteries with other types of batteries that were not lead acid, but of these types of batteries
as I said, I have no knowledge.
Some time ago I had an idea that if you used
a battery that was non lead acid and totally sealed, why not just encase that
battery and its wires completely in epoxy, and
then it would not even need a pod.
Just strap the epoxy encased battery under
the sub and then just run the wires coming out of the epoxy to the motor shaft
and seal the junction where the wires went into the shaft. Sounds plausable to
me but I don't know that much about batteries
except for lead acid. Except I DO know all the other types are a lot more
expensive than lead acid. In my epoxy encased battery idea I guess you
would build in some kind of provision for wires coming out of
the epoxy to go to your charger and waterproof
them. If someone could come up with a battery pack like this it sure
would make things easier for us wouldn't it? An epoxy encased battery pack
that contained no air. You could even use clear epoxy and actually see thru it
to the batteries slung under your sub. No outside water pressure equalization
would be necessary because their would be no air around the batteries with
them being encased in epoxy. It would be heavy but this would be ok and act as
a keel to keep you upright
and you could compensate with air bladders in the
wetsub body.
But I have never heard of anyone manufacturing
anything like this. Maybe someone out there will read this
and manufacture them. Lol. We should be so lucky.
Most of the posts I have read from various sites
showed people using transformer oil in their motors for those who used the oil
method of equalization. Some believe it or not use water with corrosion
inhibitors in it to equalize the motor housing.
But I have read nothing concerning using oil in
the battery pods.
I personally think (with what I know at this
time), that air equalization of the battery pod when using lead acid batteries
is the way to go. I am by no means an expert, but it seems so simple to just
use a pvc battery pod and air equalize it.
Well.....simple is subjective, lol, that's why I
haven't completed mine yet. But I don't think I would completely submerge lead
acid batteries in any kind of oil if I were you. And therein you still have an
air space over them to deal with and equalize.
As I have recognized and others have mentioned,
pvc is very strong and for normal scuba depths probably doesn't absolutely
need equalization anyway. But I am going to equalize mine. I think it is
better to not have the water pressure trying to get in past a
small
juncture and pressure equalizing would
basically keep any pressure off my battery pod which I think is
good.
If I find that my battery pod needs more ballast
to be either neutrally buoyant or just a little negative buoyant, (I want it a
bit weighted to act as a keel to preclude upending) then I will use
scuba weights which will be lead pellet bags which will conform around the
areas of the batteries in the pod. I could use sand but that would be kind of messy every time I wanted to pull the
batteries out to inspect them.
Kindest Regards,
Bill Akins.
----- Original Message -----
Sent: Sunday, January 30, 2005 12:23
PM
Subject: Re: [PSUBS-MAILIST] A safety
improved, battery pod/motor, using air as a water pressure equalization
system
That sounds very thorough, but on the epoxying
the end of the wires you might want to look at Dan Lance's Submersible
Penetrators presentation at the 2004 convention. It takes what you are
doing a little bit further and adds a layer of safety precaution.
There is a connection incased in the epoxy that in case of it getting pulled
out the wires simply separate leaving an epoxy seal at the
transition.
By using gel batteries can the hydrogen
gas problem be mitigated? I was planning on using gel batteries or
AGM.
I have been considering filling my whole
battery compartment with oil. As long as I make that space as minimal
as possible the actual amount of oil used will not be very great. Also
the pod for the batteries does not have to withstand the ambient
pressure so it can be made out of a lighter material and it does not
have to be cylindrical. I am planning on using mineral
oil. If the batteries need to be inspected or replaced then I would
drain out the couple of gallons of mineral oil at that point. Then
refill the space with oil upon completion of battery change
out.
Brian
----- Original Message -----
Sent: Saturday, January 29, 2005 6:58
AM
Subject: Re: [PSUBS-MAILIST] A safety
improved, battery pod/motor, using air as a water pressure equalization
system
----- Original Message -----
Sent: Thursday, January 27, 2005
1:40 AM
Subject: Re: [PSUBS-MAILIST] A
safety improved, battery pod/motor, using air as a water pressure
equalization system
Perhaps I PERCEIVED Vance's post where
it stated that I knew all the answers as him stating that I am
a "know it all". Perhaps I was wrong and that was not really what he
meant.
If I perceived an imagined wrong and spoke
out of turn accordingly, then for that I apologize to Vance and
this forum for my misunderstanding. I guess I am so very careful to
always strive to be polite to everyone
that when I perceive (wrongly or not) an
insult to me, I do get a bit sensitive. I will try and work on that and
strive to not be so thin skinned and sensitive in the future.
That being said, on to further design
discussion.
After more thought on the matter and even
though I still believe the hydrolator and hydrocaps (along with
the pressure induced intake of air and outgo of exhaust of the
battery pod/motor pressure equalization system itself) would be
sufficient to preclude any hydrogen problems, I have decided
to change one aspect of my design. By
making this change it should increase the safety factor and eliminate
any possibility of any motor sparking causing a hydrogen explosion
no matter how remote that possibility may be.
This change would simply entail installing
a "T" fitting on my scuba regulator replacing the mouthpiece so that the
air from the regulator can go into two seperate hoses.
Then INSTEAD of just pressure equalizing the battery pod and
allowing the pod to extend that equalization to the motor via
the flexible conduit going to the motor
steering shaft, I would seperately pressure equalize the motor and
battery pod. Here is exactly what I mean.
First install the tube onto the scuba
regulator that will replace the mouthpiece. Then attach a "T" fitting to
that tube unless I can find a "T" fitting that will attach directly to
the regulator and in that case omit the tube and just install the "T"
fitting directly to the scuba
regulator. Then from both ends of that "T"
fitting attach air lines. One of which will go to the battery pod and
the other that will go to the motor's hollow steering shaft. Then by
sealing with bondo, silicone, or epoxy both ends of the conduit
that carries the wires from the battery pod to the motor, I can isolate both systems, which will prevent any
however slightly remote possibility of hydrogen from ingressing into the
motor housing. But there is one more thing I would have to do as well to
make SURE the conduit would not transmit hydrogen from the battery pod to the motor. Since air or
hydrogen can actually seep thru the open ends of the insulation of the
wires and between the strands of insulated wires themselves, I would
have to do more than just seal both ends of the wire
conduit.
That would not be enough because the air/hydrogen could just seep thru the
wire's open ends and then thru the insulation even though the ends of
the wire conduit would be sealed. So to insure total air tight integrity
I will have to epoxy the wire ends themselves so that where the strands
of wire in the battery pod exit the insulation, the epoxy covers and seals the strands and insulation leaving
only the round connectors not epoxied at the ends of the wires.
That way the conduit between battery pod and motor is now sealed at both
ends with epoxy and the ends of each wire are also sealed against any air/hydrogen seeping thru the wires
themselves.
Although it might not be necessary to do
all this with the hydrolators and hydrocaps taking care of the hydrogen,
it still seems a good idea and potentially safer way to go since with
this method it insures (no matter how small the possibility)
that hydrogen could not enter the motor and and possibly ignite due to motor sparks.
Both the battery pod and the motor will
still be pressure compensated against the outside water pressure by the
use of just one scuba regulator. Just with seperate air hoses.
I am going to constuct a tray that will
hold my 4 batteries in the pod. This tray will slide out as a unit and
allow access to the batteries by unscrewing my pvc pod endcap when
needed to check the hydrocaps and hydrolators and also to check the acid
and water level
within the batteries..
But to avoid disturbing the large O ring
seal on the endcap every time I recharge, I will install a forced air
system in the pod that wil allow me to vent hydrogen out of the pod when
charging the batteries. I will only have to install one fitting because
the other end of
this forced air system will be the open end
of another tube that will contain the wires to go to the charger that I
describe immediately below.
Also I will install a short pvc tube into
the battery pod that will have a screw on waterproof cap with an O ring
seal. This tube will contain the wire ends that I will attach my charger
to so I will not have to remove the batteries every time to recharge
them.
In addition to all this I will have
absorbant diapers in the bottom of the battery pod just as a
precaution to help soak up any small amounts of water in the bottom of
the pod that may accumulate from the hydrolators dripping any water into
the bottom of the pod.
And the final component will be a leak
detector installed about one third of the way up the side of
one of the batteries so it will not give me a false reading that it
might if I installed in on the bottom where it might contact any wetness
on the absorbant diapers
that might be caused by small amounts of
water dripping from the action of the hydrolators.
After much research, personal thought and
taking into account other helpful member's advice from both this forum
and many other sites and forums, I believe this will be a safe and
efficient system for a battery pod and air pressure equalization
system.
Does anyone have any
comments?.
Kindest Regards,
Bill Akins.