James,
I will be looking at this very closely, thank you for the comments.
I am likely to make those two pods AC and, keep things well managed, the thrusters however, I think most probably DC. It would be too much to worry about stray currents in proximity to divers so, managing two is easier. Besides, these are likely to be modified Minn-Kotas anyway.
In looking at this casually at this point, it seems to me that denying the inverter power absolutely at will and or automatically in a pinch, ......is a key issue.
Joe
From: "Lil Brother LLC" <lil_brother_llc@bellsouth.net>
Reply-To: personal_submersibles@psubs.org
To: <personal_submersibles@psubs.org>
Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
Date: Tue, 7 Aug 2007 21:50:34 -0500
>Joe,
>
>There would be a breaker connected in the system like a GFI plug that goes
>in a bathroom or in the kitchen of your home.
>
>The system would kill the power (preferably close to the battery (s)) and
>prevent the crew compartment from receiving power in the flooding stage. You
>could also do this manually.....but there could be problems with this
>method. There is not a good solution to the problem. With a GFI circuit
>.....you could lose power when you actually needed it. With the manual
>method....you could still have power when you don't want it.
>
>You could also just put in a GFI for just the inverter system.....but you
>would still be left with DC in the water....which could be uncomfortable
>depending on the dispersal of the power(in the water).
>
>All of the power distribution boxes could probably be made water tight. The
>only element I know of that would be difficult is the inverter itself. Most
>inverters are built with some type of air circulation for cooling. If you
>are having a custom inverter made.....it could be built water tight and use
>the hull as cooling (this can be done....although it would require some
>careful planning).
>
>All of this is very subject to useful service life as well. If you do plan a
>total water tight power distribution, it should be checked a couple times a
>year.
>
>There are many ways to make the situation safer (or better) you just have to
>decide how far you want to take it.
>
>James Long
>Owner/Designer
>Lil Brother LLC (Instrument Division)
>----- Original Message -----
>From: "Joseph Perkel" <joeperkel@hotmail.com>
>To: <personal_submersibles@psubs.org>
>Sent: Tuesday, August 07, 2007 4:53 PM
>Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
>
>
>James,
>
>....Interesting comments, thanks.
>
>Say for example, I was to invert 48V to 230V AC in order to run a couple of
>AC induction motors in pods. Why,..one moving part for one thing, 90
>percentile efficiency at full rpms, continuous duty rating and, a two to one
>price advantage over DC in the 5-10 hp range, ....this is several $K,
>perhaps as much as 6K for two.
>
>So, as I understand it, I energize this inverter via a DC distribution
>box,...correct?, so then in case of flooding, who denies this inverter
>power??, the crew with a throw switch, or some type of breaker?
>
>Joe
>
> >From: "Lil Brother LLC" <lil_brother_llc@bellsouth.net>
> >Reply-To: personal_submersibles@psubs.org
> >To: <personal_submersibles@psubs.org>
> >Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
> >Date: Mon, 6 Aug 2007 22:31:09 -0500
> >
> >Brent,
> >
> >The problem with an A/C system in a sub is actually two fold. Let me
> >explain:
> >
> >A/C is used for electrical lines because of the use of ground (earth). Most
> >A/C components have an external grounding point incase something goes wrong
> >inside and causes the whole component to become "live". With a system in a
> >submersible.....you would not only have to provide the two wires to run the
> >equipment, you would also have to provide the extra ground fault system to
> >ensure no power is being leaked into the water or the hull. The electrical
> >design could get pretty complex.
> >
> >This is not the same as driving a three phased brushless DC motor....this
> >is much more complex.
> >
> >Also you have to consider the ramifications to the marine life if something
> >does go wrong.....you could kill quite a few fish/animals if your power
> >were to get into the water.
> >
> >I don't think you could ever totally isolate the interior (from electrical
> >inclusion from flooding) to prevent power absorption, it would be nearly
> >impossible. It would be much easier to place a ground fault system in place
> >to kill the power if it detected the situation.
> >
> >The problem with A/C....you don't know which way the current will go. It
> >will take the path of least resistance.....which may not be the direction
> >you plan for it to go. An A/C power system requires very careful
> >planning......if you want to use it in a psub.
> >
> >Also.....as in a previous message....you do not want your hull to have any
> >electrical potential for it causes electrolytic problems.
> >
> >James Long
> >Owner/Designer
> >Lil Brother LLC (Instrument Division)
> > ----- Original Message -----
> > From: Brent Hartwig
> > To: personal_submersibles@psubs.org
> > Sent: Monday, August 06, 2007 8:02 PM
> > Subject: RE: [PSUBS-MAILIST] Battery Safety Issues
> >
> >
> > James,
> >
> > You bring up a point I was thinking about with regards to grounding the
> >batteries to the sub. Most paints don't have much if any electrical
> >insulating properties, so the electrical charge, if it's AC power, would
> >just migrate through the hull and then out to the surrounding water, and
> >then into the ground, right? If it's DC power then it's just going to keep
> >mostly to it's self between the negative and positive points or leads? So
> >what I'm getting at is that if a sub is built with syntactic foam and/or a
> >heavy coating of Rhino liner type coating, (of which one or both are likely
> >to be good electrical insulators) on the interior of the sub, wouldn't the
> >AC power then have a harder time getting out of the sub, unless the power
> >systems were grounded to the sub, so the power can get out easier? I was
> >just thinking that if the power has to leave through the area where the
> >leak is, and/or through the open hatch, or which your trying to leave
> >through, you would get a real nasty or deadly shock. Especially since allot
> >of leaks are jumped on by the operator(s) of the sub, to fix them.
> >
> >
> >
> > Regards,
> > Brent Hartwig
> >
> >
> >
> > > From: lil_brother_llc@bellsouth.net
> > > To: personal_submersibles@psubs.org
> > > Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
> > > Date: Mon, 6 Aug 2007 14:07:56 -0500
> > >
> > > Joe,
> > >
> > > I think that is a somewhat different type of issue. Remember that AC
> >doesn't
> > > require much to shock you. Just providing a path to ground (earth)
> >will get
> > > you shocked. On the other hand DC will only shock you when you provide
> >a
> > > path to it's opposing pole.
> > >
> > > I can see why you wouldn't want your shore power energized when
> >cleaning the
> > > bottom on your boat. A/C is sometimes "leaky"(motor cases, pump cases,
> >etc.)
> > > and the leak would be finding it's shortest path to ground(earth). If
> >you
> > > got it that path.......it would be a bad thing(depending on the
> >current
> > > present). I refrain from working with A/C as much as possible.....but
> >there
> > > are cases A/C is the best method.
> > >
> > > Being in a psub filled with water (with submerged batteries) wouldn't
> >be a
> > > joy ride, but I don't think it would be much more than a tingling
> >sensation.
> > > I don't think you would be worried much about the tingling sensation
> >anyway.
> > > You would have more important things on your mind. But I also would
> >try to
> > > have my power leads pretty close to each other.....not separated on
> >each
> > > side of the hull. But the design requirements for most electrical
> >systems
> > > will have the lead close anyway.......wouldn't be much use if they
> >were not
> > > connected to the same system. Also...I wouldn't connect my hull to the
> > > negative side (as most craft are...like cars).......could present a
> >problem.
> > >
> > >
> > > James Long
> > > Owner/Designer
> > > Lil Brother LLC (Instrument Division)
> > > ----- Original Message -----
> > > From: "Joseph Perkel" <joeperkel@hotmail.com>
> > > To: <personal_submersibles@psubs.org>
> > > Sent: Monday, August 06, 2007 1:36 PM
> > > Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
> > >
> > >
> > >
> > > James,
> > >
> > > Thank you for the info. I remember reading an article once with
> >respect to a
> > > "zone" while cleaning your boat bottom dockside. I cannot remember the
> > > details, or why it was an issue, something regarding stray shore power
> > > currents.
> > >
> > > In any case, I will look over the electrical details from a safety
> > > perspective in great detail.
> > >
> > > Joe
> > >
> > > >From: "Lil Brother LLC" <lil_brother_llc@bellsouth.net>
> > > >Reply-To: personal_submersibles@psubs.org
> > > >To: <personal_submersibles@psubs.org>
> > > >Subject: Re: [PSUBS-MAILIST] Battery Safety Issues
> > > >Date: Mon, 6 Aug 2007 12:27:37 -0500
> > > >
> > > >Joe/Brent,
> > > >
> > > >Yes...you will get some shocking effect, but it will not be severe.
> >The
> > > >kill
> > > >zone with the battery submerged (or breaker box) will be in-between
> >the
> > > >positive and negative poles of the battery/connection.
> > > >
> > > >Remember there are underwater welders that deal with this all the
> >time. It
> > > >is an uncomfortable thing to do....but is not life threatening, until
> >you
> > > >enter the kill zone.
> > > >
> > > >James Long
> > > >Owner/Designer
> > > >Lil Brother LLC (Instrument Division)
> > > >----- Original Message -----
> > > >From: "Joseph Perkel" <joeperkel@hotmail.com>
> > > >To: <personal_submersibles@psubs.org>
> > > >Sent: Monday, August 06, 2007 7:03 AM
> > > >Subject: RE: [PSUBS-MAILIST] Battery Safety Issues
> > > >
> > > >
> > > >Brent,
> > > >
> > > >This is one of those issues in the "back of my mind" as well. I
> >figured to
> > > >delve in further at the proper time but, perhaps someone can
> >elaborate.
> > > >
> > > >Joe
> > > >
> > > >
> > > > >From: Brent Hartwig <brenthartwig@hotmail.com>
> > > > >Reply-To: personal_submersibles@psubs.org
> > > > >To: PSUBSorg <personal_submersibles@psubs.org>
> > > > >Subject: [PSUBS-MAILIST] Battery Safety Issues
> > > > >Date: Sun, 5 Aug 2007 21:22:09 -0700
> > > > >
> > > > >
> > > > >
> > > > >If you have one or more batteries in the pressure hull with you,
> >and not
> > > >in
> > > > >a sealed off area, how do you keep from being electrocuted, if the
> >inner
> > > > >hull floods? Will not the batteries short out in fresh water, and
> >even
> > > >more
> > > > >so in saltwater? I would love to be enlightened. ; )' Perhaps
> >someone
> > > > >else wants and/or needs to know as well.
> > > > >
> > > > >Even if the batteries are in pods, or another hull section, will
> >not the
> > > > >breaker box cause and other wire cause your trouble?
> > > > >
> > > > >
> > > > >Regards,
> > > > >Brent Hartwig
> > > > >
> > > > > " I kind of like doing the impossible. "
> > > > >
> > > > > ~ Walt Disney
> > > >
> > > >
> > > >
> > > >
> > > >
> > >
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