From: lil_brother_llc@bellsouth.net
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 -----
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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