Early winter project report

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Early winter project report

Postby Breakin Wind » Sat Dec 08, 2012 1:30 am

Greetings all,

Because of the unseasonably warm November this year in Minnesota, I've gotten a good head start on my winter projects already.
I think there was a recent re-discussion about batteries, cables and volt/current meters (maybe that was last year), but I found a really great deal on e-bay for a dual display Voltage/Current/Power digital meter. $25.00 shipping included. (8-40vdc - 50A). The advertisement claims it can also display power, capacity and time but I've not figured out how to read/interpret those displays yet.
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Each display is completely switchable and could be configured to measure voltage on two batteries if you're setup for that rather than voltage and current on one. I will use it next summer for both monitoring voltage/current consumption and also Volts/Amps during charging.

I mounted it in a small cabinet I built just inside the cuddy along with a fused switching panel for bilge pump, AC inverter (therefore the outlet) and lighing. (I need to re-label the switches when it gets warm again).
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To the left of the panel is a space for my dock bumpers and to the right, you can just see the back of a pass-through for 15 ft. of cable to plug into my 12volt dock charging system.
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Forward of the cabinet on the port side, you can see a storage area I built in for my rudder when docked, and my boom/mast crutch while sailing. There is a netting cover to keep things from bouncing out under rough conditions. The cuddy sole is covered with a 3/4" thick plastic tile with drains. Very comfortable to kneel or sit on, lightweight and with anything short of a capsize, will keep all my storage away from any water that intrudes into the cuddy.
In the lower front center you can see the step/seat that covers the two battery boxes, battery switch and my converted centerboard uphaul mechanism. As mentioned, I have the bilge pump switch on the power panel for manual pumping and a high mounted float switch under the sole that kicks in if the water gets too deep in the bilge when the boat is unattended.
I'll have to disassemble everything this spring to finish & waterproof the wood pieces, but it's moving along nicely so far.

Thanks - Scott
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Caution

Postby GreenLake » Sat Dec 08, 2012 6:06 am

Scott,

I'm not sure I'd ever recommend using an AC converter on a small boat like this; especially not one that isn't very obviously equipped with ground fault interrupt protection...
~ green ~ lake ~ ~
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Re: Early winter project report

Postby GreenLake » Sat Dec 08, 2012 6:14 am

Other than the perhaps not so safe addition of the AC converter, I get the impression that you are coming along nicely in converting your boat for cruising on a more ambitious scale than your local lake will support. Your panel housing, storage shelf and bench give a nice and solid impression. Before you finalize your design by sealing the wood, take measure of how much weight you are adding. The DS is not really overpowered as it is, and any weight you add will be painfully felt on all the days where you have the merest breath to work your boat with.

Once it's done, where will you go to get the best benefit of such a nicely fitted out boat?
~ green ~ lake ~ ~
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Re: Caution

Postby Breakin Wind » Sun Dec 09, 2012 1:25 am

GreenLake wrote:Scott,

I'm not sure I'd ever recommend using an AC converter on a small boat like this; especially not one that isn't very obviously equipped with ground fault interrupt protection...


Thanks GL,

Not so sure what the concern would be about 110VAC on a boat. I've used a small generator for years on our pontoon during our annual 4th of July night boat parade and although I've not really researched it, from what I know and can extrapolate, I can't think of why it would be a problem.

As far as a ground fault goes, again not having really researched it specifically, I should think an "ungrounded" system is probably somewhat safer. In a grounded service (as in your home), the neutral side of the outlet (large hole on the outlet or white wire) is actually connected to physical ground (earth) at a number of places. So if I am standing barefoot on damp dirt, and touch the hot side of the outlet (the small pin or colored wire) with my finger, some amount of current will flow through my body into the ground. 110VAC likely won't kill me even in that case, but it'll make me think twice about doing that particular thing again.

In my inverter case, The AC circuit path is a closed loop where the neutral side is not connected in any way to the boat or anywhere other than the plug for that matter, and therefore other than the return wire going back to the inverter there is no other possible return path with which to get a shock. I could be standing in a puddle of water in my DaySailer cockpit (or floating in the lake) and put my finger on the hot side of the AC power and get nothing from it at all. There is no return path for the electricity to flow through my body back to the return side of the AC circuit.

I guess I can't say I know that is a scientific fact, but it should be very easy for me to test my thinking (which I will do next time I'm at my boat) but I can't imagine how else it could work. I'll assert that if I place one lead from my AC Voltmeter on the hot side of the inverter, there is no-where I can touch the other lead to register a voltage other than the return side of the plug.

If I were to bridge both terminals with a couple fingers or one in each hand, then I'm going to get a shock, but that is something one isn't supposed to do in any case, and that would happen regardless of a whether a system is grounded or not.

At least that's my thinking - Thanks - Scott
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Re: Caution

Postby GreenLake » Sun Dec 09, 2012 6:58 am

Breakin Wind wrote:I guess I can't say I know that is a scientific fact, but it should be very easy for me to test my thinking (which I will do next time I'm at my boat) but I can't imagine how else it could work. I'll assert that if I place one lead from my AC Voltmeter on the hot side of the inverter, there is no-where I can touch the other lead to register a voltage other than the return side of the plug.


I think this might work, but only as long as you don't have any stray connections, by whatever means, e.g. moisture. Please don't try this out, but I was thinking also of extreme situations, like you are running the inverter when the boat capsizes.

You're right that if both poles float, then there isn't even a way to detect current loops being closed through your body. Anyway, whether the theory works or not, I'd personally feel uncomfortable with such a setup on a dinghy.
~ green ~ lake ~ ~
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Re: Early winter project report

Postby jdoorly » Mon Dec 10, 2012 2:36 am

This link covers inverter safety:

http://www.tekrispower.com/pdfs/xantrex/Grounding%20Inverter-Chargers%20on%20Boats.pdf

Without a propeller shaft, etc, there isn't much to worry about, although I would be careful to fuse any extension cords out to a floating boat.
DS2 #6408 "Desperado"
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Re: Early winter project report

Postby Breakin Wind » Mon Dec 10, 2012 9:46 am

Thanks again guys, greatly appreciate the inputs. I don't anticipate using the inverter often, but similarly, I've always got one stuffed under the seat of both cars "just in case". I've pulled them out before to charge a laptop, to power a small clip on fan and those kinds of things.

As seems nearly always the case, an answer from one discussion spawns a question from another direction. I could make this a long story, but it still wouldn't change the base question so I'll spare you an hour of reading. I purchased a large wheeled charger last year at a flea market (2A/20A/200A) and discovered through some random activities that the metal case of the charger seems to be common with the Plus side of the 12vdc output. I've looked inside and can't find anything that looks like it's not where it belongs but I guess I would have expected either the case to be isolated from the DC side, or if grounded to the secondary, for it to be on the negative side.

Does anyone have a thought or practical experience why this would be set up that way on purpose? As with my inverter argument, the DC side of the charger doesn't really interact with the outside world as it's either clipped to a battery for charging or not, but it just seems wrong to me. If I can't find anyone (here or in other circles) to give me a good reason for it, I'll probably pop the case open this winter and look again for fault or error that's causing it, and maybe lift the connection and move it to the negatve side (or float it). I'd expect the case to be grounded to the outlet ground, just can't think of why it would also be grounded to the +12vdc side.

Other than the potential use of batteries on boats etc., I realize this question has little to do with sailing, but there are some very smart and extremely experienced (both in sailing and life) people here so I'll ask anyway.

Any thoughts or guesses?
Thanks - Scott
Breakin Wind
 
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Re: Early winter project report

Postby GreenLake » Mon Dec 10, 2012 1:45 pm

Scott,

by tying one of the DC outputs to ground, you get the effect that any stray connection of "hot" AC to any part of the DC circuit will blow some fuse somewhere. If that ground connection is missing, the entire DC circuit could be AC "hot" and you could touch it, think it's safe, but complete the AC circuit to ground. That's the only chain of reasoning that I can come up with on the spot.

For boats, the ABYC has created some specifications that you could read, but, as they are intended for builders, they are not available for free. I think there's somebody who wrote a decent book about boat electrics. As I never planned on any permanent installation, I haven't read extensively in that direction. Here's something I found that might help: http://www.cruisersforum.com/forums/f127/best-boat-electrical-books-39313.html
~ green ~ lake ~ ~
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