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Old 10-10-2010, 10:21   #1
MPB
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Any Ideas About Using an AC/DC Converter for Dockside ?

After leaving the boat at the dock, turning on the shore power and the battery charger, we turn everything off (except for the bilge pumps of course). But the one thing I would like to keep running is the 12vDC refrigeration unit.

Due to its ongoing consumption, the battery charge will obviously have to cycle more often, which has a negative impact on the batteries, I believe.

In essence at dock I want to power the refrigeration directly from the AC/DC converter (no battery usage at all). At sea, I would switch back to the normal 12v system.

So if I wire-up a converter (for example a Tripp Lite 20amp) through the AC panel, and subsequently through a Double throw switch ( to switch from dock side usage to the standard 12vDC panel), would I solve my dilemma ?


Looking forward to being enlightened !
Thanks
Miguel
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Old 10-10-2010, 10:29   #2
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Yes.
The Refer' + supply in would be connected to "Common"
The Battery + would be connected to "A"
The Converter + out would be connected to "B".
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Old 10-10-2010, 10:35   #3
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Gord,
Thanks for the wiring diagram.
Re the "makes sense" part of my question, can I assume you agree ?
Miguel
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Old 10-10-2010, 12:13   #4
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... Re the "makes sense" part of my question, can I assume you agree ?
Miguel
Yes, you may.
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Old 10-10-2010, 12:26   #5
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A couple of notes of caution. Any 12v supply needs to be very well regulated to supply a constant 12v particularly to a fridge with sometimes very high current start up demands. A battery filters out the spikes.
The second problem is how you will isolate the negative if this is connected to earth you can get some bad corrosion problems in a marina.
I think unless you know what you are doing you would be better to keep the batteries in the circuit. The batteries may well even benefit if the charger is a good one.
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Old 10-10-2010, 12:28   #6
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MPB, When I leave my boat I turn off everything but the bilge pumps and the refrig. My refrig draws about 5 amps when it's running. I have never found my charger putting out anything but the float voltage in this mode. Essentially the charger is providing the 5 amps it takes to run the refrig. The battery is not doing any significant cycling. Also when you're away from the boat and not opening the refrig it runs a lot less than when you're there. Our house batteries are almost 9 years old and still going, though I do note their capacity is down a bit (2x 215amp lifeline AGMs). Our charger is a Xantrax 40 amp. I don't think your plan will cause any problems, I just don't know if it's worth the trouble.
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Old 10-10-2010, 13:38   #7
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I agree with Captain Bill. Your best plan is to continue to run the fridge off the house batteries and allow the charger to do it's thing in float mode. Running the fridge while float charging the batteries will not decrease your battery life even slightly, IMHO. Simpler, better, cheaper.
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Old 10-10-2010, 13:48   #8
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When dockside I've always just had the charger plugged in. I've no 120VAC stuff other than the charger. Leave the pumps and fridge on. The batteries like it. It's a good 10A charger, that's all.
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Old 10-10-2010, 13:50   #9
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My fridge came with a 120ac - 12dc adapter I mounted it but never used it 12v-dc all the time No issues
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Old 10-10-2010, 14:01   #10
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Ok Everyone !!

Thanks so much for the very valuable input, which I will follow.
Now that I don't have that project to worry about, I guess I'll go sailing, instead.

Thanks again!!
Miguel
P.S. I will think of something soon however, to challenge you all again
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Old 10-10-2010, 14:04   #11
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Sounds like a solar pannel could be an option
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Old 11-10-2010, 01:25   #12
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If you really want to do this, then I'd get another small battery and make your AC/DC converter simply run off of this supplemental assembly -- i.e., you would make a Battery Bank #3.

As for the electrolysis issues, I too would concerned with what you might be doing to others and what your little converter might be doing to your boat. If you do it, at least add a relatively large zinc to your protection system on the boat (a Grouper sized one :^) )
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Old 11-10-2010, 18:22   #13
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Quote:
Originally Posted by MPB View Post
After leaving the boat at the dock, turning on the shore power and the battery charger, we turn everything off (except for the bilge pumps of course). But the one thing I would like to keep running is the 12vDC refrigeration unit.

Due to its ongoing consumption, the battery charge will obviously have to cycle more often, which has a negative impact on the batteries, I believe.

In essence at dock I want to power the refrigeration directly from the AC/DC converter (no battery usage at all). At sea, I would switch back to the normal 12v system.

So if I wire-up a converter (for example a Tripp Lite 20amp) through the AC panel, and subsequently through a Double throw switch ( to switch from dock side usage to the standard 12vDC panel), would I solve my dilemma ?


Looking forward to being enlightened !
Thanks
Miguel
Miguel, with respect you are seeking an unnecessary solution with its attendant complications.

If you have a smart switch mode battery charger there is no need to disconnect the batteries whilst on shore power. It will float the batteries & cover any necessary current drain up to its full capacity. The only issue would be in ensuring wet cell battery electrolyte continued to cover the plates.

In fact leaving a smart charger running particularly one with an auto de-sulphation cycle can only have a positive effect on battery life.
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