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Old 23-11-2020, 19:16   #1
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What might it be?

Digging through the maze of wiring on our new to us boat, I ran across the device in the picture. There are some faint markings, the two outside terminals are marked 1 and 2, the center one is A. The terminal with the wire on it went to +12VDC. There is a wire hanging close to the other outside terminal, no lug, but it goes to DC ground.
I think there is more wiring on this damn boat than there is in our house.


Any thoughts on what that might be?


Thanks,


Bob
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Old 23-11-2020, 19:46   #2
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Re: What might it be?

Galvanic isolator?
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Old 23-11-2020, 19:47   #3
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Re: What might it be?

My GUESS is it is a diverter, probably for a wind generator. When the voltage gets too high then the load is shunted to some resistors.
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Old 23-11-2020, 19:50   #4
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Re: What might it be?

Schottky Diode Battery Isolator...?


http://www.ase-supply.com/Sure_Power..._p/sp-702p.htm
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Old 23-11-2020, 19:51   #5
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Re: What might it be?

Looks like a two-battery diode isolator. Alternator output goes to A, start battery positive to 1, house battery positive to 2.

Old tech, inefficient, replace with ACR or FET-based separator.

https://www.dbelectrical.com/product...ne-rv-ems.html
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Old 23-11-2020, 19:53   #6
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Re: What might it be?

My first though was a dumpl load for a wind generator, but then I thought: Galvanic Isolator? Similar to this Sterling one:




But then again, it could be a batter isolator

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Old 23-11-2020, 19:59   #7
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Re: What might it be?

#4 & #5
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Old 24-11-2020, 08:24   #8
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Re: What might it be?

Battery isolator sounds reasonable although the wiring makes no sense. Only one terminal connected to a very small gage wire to +12VDC. Only other wire in the neighborhood went to DC ground but was not connected to the unit. Only one of many strange electrical things on this boat.
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Old 24-11-2020, 08:53   #9
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Re: What might it be?

Indeed, it's a diode based isolator.
I cannot explain the improper wire size & connections you describe.
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Old 24-11-2020, 09:17   #10
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Re: What might it be?

Here's a couple of photos of a Guest 2401 Battery Isolator in black. Looks pretty similar except color.



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Old 24-11-2020, 09:29   #11
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Re: What might it be?

Why wonder, do you want to connect it to something?. Isolating diode is the easy way to charge 2 batteries. If the diode can handle the amps from the alternator output , you could connect it to your two batteries and your alternator. That way the current flows to the point of least resistance, the flatter battery and charges that one. Middle terminal is wire from alternator, others are to each battery. Other advantage is the the current only flows one way, from alt to batteries and not back to alt...this is a good feature as adds some safety that the alt when stopped sees no power from the big red wire. If only one battery, then connect both outputs to the same battery and spread the load between the two diodes. Read up about isolating diodes and also the voltage drop.
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Old 24-11-2020, 11:01   #12
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Re: What might it be?

Was this unit connected when you found it? If others are correct in saying it is a diode based battery isolator, then I would agree it would be better replaced with an ACR (automatic charge relay) as in https://www.bluesea.com/support/arti...R%5D_Explained
I understand (vaguely) that the problem with diodes is you get voltage drop which you dont get with an ACR. I have had an ACR on my boat for many years with no problems.
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Old 24-11-2020, 11:04   #13
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Re: What might it be?

If it was disconnected , maybe it has already been replaced but just left on board ???

New (to you) boats are a bit like a jigsaw puzzle - my wife loves them but mine are more of a practical nature. Am struggling right now with a swimming pool boiler...
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Old 24-11-2020, 11:18   #14
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Re: What might it be?

I'd guess a diode isolator. It carries some current thus the cooling fins.
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Old 24-11-2020, 11:37   #15
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Re: What might it be?

It only had the one wire connected. It wasn't anywhere close to the battery cabling which is under the floor in a different cabinet. I cleaned all that up before we brought the boat home. Currently there is a 1,2,both,off switch which will be replaced with a ACR in the future.
Thanks for all the responses, diode isolator it is. Another item to donate to the dumpster.
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