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Old 26-01-2016, 11:48   #1
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No Negative Battery Switch or Battery Selector

Would like you get advice on my current battery configuration. On my 2006 Dufour 34, there are two positive (red) master battery switches - one for the two house batteries and one for engine battery. There is not a negative (black) master battery switch. There is also no battery selector switch (1,All, 2 Off).

Is there a concern with not having a negative master battery switch?

With two master battery switches, is there a purpose served by adding a battery selector switch, or is that redundant?
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Old 26-01-2016, 11:57   #2
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Re: No Negative Battery Switch or Battery Selector

I can't think of anything you could do with one master that you couldn't do with two.
Just have to have a little more smarts to operate two.
I've never seen the neg switched, I do not think it a good idea.
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Old 26-01-2016, 11:57   #3
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Re: No Negative Battery Switch or Battery Selector

Quote:
Originally Posted by B-to View Post
Would like you get advice on my current battery configuration. On my 2006 Dufour 34, there are two positive (red) master battery switches - one for the two house batteries and one for engine battery. There is not a negative (black) master battery switch. There is also no battery selector switch (1,All, 2 Off).

Is there a concern with not having a negative master battery switch?

With two master battery switches, is there a purpose served by adding a battery selector switch, or is that redundant?
Can't say, in my year of research into rewiring my batteries, I ran across a concern about a negative switch.

As for the positive switches, I doubt you need to add a selector switch to what you have. Maine Sail and Stu Jackson have written extensively on how the house and starter banks should be wired. See link below. If your bank is wired like one of the options or can be rewired to match, you are good to go.

Basic Battery Wiring Diagrams
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Old 26-01-2016, 12:02   #4
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Re: No Negative Battery Switch or Battery Selector

Well generally most systems do not have a negative off switch, it is considered good enough just to disconnect the positive.

Marine wiring can be very complex area and there are multiple threads here on it.

I would recommend to get you started: Basic Battery Wiring Diagrams
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Old 26-01-2016, 16:21   #5
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Re: No Negative Battery Switch or Battery Selector

Thank you for the replies, it was appreciated.
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Old 26-01-2016, 18:03   #6
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Re: No Negative Battery Switch or Battery Selector

A single battery selector switch (1-2-both-off) is a convenience, nothing more or less. I believe Beneteau used the separate switches on some models as well, and the point can be made that they are cheaper and simpler.


I've heard of battery negative switches being installed, to ensure the battery is cut off from any possible grounding/galvanic issues, but at least on US market boats, it is virtually unheard of. If your grounding and bonding are done properly, there should be no need or advantage to it, just "more stuff to fail". Although if you bury it well enough, you could justify it as a "secret switch" for security, making the boat harder to steal.
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Old 26-01-2016, 18:47   #7
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Re: No Negative Battery Switch or Battery Selector

I've run across a number of negative battery switches on European-made boats. As hellosailer said, they're non-existent on U.S.-produced boats, and I can see no good reason to have them.

I like the separate switches much better than the ubiquitous 1-2-Both-Off switches, because with this system you are less likely to make a mistake.

One ON-OFF switch connects the start battery to the engine solenoid/starter.

A second ON-OFF switch connects the house batteries to the house loads.

I like to install a third ON-OFF switch to be used as an emergency combiner switch, so that either battery bank (house or start) can be used to power the boat.
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Old 26-01-2016, 20:05   #8
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Re: No Negative Battery Switch or Battery Selector

It is common to have a negative switch between the batteries and the engine block on metal boats (to reduce hull electrolysis). House negative will typically not be switched as the house consumers can easily be 100% isolated from the hull.

Steve

Note: I still need to break out the label maker like btrayfors did above.
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Old 27-01-2016, 09:22   #9
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Re: No Negative Battery Switch or Battery Selector

Hi:

I have one specific instance of the use ( and need) of a negative disconnect. I have installed a solenoid on the negative to my windlass. I was able to avoid using the zinc of my chain as a galvanic sacrificial. My chain, specifically the 1st 5 ft in the water, lasted longer in the tropic. The negative to the diesel engine creates a loop through the prop shaft and/or the heat exchangers. The zinc in that circuit of diesel motor/anchor windlass is your chain galvanizing.

It is simple to energize the solenoid to engage only when the breaker to the windlass is switched on.

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Old 27-01-2016, 09:26   #10
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Re: No Negative Battery Switch or Battery Selector

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Old 27-01-2016, 10:47   #11
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Re: No Negative Battery Switch or Battery Selector

Quote:
Originally Posted by btrayfors View Post
...

I like to install a third ON-OFF switch to be used as an emergency combiner switch, so that either battery bank (house or start) can be used to power the boat.
Attachment 117721

Bill
Bill-We have accomplished the same thing with a momentary push button switch on the instrument panel that activates a solenoid that links the house batteries and start battery to allow one to use the house batteries to start the engine if necessary.

In re: the OP's question, I can see no benefit to a Negative switch in addition to switches on the positive side of a circuit.
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Old 27-01-2016, 10:58   #12
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Re: No Negative Battery Switch or Battery Selector

Blue Sea makes a single rotating switch that does everything you will need on a small boat: Top position is all OFF. 90 degrees clockwise is ON for both HOUSE and START but the two are isolated from each other. 180 degrees clockwise is ON for both HOUSE and START but they are ganged together for emergency starts. I know, I know, what happen if it fails? Well if you don't have the proper tools and spare parts (extra cable & clamps) onboard and the knowledge and skill to use them perhaps you shouldn't go to sea
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Old 27-01-2016, 12:07   #13
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Re: No Negative Battery Switch or Battery Selector

If you interrupt the neg. side from the battery about every neg. lead on your boat become a pos. through your equipment if the pos. hasn't been. Someone else may comment on the possible effects of your electronic not having a path to ground?
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Old 27-01-2016, 12:29   #14
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Re: No Negative Battery Switch or Battery Selector

Quote:
Originally Posted by Panope View Post
It is common to have a negative switch between the batteries and the engine block on metal boats (to reduce hull electrolysis). House negative will typically not be switched as the house consumers can easily be 100% isolated from the hull.

Steve

Note: I still need to break out the label maker like btrayfors did above.

Trying to follow your layout and would love to see what is doing what. Please post once you get it labeled


edit: looks like the left switch is for start bank, center is to combine, right is house bank, and the bottom switch is for neg off. Do you have the neg floating? If so, does it connect to both banks before the switch?

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Old 27-01-2016, 12:34   #15
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Re: No Negative Battery Switch or Battery Selector

Simply, there is nothing wrong to implement negative switch.
Could be even reason behind, for example in case the house & start.
batteries are weak. ...switch them both in serial combination
to star the engine. On the other hand in your house wiring to disconnect
anything else than active is illegal .
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