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Battery Switch wiring OFF / 1 / 2 / 1+2


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So i have an issue with a boat we dont use much (trying to sell) which has a bilge pump that runs every few minute to check for flow (instead of a float switch). 

When i leave the boat without starting it for a month, it seems to drain the batteries. 

If i install a OFF / 1 / 2 / 1+2 switch, which has the 3 terminals on the back, do i wire all the accessories to the switch also? or do i leave them on the battery. It seems like the switch just directs the charge current and starting power btween the batteries.... but the accessories can still run even if the boat is off?

Right now it have it set like this:

COM Terminal: Starter

T1: Battery 1 

T2: Battery 2


Or should i jsut disconnect the batteries when leaving it for extented period of time? 


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32 minutes ago, agarabaghi said:

it seems to drain the batteries. 

If i install a OFF / 1 / 2 / 1+2 switch

So your boat has more than one battery and the switch is NOT a 1/2/1+2/OFF switch or no switch are all? 

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it has a digital battery isolator for charging, basically it would sense voltage and automatically decide which battery would get charge. 

We were rewiring the setup and go rid of the digital isolator because it was all corroded. 

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Ok, but that would be specific to the distribution of the alternator charger, no other loads. A charge control can also, and is typically use, in conjunction with a main manual switch. Sounds like Malibu did not use the switch, just the charge device? 

In short, all loads would wire to the COM terminal, except the auto bilge. However, that still leaves you pretty much where you are with that type of water sensing bilge. Its still going to cycle and in reality, its still a safe idea to have it wired battery direct. So, your choice to wire it to the boat side of the switch or leave it. Or as minmarker suggested, swap it for a traditional 3-wire bilge with internal float or water level sensor. 

With no switch and all loads wired battery direct, the bilge may not be the reason both batteries are dead. Without a schematic, I dont see how a bilge bump cycling is drawing down two batteries. 

Forgot to ask, was is a promariner charge control? 

Edited by MLA
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its not a malibu and it was all installed by me. 


Its an older 2006 x1, and we added a 2nd battery to help with the stereo draw. Now ive removed most of the stereo but wanted to leave the dual battery setup. Yea im not sure the bilge is causing the drain but its the only thing i could think of that would still be drawing some current 

Unless the batteries are bad/

Edited by agarabaghi
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so i should wire all loads to the com terminal on the switch, and if the boat is in the water i could leave it on #2 to let the bilge get power, but if its on trailer i could flip everything to off and it should help keep the batteries from draining?

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Never heard of a bilge pump that worked like that but you may have helped me solve why my jet ski battery died. 

Yeah just wire it like that or you can use a simple on/off switch to isolate one of the two batteries. Make sure the pump isn't wired straight to the battery. 


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the pump is wired to the dash switch etc... 

i will try wiring all the accessories to the com terminal. I will probably have to wire everything to a distro block then from there to the com to limit he numebr of wires are switch


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I think you got a good answer there.  

To add perspective..Nautique uses the Stooopid load sensing bilge pumps that draw a load on the battery every minute or two as well.   It is a tiny load they draw, and a healthy battery should last weeks that way.  They wired it to the switch, so when you turn the switch off, you also turn off the boat's life vest.  There are folks who have left their boat in the water, turned off the switch, and found it full of water the next morning, due to what should have been a relatively minor leak.  Other folks find themselves with a dead battery after an extended period of time.  

I know float style bilge pumps can get full of debris and get stuck, but I think they are better, IMHO.  It is just a matter of picking your poison.  

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true since re wiring this boat wont cost me anything im gonna try that first. I might also start disconnecting the battery terminals until we put it in the water to show it for sale.

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