Two Batteries and a Bilge Blower

[triman]

Conventional wisdom is that if you have 2 or more batteries, one should be dedicated purely to the engine and the other for all other electrical loads.

Now, here's the question.

I'm working now on the maintenance plan for next year. The engine will be removed and rebuilt, the leg overhauled, the hull gone over in entirety and I try to source a chunk of teak to make a new dashboard and 1 sub-board.

With the boat partially gutted I want to sort out a minor glitch or two I have in the wiring and I also need to decide where 2 very important engine-related items are wired.

I'm going to build a bilge sniffer and I have a bilge blower. As well, there will be 2 bilge pumps.

And what of the engine gauges?

So, are these basic, but essential items wired to the engine battery or the house battery?

Your advice will be appreciated.

 

[Silvertip]

Re: Two Batteries and a Bilge Blower

Your conventional wizdom is flawed -- but just a bit. Just because you "desire" a dual battery system, does not automatically imply that all loads need to be on the house battery and the starting battery used just to start the engine. Lets start with the gauges. Gauges are powered from the engine wiring harness, not the boat harness. Therefore, when you turn the key on the gauges get power. That would not be the case if they were powered from the house battery and besides, you would then need to add a separate switch to turn them on and off. Does the term "forgetful" come to mind with this system. Next, unless you add a dual battery switch, isolator, or combiner, the house battery does not get charged from the engine alternator. So what you really need is to install a dual battery switch (provides the most flexibility at minimum cost) and wire everything, including the engine to the COM terminal on the switch. Everything that is except for an automatic bilge pump which should be wired directly to the house battery. You now have the option to kill all electrics (switch OFF), start the engine on either or both batteries, charge either or both batteries, and power everything from either or both batteries by simply setting the switch to BAT 1, BOTH or BAT 2. Adding dual batteries is not done just to "split the load". It is done for electrical system redundancy. It doesn't make sense to have two completely separate electrical systems and not be able to fully utilize both of them - especially in an emergency.

 

[triman]

Re: Two Batteries and a Bilge Blower

My apologies. I have all that. Just wondering whether the bilge blower and bilge sniffer should run off the house or engine battery

 

[Silvertip]

Re: Two Batteries and a Bilge Blower

Doesn't matter. It all depends on how you run the switch when under way.

For others reading this thread, see how just a little bit of detail could have saved me (or someone else) a great deal of time? Details, Details, Details. Always provide details as we cannot see your boat! Details eliminate a lot of the back and forth questioning that often results when we need to drag information from posters.