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Changing the PO electrical setup (1 vs 2 house banks)

Hagar2sail

Member III
Blogs Author
So the previous owner of our new E35-3 did some rather interesting electrical work. Not interesting in quality, that seems pretty good. But interesting in choices. I have included a basic schematic of the electrical system as I understand it right now. As well as a few current pictures of locations of things.

In general I am trying to wrestle with the idea of if I want to continue using his method of two individual or isolatable house banks. From talking with him he always ran them in “both” so typically it acted as one big bank. However the choice of having two banks as currently installed has a lot of issues with charging unless your primary method is through shore power (which is how I believe he did it, I found a inverter-generator manual onboard and think the boat was at a marina in general).


As currently wired when the engine is running only the engine battery gets charged unless you turn on the “emergency bonding” switch. If your bank is way down on charge linking a mostly charged engine start battery seems like a bad idea.


Also, the engine battery is a flooded battery but the house batteries are AGM. The charger (which has three channels) is set to AGM. It is a Xantrex truecharge 40 but it can’t be set for different chemistries per channel. So I believe this chronically undercharges the flooded cell.


Finally my biggest concern is that this summer I want to add some solar to the boat since we will be keeping it on a mooring.


I think I have a few options to make this work.


1. I can put a battery combiner between the engine battery and bank #1 and another one between #1 and #2 (the banks are not physically separated). Then the engine and future solar charge the engine battery and house bank. No other wiring changes required.


2. Connect the future solar to the common on the 1-2-both switch and then never turn that switch off. If it did get bumped by accident then I think I might ruin a solar controller, so that in my mind is less than ideal. I haven’t seen any solar controllers that will charge two banks either. Or those are probably expensive. On this method the engine battery would need a charge combiner and the engine wouldn’t charge the house except if combined as stated above.


3. No longer use the 1-2-both switch. Change the house bank to one big bank. Then I can charge either the house or the engine with solar and link with a charge combiner.


Random musings....


The current Blue Sea Systems DC panel has a shunt on the negative but this is reading all batteries. Can I put a separate shunt for the house batteries in place to run a battery monitor off of? I don’t know if multiple shunts causes problems. I wouldn’t think so...


Is there any real merit to the two bank house idea?


Was this the original location of the 1-2-both switch on E35-3’s and the PO repurposed it?


I probably want to change the engine battery to AGM, or I should get a different shore power charger?


Looking forward to input!

picture 1 is the electrical diagram. Picture two is the main breaker with the 1-2-both switch and “emergency” switch on the left.
 

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Hagar2sail

Member III
Blogs Author
Thank you. It is correct on my computer but when I upload to this forum they seem to do what they want. Have to figure that out.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Theoretically if you save it to the desktop on a PC it works. Mobile devices thoroughly unpredictable. The new version will be better....
 

Hagar2sail

Member III
Blogs Author
Theoretically if you save it to the desktop on a PC it works. Mobile devices thoroughly unpredictable. The new version will be better....

Ah yes, I am almost always uploading from a mobile device.

Now on with the the real debate.....how does everyone think I should set up the boat??
 

toddster

Curator of Broken Parts
Blogs Author
There seem to be lots of different but reasonable solutions. I’m afraid I can’t read your diagram - it won’t “blow up” on my screen. For our boats with small engines, the plan that makes the most sense to me is one large battery bank for everything with an emergency reserve battery. The only reason I can think of to split the main bank is if some of the batteries are physically located separately, e.g. for weight distribution. You’d want a combining switch so that you could do work on one group without disturbing the whole system. But if yours are located together, I have no good guess.

A pretty far-fetched scenario: I believe GMDSS regulations require a separate dedicated battery for the radios. But that is only relevant to large commercial vessels. So that one could keep transmitting from the pilot house while the engine room was on fire, or some such scenario. Still, I can imagine some OCD sailor somewhere (or a ham enthusiast) wiring up a sailboat that way, to get a completely “clean” power supply for the HF radio.
 

u079721

Contributing Partner
There must be endless discussions online about how to do this, second only to which anchor holds best. But I would second the suggestion to just have one large house bank, with an emergency engine starter battery as back up. This was my system for ten years of cruising for a month each summer on the hook away from shore power. My house bank (two group 31's IIRC) had plenty of juice to start the engine, after which they would be online to be charged. I did have a battery combiner to enable charging of the starter battery without messing with the battery switch, but I found in practice that the back up didn't need charging over one month, so I usually left it disconnected.
 

markvone

Sustaining Member
Hagar,

If you can scan the battery schematic as a pdf and re-post, most will probably be able to expand it to be readable. I was able to expand the picture to get most of the details but the details just show all the limitations of having a split house bank.

I can think of only one reason to keep the house bank split and it's to avoid a single battery failure causing issues with the entire four battery house bank. I don't think this is a frequent occurrence. A better approach to avoid this I what my PO did. He added battery isolation switches like these Hellas so you can isolate individual batteries in the house bank (I have 3):

https://www.overtons.com/modperl/pr...c=Hella-Marine-Battery-Master-Switch&i=349609

The switches are small and inexpensive but require a lot more battery-size cable and a couple of buss bars to wire up. The space for the cable and buss bars isn't small.

I would hard wire all four AGMs into a single house bank use the battery switch for conventional HOUSE/START. I wouldn't worry about the isolation switches.

Mark
 
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Hagar2sail

Member III
Blogs Author
There seem to be lots of different but reasonable solutions. I’m afraid I can’t read your diagram - it won’t “blow up” on my screen. For our boats with small engines, the plan that makes the most sense to me is one large battery bank for everything with an emergency reserve battery. The only reason I can think of to split the main bank is if some of the batteries are physically located separately, e.g. for weight distribution. You’d want a combining switch so that you could do work on one group without disturbing the whole system. But if yours are located together, I have no good guess.

A pretty far-fetched scenario: I believe GMDSS regulations require a separate dedicated battery for the radios. But that is only relevant to large commercial vessels. So that one could keep transmitting from the pilot house while the engine room was on fire, or some such scenario. Still, I can imagine some OCD sailor somewhere (or a ham enthusiast) wiring up a sailboat that way, to get a completely “clean” power supply for the HF radio.

I agree. To all of my knowledge a single bank will have more life. Having two but always combining them doesn’t seem to make any sense since if you have a battery failure the whole bank goes down anyway. I would think you would have to run off of 1/2 the bank then the other half constantly switching between them if you want to maintain the redundancy. Which gives you no advantage of the larger house bank.
 

Hagar2sail

Member III
Blogs Author
Just as a double check of my understanding, currently if my house bank gets drained to under 50% and we combine the house and starting battery wouldn’t that quickly draw down the starting battery to nothing?
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
Right, the reserve battery is dedicated for starting the engine when the house bank can't. The engine then recharges the house bank.

Or at least that's how I think of it. I only use "both" for charging by the alternator, not to combine for starting.
 
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u079721

Contributing Partner
Just as a double check of my understanding, currently if my house bank gets drained to under 50% and we combine the house and starting battery wouldn’t that quickly draw down the starting battery to nothing?

In that situation I would first turn OFF the house bank, and then turn ON the back up. Now start the engine. After a few minutes (to recharge the back up) turn the house bank ON, and then the back up OFF, to charge the house bank. I can't really see a situation in which you would ever try to use both banks at once.
 

Hagar2sail

Member III
Blogs Author
In that situation I would first turn OFF the house bank, and then turn ON the back up. Now start the engine. After a few minutes (to recharge the back up) turn the house bank ON, and then the back up OFF, to charge the house bank. I can't really see a situation in which you would ever try to use both banks at once.
In the current situation since there is no ACR the only way for engine charging to get to the house bank is to have everything paralleled.
 

Hagar2sail

Member III
Blogs Author
OK, so I fixed the first attachment to be a PDF. Hopefully people can read it better now! This is my possible solution for the future state, which creates minimal rework, using much of the materials already on the boat. I need to redo some charging wiring, and get an ACR, but that is about it. It also means now the shunt is only monitoring the house bank. Eventually I would like to get a battery monitor (the shunt is from the blue seas panel installed on the boat). Good enough? A big mistake?
 

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Hagar2sail

Member III
Blogs Author
One other question, would you run the flooded cell engine battery until it quits, or just chuck it and get a AGM now?
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
My boat came with 2 deep cycle gel cell batteries in the house bank, and a single wet cell flooded start battery, not exactly what you have, but a mismatch too. This worked fine for over five years of owning the boat, at which time these batteries were over 10 years old. When they stopped working properly, I replaced all three batteries with AGM, 2 for the house bank and a single start battery.

So I would suggest you might still get a long time useage with your existing start battery, especially if you are using it mainly as a backup start battery when the house battery is run down a bit. There are enough things to spend money on in a boat, so I would keep that battery. But I'm not an expert in these things, yet.

Frank
 
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