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Seeking feedback or validation on DC design

Jan 9, 2020
25
J Boat J/42 1 New Castle NH
New to this forum with a new to me boat since Nov. My old C&C had much simpler systems, so I'm just looking for some feedback on the DC wiring I think I have finally figured out on this new boat. Enclosing my poor man's schematic for reference, but basically looking to confirm that Bat #3, which is not connected the battery switch, and only connected to the bus, is essentially isolated. I think my plan is to connect #3 to the #1/#2 bank, effectively making it a three battery bank. That would give me a 315 aH bank on SW-1 and allow me to use a single solar panel/charge controller for on mooring battery charging. So just curious if there are any flaws in that logic, or any other ideas or concerns about the wiring in general. note... I added the sterling charger myself recently, mostly based off the info from Main Sails's how to site.. such a valuable resource. Thx for the feedback!
 

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Oct 19, 2017
6,312
O'Day 19 Littleton, NH
Welcome aboard, wsconner. It's good to be the first to greet a fellow NH resident. You have definately shown sound thinking by posting your question here, among the wealth of expertise that SBO members have to offer.
Sadly, I am of little help here, while I've had several classes in electronics through the years, I have little actual experience outside of wiring my own house. No experience with the kind of equipment and problems found on a boat.
Since I know others will be along shortly to straighten it all out, I don't mind adding my perspective. Maybe my own questions will get answered.
In your schematic, I don't see a ground. Perhaps that is assumed at the main panel or at the charger. The other thing I see is a closed circuit on your batteries #1-3, but I suppose the charger keeps that open so your batteries don't short, I don't really know how these things work. Marine electronics is something I have yet to get involved in. I plan on adding electric to my boat, but it will be a while 'till I get there.
In the mean time, I'm certain you will get good advice here.

-Will (Dragonfly)
 
May 17, 2004
2,510
Beneteau Oceanis 37 LE Havre de Grace
By connecting the galley battery to the bus you are putting it in parallel with #1 and #2, so yes you'll be able to charge them all simultaneously from the same source. I do have a few other questions/concerns though:
- Are all of the positive leads from the battery fused appropriately? That includes the ones that go to the charger, windlass, bus, and switch.
- As drawn you won't generally be charging the start battery except from the Sterling charger. The only way around that is to manually switch the 1/2/B switch to Both while the engine is running, then remember to switch it back to 1 when you stop if you're going to run down the house bank.
- The house and start bank are different chemistries (AGM vs flooded), which complicates charging them from the same source.

It would probably be better to match the chemistries of all the batteries and use an ACR to separate the starter bank from the house. That way the start battery would be charged properly and not need manual switching.
 
Feb 6, 1998
11,227
Canadian Sailcraft 36T Casco Bay, ME
New to this forum with a new to me boat since Nov. My old C&C had much simpler systems, so I'm just looking for some feedback on the DC wiring I think I have finally figured out on this new boat. Enclosing my poor man's schematic for reference, but basically looking to confirm that Bat #3, which is not connected the battery switch, and only connected to the bus, is essentially isolated. I think my plan is to connect #3 to the #1/#2 bank, effectively making it a three battery bank. That would give me a 315 aH bank on SW-1 and allow me to use a single solar panel/charge controller for on mooring battery charging. So just curious if there are any flaws in that logic, or any other ideas or concerns about the wiring in general. note... I added the sterling charger myself recently, mostly based off the info from Main Sails's how to site.. such a valuable resource. Thx for the feedback!
Please send me a PM with your phone number...
 
Jan 9, 2020
25
J Boat J/42 1 New Castle NH
Thanks for quick reply. Realized I hadn't provided enough context in my diagram. When I installed the sterling charger I made sure the positive cables to each battery are fused near the post (50amp). Sterling tech said that the mix of AGM wouldn't present an issue and I have a custom charging profile set to 14.7 which is ideal for the Northstars and the same general setting for the flooded. Not a lot of good info from prior owners, but I found a sticky note that described the "BOTH" setting on bat switch, says the way to charge the starter batteryis to have the switch to BOTH when running engine. Your idea sounds like a better way to integrate the starter into the entire system. As for a ground, all battery negative cables are connected to the negative bus, which is connected to the boat bonding system (not shown in schematic--will fix).

If I add Bat 3 to the parallel bank of 1&2, then I think I can eliminate one of the leads from the AC charger, as Sterling confirmed that a bank in parallel only needs one feed. Anyone done that?
Thanks so much...
 
Oct 19, 2017
6,312
O'Day 19 Littleton, NH
Wsconner, I highly recommend taking Maine Sail up on his offer. You will benefit enormously.

-Will (Dragonfly)
 
May 17, 2004
2,510
Beneteau Oceanis 37 LE Havre de Grace
If I add Bat 3 to the parallel bank of 1&2, then I think I can eliminate one of the leads from the AC charger, as Sterling confirmed that a bank in parallel only needs one feed. Anyone done that?
Thanks so much...
Yeah, I think that’s right, though I remember reading somewhere Maine Sail saying something about tying the outputs together. I’m sure, as Will said, he’d be very helpful to talk to.
 
Jan 9, 2020
25
J Boat J/42 1 New Castle NH
Funny how it seems the older you get the smaller the word becomes. So many fun times beating around the woods and waters of NH! Still think Live Free or Die is the better state motto :)

As expected, great advice from MS. Need to figure a few things on the boat, but I'll make sure I update this forum on my next steps and progress. Thanks for all the feedback and advice.
 
May 17, 2004
2,510
Beneteau Oceanis 37 LE Havre de Grace
I'll make sure I update this forum on my next steps and progress.
Yes please! I’m sure we will all learn from the evolution of your first iteration diagram to the future Maine Sail inspired one.
 
Jan 9, 2020
25
J Boat J/42 1 New Castle NH
Been meaning to send an update out. MS was kind enough to send me a simpler diagram that outlined his recommendations. I also thoroughly reviewed the post in the musings section on battery switch configurations lcoated here So between the two, I think I have a much better understanding of the principles involved and how it works. I'm enclosing another version of my working diagrams. The first slide is where I started a few weeks ago, the second slide is MS's diagram, and the third depicts how I adapted his recommendations. I'm not completely done implementing these on the boat, but now I have a solid plan to make my configuration much simpler. So many thanks to this group, MS and hopefully this give someone else a jump start when they need it.
 

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May 17, 2004
2,510
Beneteau Oceanis 37 LE Havre de Grace
Thanks for the follow up. I am a little confused about a couple points in your updated diagram:

- You seem to show the output of the 1/2/B switch as going back to the start battery, and the #2 feed as going out to the panel. I think you have those swapped. I’d think MS’s version of that switch layout provides more flexibility.

- I presume you’ll have the shunt inline between the bus and the battery negative post, where it can accurately measure all current to/from the battery, right?
 
Jan 9, 2020
25
J Boat J/42 1 New Castle NH
Yes, on the shunt. This new boat had some other stuff installed at one point - inverter, LINK2000, etc- but it was removed. As for the switch wiring, I think my diagram is mis-leading. One of the things I learned about my "GUEST" house switch, is that the labels on the front don't match the poles on the back. So in my case, the "2" position on the SW is actually the "feed or common", which is why I show it going to the DC main. I should fix that.. it is confusing. Should also point out that the yellow circle "STR SW" is not the ignition switch, it's just another simple On/Off bat switch that is connected to the starting battery.
 
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Oct 22, 2014
12,336
CAL 35 Cruiser Portland OR, moored EVERETT WA
Looking at your revised diagram it appears still in progress.

Care in wiring the “echo” ACR unit. Your connections are not following MS’s wiring. The ACR has 3 + red leads and 1 - black lead. Red leads (2 of them) pass the charging current from the positive bar to the positive battery lead of the starter battery.

The third red lead (positive) and the black (negative) lead are the starter isolation circuit. The red lead goes to the start button and the black lead is attached to the negative bus bar. This is based on you using a BlueSea SI-ACR. The SI stands for "Start Interruption". Blue Sea Systems SI-ACR Automatic Charging Relay w/Optional Start Isolation automatically combines batteries during charging, isolates batteries when discharging and when starting engines.

It appears in your diagram, that you are not following this connection structure.
 
Jan 9, 2020
25
J Boat J/42 1 New Castle NH
Thanks.. yes, I didn't depict the start interrupting wiring. Still trying to figure out how to do that. If I understand it correctly, it's an optional wiring for the SI unit?
 
Oct 22, 2014
12,336
CAL 35 Cruiser Portland OR, moored EVERETT WA
Yes. The circuit is the ground wire and the red connection to the starter.