Battery isolation/combinations

Dec 29, 2012
148
Hunter 37 Jacksonville
I have read and think I understand the basics of battery combining. However the previous owner of my 37 seems to have had a unique set up. I'm not sure how to proceed and am hoping for some guidance.

There are 2 batts under the steps, 2 under the sole, 2 under the nav station and 2 in the far aft. There is an isolator and three large cables(4 gauge) from the alternator into the batt box under the steps. 3 smaller wires(number 10) out from the batt box. One large wire out of the batt box to the floor batts, which combines to the batts under the nav station, and to the panel. One large cable to the aft batts. 2 of the smaller wires out of the batt box go to the floor batts.

I have a new 3 bank charger that is located next to the nav station. Will be installing solar panel soon.

So should I have a 'central' charging point in the batt box which has the batts separated, and has input from the alternator, batt charger, and solar?

I'm confused why there would be large cables out and smaller cables. I would assume the smaller would be for charging. But why are there also large cables out. I also assume that his plan was to separate the areas of the boat. Aft being for the cockpit, batt box for starting, and floor and nav for house. Which actually seems good to me. There is one batt switch, so I don't know how you would separate/add the other banks together, or if you would want to.

Opinions and ideas appreciated.
 

splax

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Nov 12, 2012
694
Hunter 34 Portsmouth
An accurate diagram would be a big help. Is the issue how to hook up your charger or how to configure your battery banks? Are there loads supplied by battery banks that don't go through the panel? That would explain a charging wire going to a battery bank which serves either an independent load or acts as a reserve bank in case of a catastrophic failure.
 
Dec 29, 2012
148
Hunter 37 Jacksonville
I've attached a rough diagram. It actually helped clarify the situation some for me as well. I guess I'm wanting to hook up the charger and configure the output from the alternator, and the solar. My thought was that I would want to configure those 3 output wires in the battery box for a central point for the three banks from the charger, and use the same configuration for the output from the alternator, and the solar.

Yes there are several loads that come off the banks that don't go through the panel. The autopilot and GPS run off the aft bank and the fridge and head bilge off the sole bank.

I read where the negative from the charger should be run to the last batt in the bank. Is that important? The old charger just dumped out with the positive. I think.



Thanks
 

Attachments

Feb 6, 1998
11,713
Canadian Sailcraft 36T Casco Bay, ME
I have read and think I understand the basics of battery combining. However the previous owner of my 37 seems to have had a unique set up. I'm not sure how to proceed and am hoping for some guidance.

There are 2 batts under the steps, 2 under the sole, 2 under the nav station and 2 in the far aft. There is an isolator and three large cables(4 gauge) from the alternator into the batt box under the steps. 3 smaller wires(number 10) out from the batt box. One large wire out of the batt box to the floor batts, which combines to the batts under the nav station, and to the panel. One large cable to the aft batts. 2 of the smaller wires out of the batt box go to the floor batts.

I have a new 3 bank charger that is located next to the nav station. Will be installing solar panel soon.

So should I have a 'central' charging point in the batt box which has the batts separated, and has input from the alternator, batt charger, and solar?

I'm confused why there would be large cables out and smaller cables. I would assume the smaller would be for charging. But why are there also large cables out. I also assume that his plan was to separate the areas of the boat. Aft being for the cockpit, batt box for starting, and floor and nav for house. Which actually seems good to me. There is one batt switch, so I don't know how you would separate/add the other banks together, or if you would want to.

Opinions and ideas appreciated.
After looking at this diagram all I can say is that your PO did you absolutely no favors. Best bet would be to remove it all and start fresh.


  • Lose the diode isolator and move to an Echo Charger or voltage activated combiner.


  • Make sure any banks that are separated utilize proper cross wiring so current flows through the bank evenly and the batteries remain in balance.


  • Wire the house bank as just that one large contiguous house bank


  • Wire in a starter or reserve bank


  • Decide on a switching & wiring protocol that you like eg: a 1/2/BOTH or three ON/OFF switches.


  • Are you going to do everything off the house bank or separate starting and house loads?




The unfortunate reality is that starting 100% fresh will be the easiest solution to a kludge like the PO left you with..
 
Feb 26, 2004
23,087
Catalina 34 224 Maple Bay, BC, Canada
Maine Sail's right.

Here's "The Why" & also how to do it:

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4949.msg30101.html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowners.com/showthread.php?t=137615
 
Dec 29, 2012
148
Hunter 37 Jacksonville
Thanks for all the information. So to verify your information on a couple points:

1. Take all the batteries and combine them into one bank. Rather than trying to isolate them into 2-3 banks based on their separate locations. That would actually be very easy, as there are large cables that go to all the battery locations.

2. Update the isolator.

3. It is OK to charge into the bank from the engine, charger, and solar. Without any separator mechanism.

I do want some separate start bank. But guess even just one battery separated would get that. Which would be easy. Since there is room in the battery box for 2 batteries. One could be the reserve start backup. The other could just be wired into the house bank.

I was getting mired in the complexity. But your solution is so easy, even understandable for me. Thanks again.