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28-10-2014, 06:59
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#1
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Registered User
Join Date: Sep 2008
Location: New Orleans, LA
Boat: Catalina 30 Tall Rig
Posts: 234
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Two Banks Connected at Negative Terminals
Good morning, everyone. I am gradually getting to know the systems on my newly purchased 1980 Catalina 30, one weekend at a time. I am well researched in 12V systems but am quite the novice in application. This weekend I was changing out the batteries (The boat has what I thought was two single battery banks). When I was replacing the batteries I noticed that although each battery's positive cable led to their respective post on the 1/2/both/off switch, battery two's negative cable was wired to battery one's negative terminal. Is this just a shortcut to closing each battery's circuit as the positives are independently wired to the switch? That is my first instinct but wanted to defer to the 12V sages here. Thanks!
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28-10-2014, 07:28
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#2
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,082
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Re: Two Banks Connected at Negative Terminals
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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28-10-2014, 07:46
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#3
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Registered User
Join Date: Sep 2008
Location: New Orleans, LA
Boat: Catalina 30 Tall Rig
Posts: 234
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Re: Two Banks Connected at Negative Terminals
Thank you! My assumption was that with only two batteries in total, it was wired this way in lieu of using a neg bus bar. When it comes to electronics (as with anything I can't see or touch) I only minimally trust my own assumptions.
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28-10-2014, 07:46
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#4
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Registered User
Join Date: Feb 2013
Location: Southern California
Posts: 588
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Re: Two Banks Connected at Negative Terminals
I suspect that there is a cable connecting those two negative terminals to a common ground.
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28-10-2014, 08:48
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#5
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Registered User
Join Date: Sep 2008
Location: New Orleans, LA
Boat: Catalina 30 Tall Rig
Posts: 234
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Re: Two Banks Connected at Negative Terminals
Quote:
Originally Posted by ryon
I suspect that there is a cable connecting those two negative terminals to a common ground.
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There is!
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28-10-2014, 09:09
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#6
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Registered User
Join Date: Dec 2012
Location: the Netherlands
Boat: Wibo 1100 36 ft
Posts: 66
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Re: Two Banks Connected at Negative Terminals
Quote:
Originally Posted by NOLA_sailing
Is this just a shortcut to closing each battery's circuit as the positives are independently wired to the switch?
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Yes it is.
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29-10-2014, 08:22
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#7
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Registered User
Join Date: Sep 2014
Posts: 413
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Re: Two Banks Connected at Negative Terminals
totally correct installation, battery negatives wire together then you have one lead to the ground on the hull, engine block, zinc ect all part if the bonding system,
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29-10-2014, 09:37
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#8
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Registered User
Join Date: Dec 2008
Location: SC
Boat: None,build the one shown of glass, had many from 6' to 48'.
Posts: 10,208
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Re: Two Banks Connected at Negative Terminals
Quote:
Originally Posted by NOLA_sailing
Good morning, everyone. I am gradually getting to know the systems on my newly purchased 1980 Catalina 30, one weekend at a time. I am well researched in 12V systems but am quite the novice in application. This weekend I was changing out the batteries (The boat has what I thought was two single battery banks). When I was replacing the batteries I noticed that although each battery's positive cable led to their respective post on the 1/2/both/off switch, battery two's negative cable was wired to battery one's negative terminal. Is this just a shortcut to closing each battery's circuit as the positives are independently wired to the switch? That is my first instinct but wanted to defer to the 12V sages here. Thanks!
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Your good if I understand you. Neg. to neg. terminal and one wire to the neg. buss. If I did? A book on DC fundamentals would be a great investment. Nothing is as a frustration as DC in a saltwater environment.
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29-10-2014, 10:07
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#9
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Registered User
Join Date: Sep 2014
Location: New London, NH
Boat: Intrepid 9 meter, 29.5 feet
Posts: 91
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Re: Two Banks Connected at Negative Terminals
It might help to think about when the battery switch is on "both". The switch connects the positive terminals, but there has also got to be a negative connection of the two batteries, if they are to work together in parallel.
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29-10-2014, 10:18
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#10
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Registered User
Join Date: Jan 2011
Location: Cowichan Bay, BC (Maple Bay Marina)
Posts: 9,703
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Re: Two Banks Connected at Negative Terminals
Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams
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)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com
Yes, the negatives are connected and go back to the engine ground.
These links are to show the the positive side options. You need to understand both of them.
Good luck. Happy learning.
__________________
Stu Jackson
Catalina 34 #224 (1986) C34IA Secretary
Cowichan Bay, BC, SR/FK, M25, Rocna 10 (22#) (NZ model)
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29-10-2014, 10:21
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#11
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Registered User
Join Date: Jan 2008
Location: Kingston, ON
Boat: Albin Vega 27'
Posts: 530
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Re: Two Banks Connected at Negative Terminals
NOLA
I have found these two links most helpful.
Electrical Systems 101
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com
Have a read through each of these, they are gold when it comes to understanding electrical systems in small boats. I had a very good understanding of automotive electrical systems but ran into issues when I tried to apply them to a boat. I gained quite a bit more insight about marine electrical systems from these posts and other marine electrical literature.
Also you will find lots of more helpful posts here from these two generous people and many others.
__________________
Glenn
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29-10-2014, 10:23
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#12
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Registered User
Join Date: Jan 2008
Location: Kingston, ON
Boat: Albin Vega 27'
Posts: 530
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Re: Two Banks Connected at Negative Terminals
Stu your very helpful and quick too.
__________________
Glenn
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29-10-2014, 10:24
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#13
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Registered User
Join Date: Sep 2008
Location: New Orleans, LA
Boat: Catalina 30 Tall Rig
Posts: 234
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Re: Two Banks Connected at Negative Terminals
Quote:
Originally Posted by Stu Jackson
Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: Basic Battery Wiring Diagrams
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)
1/BOTH/2/OFF Switches Thoughts & Musings - SailboatOwners.com
Yes, the negatives are connected and go back to the engine ground.
These links are to show the the positive side options. You need to understand both of them.
Good luck. Happy learning.
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Thank you, Stu! I have seen (and bookmarked) this and other Main Sails musings that are very informative. The real world wiring just threw me off as most diagrams show negative leads from separate banks joining at a neg bus. After thinking about it, and with confirmation from the CF brain trust, I now understand that the neg terminal is acting as a neg bus.
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29-10-2014, 10:26
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#14
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Registered User
Join Date: Sep 2008
Location: New Orleans, LA
Boat: Catalina 30 Tall Rig
Posts: 234
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Re: Two Banks Connected at Negative Terminals
Thanks, Glenn and Swampy!
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29-10-2014, 10:49
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#15
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Registered User
Join Date: Apr 2013
Location: So Cal
Boat: Catalina 387
Posts: 967
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Re: Two Banks Connected at Negative Terminals
I don't know the age of your C30, but catalina definitely didn't put any busses at all in mine. The factory wiring was poor, then the siliconehead POs seemed to have no idea at all how to hook wires together. My "neg buss" at the panel was about 20 wires crimped, soldered, and taped together.
Needless to say when I rewired I put in bussbars - one for the negs up in the panel, and a large one under the chart table for the batteries. I have 3 batteries (one under the starboard settee) and it cleaned up the wiring quite a bit.
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