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Old 31-05-2020, 16:26   #1
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Post House Bank OFF/1/2/BOTH switch

Hi All

We have a 12v house bank (4x6v in Series-Parallel).

It was setup by PO, and as far as I can trace the wires looks like in the picture below.

I understand why on occasion you might want to draw from the house banks separately, (OFF/1/2/BOTH switch) but I see some downsides:

1. The charging bus bar and OFF/1/2/BOTH switch is a few meters away from the batt compartment and also away my BMV712 shunt - this is a pain because the +ve sense wire is only connected to one pair of batteries.

2. I want to install a inverter - that too needs to be connected to the house bank as a whole - again this has to be somewhere after the BOTH part of the switch?

I am thinking I will change to a ON/OFF switch for house and joining the positive terminals in the battery compartment with one cable to the ON/OFF switch. Thoughts?

I am also thinking that the start batt and house are different chemistries - not sure why they share a charging bus and I will isolate motor inverter to start batt.
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Old 31-05-2020, 17:35   #2
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Re: House Bank OFF/1/2/BOTH switch

I have 3 sets of house batteries with two 1/2/both switches. Normally they all just stay connected in parallel. The switches allow me to isolate a bad set and I test each set by starting my engine couple of times a year. If the engine has trouble starting, time for new batteries. As to the inverter just feed it from the + bus (via fuse). The critical part of the E meter is the current shunt. As long as all charging and discharging is sensed by the shunt all is OK. The emeter reads ampere hours not watts so voltage is NBD.


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Old 31-05-2020, 17:46   #3
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Re: House Bank OFF/1/2/BOTH switch

Quote:
Originally Posted by Frankly View Post
I have 3 sets of house batteries with two 1/2/both switches. Normally they all just stay connected in parallel. The switches allow me to isolate a bad set and I test each set by starting my engine couple of times a year. If the engine has trouble starting, time for new batteries. As to the inverter just feed it from the + bus (via fuse). The critical part of the E meter is the current shunt. As long as all charging and discharging is sensed by the shunt all is OK. The emeter reads ampere hours not watts so voltage is NBD.


Frankly
That means that the inverter would be connected to the same charging bus bar as the alternators - would it really be able to sense battery terminal volatage from there?

It also doesnt address the battery monitor which needs to be able to sense the bank as a whole not 1 bank.
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Old 31-05-2020, 19:52   #4
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Re: House Bank OFF/1/2/BOTH switch

I have one + bus bar with starter, HO alternator, inverter, 12 v panel, solar charger, HF radio, small circuits, and fwd battery bank, all connected. All of the returns from above connect to one side of the emeter shunt and the batteries connected to the other. Works fine.

Ideally you want the high amp loads on the shortest wiring possible, but larger wire size can offset voltage drop from longer runs.


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Old 31-05-2020, 20:14   #5
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Re: House Bank OFF/1/2/BOTH switch

Everything you need to know and more is here: https://forums.sailboatowners.com/th...usings.137615/
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Old 31-05-2020, 20:49   #6
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Re: House Bank OFF/1/2/BOTH switch

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4....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.sailboatowner...d.php?t=137615

This is a newer primer for boat system wiring design with a thorough digram: Building a Good Foundation (October 2016)
http://forums.sailboatowners.com/ind.../#post-1332240

The Short Version of the 1-2-B Switch Stuff: http://c34.org/bbs/index.php/topic,5....html#msg38552 This is a link to the Electrical Systems 101 Topic, reply #2
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Old 01-06-2020, 13:32   #7
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Re: House Bank OFF/1/2/BOTH switch

I would wire the 4 house batteries in a series/parallel configuration and change the switch to a simple on/off - Blue Seas 6006 for example. Positive to charge bus from one side of the bank, negative from the other side to the shunt.

The charge bus should be for the house bank only. All charge sources (including solar) should go to it with the exception of the 65 amp alternator. It should go directly to the start battery. Once the start battery is fully charged the West Marine VSR will send the alt current to the house bank. You do not need the switch on the VSR.

The inverter positive feed connects to the charge bus. Its negative to the bus after the shunt.

This configuration does not allow you to start the engine from the house bank, which you currently cannot do either. The 1/2/both switch can be used to allow this if desired.
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