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Old 03-04-2019, 14:19   #1
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Eliminating the 1-2-Both-Off Battery Switch

I need your help to scrutinize and delicately provide your insights.

I will finally start the work to eliminate the "normal" battery switch and replace it with 2 on-off switches (SW1 & SW2 below) as per MaineSail's recommendations.
Please check the diagram with with the 3 scenarios and let me know if this would work plus any comments or precautions.
The reserve bank is exactly that, not to be used unless necessary.
Starting the engine and everything else will be done using the house bank. Basically this is what I have been doing for the past 2 years using the 1-2 both switch but I need validation before I change to the new circuit.

Note: The alternator and battery capacities are not important and I'll be fusing all circuits, I just need comments on the wiring.
To enlarge the diagram, click on it then click again.
Thanks in advance.
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Old 03-04-2019, 14:42   #2
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Re: Eliminating the 1-2-Both-Off Battery Switch

Wiring looks like it will do what you stated you want. The alternator will always see a battery, that's good - won't fry the alternator due to an incorrect switch setting.

I don't like to run the panel/house loads on the same battery/wire that will see the starter motor loads - doing so introduces low- and hi-voltage conditions as the starter motor is energized/denergized. I would make your 'reserve' battery the engine-start battery by wiring it direct to the starter (or thru an on/off battery switch if you'd like), wire your panel to the house battery, and have a switch that will enable paralleling the house with reserve to energize the starter from the house. Keep the ACR trickle-over charger going from the house to the reserve.

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Old 03-04-2019, 15:25   #3
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Re: Eliminating the 1-2-Both-Off Battery Switch

not sure why you have 2/0 from + bus to starter when its only supplied by 4awg, defeats the purpose. Same going from your alt back, 2/0 for alt charging? long run or huge alt? Also you may end up damaging sensitive electronics when starting. IMO i'd isolate both circuits and actually use the 'reserve' bank as a dedicated start battery with the option to isolate each bank independently for starting and reserve. I believe this is exactly what MS suggests.
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Old 03-04-2019, 15:36   #4
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Re: Eliminating the 1-2-Both-Off Battery Switch

Looking at it more you're not really eliminating the switch just complicating the install. Keep the switch and wire you alt directly to you house bank (fused). That with the arc you cant burn out you alt and depending on your alt and regulator setup might be able to get accurate voltage drop sensing and compensation.
IMO the engine start circuit should be isolated from your house loads under normal conditions (no cabin lights dimming when starting), but switched to run VHF/NAV equip etc in the event the house bank fails.
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Old 03-04-2019, 15:56   #5
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Re: Eliminating the 1-2-Both-Off Battery Switch

An interlock switch can be used to prevent starting with the house bank in the off position.
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Old 03-04-2019, 16:24   #6
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Re: Eliminating the 1-2-Both-Off Battery Switch

Quote:
Originally Posted by SVTatia View Post
I need your help to scrutinize and delicately provide your insights.

I will finally start the work to eliminate the "normal" battery switch and replace it with 2 on-off switches (SW1 & SW2 below) as per MaineSail's recommendations.
Please check the diagram with with the 3 scenarios and let me know if this would work plus any comments or precautions.
The reserve bank is exactly that, not to be used unless necessary.
Starting the engine and everything else will be done using the house bank. Basically this is what I have been doing for the past 2 years using the 1-2 both switch but I need validation before I change to the new circuit.

Note: The alternator and battery capacities are not important and I'll be fusing all circuits, I just need comments on the wiring.
To enlarge the diagram, click on it then click again.
Thanks in advance.
Personally I can't see what you are trying to achieve, replacing one rotary switch that has the capability to connect one, both or the other batteries with two switches. I have to ask, why.
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Old 03-04-2019, 16:49   #7
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Re: Eliminating the 1-2-Both-Off Battery Switch

Quote:
Originally Posted by SVTatia View Post
I need your help to scrutinize and delicately provide your insights.

I will finally start the work to eliminate the "normal" battery switch and replace it with 2 on-off switches (SW1 & SW2 below) as per MaineSail's recommendations.
Please check the diagram with with the 3 scenarios and let me know if this would work plus any comments or precautions.
The reserve bank is exactly that, not to be used unless necessary.
Starting the engine and everything else will be done using the house bank. Basically this is what I have been doing for the past 2 years using the 1-2 both switch but I need validation before I change to the new circuit.

Note: The alternator and battery capacities are not important and I'll be fusing all circuits, I just need comments on the wiring.
To enlarge the diagram, click on it then click again.
Thanks in advance.
I've completely rewired 3 boats, so I have a pretty good grasp. That said, I have no clue from your drawings what you are attempting to do.

IMHO, I would dedicate one bank - the biggest one - to the house, then isolate whatever systems you run regularly to that. I would separate the second 'bank' as one battery, and strictly use it to start your engine. Get rid of the ACR, and in its place create a bridge between the two banks using a 200A continuous service solenoid, with the contacts wired to the engine switch, such that, when the engine is running, everything is charging. The rest of the time you are running off the house bank.

Now you don't have to switch anything. Your start battery is isolated and used just for starting the engine, and your house battery services your regular needs.

I have no idea why you would ever want to run one bank down, then switch to the only one you have left that will start your engine.

And if you want a cross-over back-up, install another 200A solenoid on a helm switch to connect the two batteries together the event you over crank your starter battery and need more power.
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Old 03-04-2019, 17:41   #8
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Re: Eliminating the 1-2-Both-Off Battery Switch

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Originally Posted by CptCrunchie View Post
I've completely rewired 3 boats, so I have a pretty good grasp. That said, I have no clue from your drawings what you are attempting to do.

IMHO, I would dedicate one bank - the biggest one - to the house, then isolate whatever systems you run regularly to that. I would separate the second 'bank' as one battery, and strictly use it to start your engine. Get rid of the ACR, and in its place create a bridge between the two banks using a 200A continuous service solenoid, with the contacts wired to the engine switch, such that, when the engine is running, everything is charging. The rest of the time you are running off the house bank.

Now you don't have to switch anything. Your start battery is isolated and used just for starting the engine, and your house battery services your regular needs.

I have no idea why you would ever want to run one bank down, then switch to the only one you have left that will start your engine.

And if you want a cross-over back-up, install another 200A solenoid on a helm switch to connect the two batteries together the event you over crank your starter battery and need more power.
The arc will do what the selonoid does more or less up to 100 amps (I think itís 100) with simpler install and he already has it. I canít see more than 100 amp output alt from this setup more like 50. Agree with the reasoning behind this mod.
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Old 03-04-2019, 19:54   #9
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Re: Eliminating the 1-2-Both-Off Battery Switch

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Originally Posted by beetle View Post
...I don't like to run the panel/house loads on the same battery/wire that will see the starter motor loads - doing so introduces low- and hi-voltage conditions as the starter motor is energized/denergized. I would make your 'reserve' battery the engine-start battery by wiring it direct to the starter (or thru an on/off battery switch if you'd like), wire your panel to the house battery, and have a switch that will enable paralleling the house with reserve to energize the starter from the house. Keep the ACR trickle-over charger going from the house to the reserve.

- rob
Good point. I thought that scenario #3 would mitigate the spike risks, and I was trying to do without a 3rd switch, but you are right, and after reading further MS post (here), he suggests exactly that... I'll wire the starter to the "reserve" and have a third switch.
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Old 03-04-2019, 19:56   #10
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Re: Eliminating the 1-2-Both-Off Battery Switch

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not sure why you have 2/0 from + bus to starter when its only supplied by 4awg, defeats the purpose. Same going from your alt back, 2/0 for alt charging? long run or huge alt? ...
Long run. The batteries are very close to the switches and panel, but much farther from the starter/alternator.
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Old 03-04-2019, 19:56   #11
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Re: Eliminating the 1-2-Both-Off Battery Switch

I don't see any reason to replace the 1,2,off switch with that setup. you end up with the exact same thing but more complicated to use. with no advantages that I see.

you are still always powering both the house or engine from the same battery. or from both, exacty what the 1,2,all does but while making sense looking at it.

the main reason of removing the 1,2,all would be to have the engine battery start the engine and the house battery power the house. which you are not doing.


and in scene 2. if the house battery is totally dead, the alt may not start up and charge anything. depends if internal or ext reg and where it draws it's power from
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Old 03-04-2019, 20:04   #12
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Re: Eliminating the 1-2-Both-Off Battery Switch

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Personally I can't see what you are trying to achieve, replacing one rotary switch that has the capability to connect one, both or the other batteries with two switches. I have to ask, why.
The swicth is original to the boat (1967) it is huge and starting to get a bit "cranky". I will not replace it or buy another 1-2-both-off swicth.

Please read this article, long and very informative.
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Old 03-04-2019, 20:21   #13
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Re: Eliminating the 1-2-Both-Off Battery Switch

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The swicth is original to the boat (1967) it is huge and starting to get a bit "cranky". I will not replace it or buy another 1-2-both-off swicth.

Please read this article, long and very informative.
Yes I have read that article before and the take away for me is the repeated comment about the boat owners lack of understanding in the use of this simple tool. Understand the onboard systems and simple errors will not be a problem.
From what I can see you are planning on replacing this one simple switch with three single throw switches which still allows the same operator error, or possibly greater opportunity for error, than the original.
When redoing mine I opted for two 1-2-both switches, one for engine power selection, one for house power selection, each able to draw from either bank. With the addition of a VSR that is enabled only when the engine is running it works reliably and is very simple to understand and operate.
Works for me and others.
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Old 03-04-2019, 20:31   #14
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Re: Eliminating the 1-2-Both-Off Battery Switch

Another problem with this setup is that you'll never know if your"reserve" has enough juice or able to deliver enough amps to crank your engine .

I have two house batteries and an engine (and only engine) battery. A charge relay fills the engine battery first making sure that's always tolled up before it goes to the bank.
The shore power charger charge each battery individually.
The house batteries are deep cycle while the engine battery is high peak current.

This way I know I can always start even if I leave the light on. If the engine battery is dead but house is full I'm sure I can device a 1 ft jumper cable to get it going, not a scenario I need to optimize for.


This seems to be all in one solution, and it's prewired so you don't have make those hard to bend short cables yourself: https://www.amazon.com/BEP-Square-Ba.../dp/B0184S2S5Y
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Old 03-04-2019, 20:36   #15
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Re: Eliminating the 1-2-Both-Off Battery Switch

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Originally Posted by Uncle Bob View Post
Personally I can't see what you are trying to achieve, replacing one rotary switch that has the capability to connect one, both or the other batteries with two switches. I have to ask, why.
Quote:
Originally Posted by Uncle Bob View Post
Yes I have read that article before and the take away for me is the repeated comment about the boat owners lack of understanding in the use of this simple tool. Understand the onboard systems and simple errors will not be a problem.
From what I can see you are planning on replacing this one simple switch with three single throw switches which still allows the same operator error, or possibly greater opportunity for error, than the original.....
Well, not quite. With this scheme, when getting on the boat turn the house switch on (SW1). When leaving the boat turn SW1 off. Thats is it always...and as simple as that.
The handles for SW2 and now SW3 will be off the switch until necessary in an emergency.
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