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Old 06-07-2016, 19:30   #1
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Batteries isolated?

I have a 1983 Catalina 27. The 3 batteries are connected in a chain with all 3 positive terminals connected and the negative terminals too. It doesn't seem logical to me that the battery separator switch can isolate the starter battery. Does any one know?
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Old 06-07-2016, 19:43   #2
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Re: Batteries isolated?

You are describing batteries in " parallel " Any switch between the " bank" and a load will be isolating all 3 batteries.
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Old 06-07-2016, 22:08   #3
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Re: Batteries isolated?

Thanks - So one battery should have the + wire disconnected from the other batteries and attached to the "batt" pole on the ignition switch via the battery selector?
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Old 07-07-2016, 12:22   #4
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Re: Batteries isolated?

If you wire batteries in parallel such as yours, you get the same voltage at the end but you add up all the amp hours for extended usage. It's like having one big battery. The last positive wire coming off the group goes directly to the switch and from there off to the loads. There's plenty of images if you google it. You should also have a fuse close to the batteries before it goes off to any loads.
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Old 07-07-2016, 12:31   #5
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Re: Batteries isolated?

In order to have two banks, you will have to have two batteries in parallel connected to the switch, and the other battery by itself connected to the other bank at the switch.
Often these banks are called "house" and "Starting"
Someone connected all three into one big bank, and I can see the logic in that, but you do have to manage your batteries, just like you do your fuel supply if you only have one bank
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Old 08-07-2016, 13:42   #6
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Re: Batteries isolated?

you say you can see the logic of having all 3 batteries connected together. You think I should just leave them alone?

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Old 08-07-2016, 14:19   #7
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Re: Batteries isolated?

On our boat, Batt1 and Batt2 are connected to their respective terminals on the battery connector switch. Batt3 is connected to Batt1 through a high current continuous relay which is activated by the ignition switch. When the engine is on, Batt3 is paralleled with Batt1, and when the Ign switch is off, Batt3 is isolated. Actually, not quite this simple, since Volvo, in their infinite wisdom, dump all other loads when the key is turned to the START position.
A diode between the Start terminal and Aux terminal solved the problem.
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Old 08-07-2016, 15:28   #8
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Re: Batteries isolated?

Thanks
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