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Old 04-08-2018, 17:05   #1
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Battery Isolator

Two separate banks of house batteries.
Want to use Isolator to keep them separated.
Was told not to hook up charger or alternator to Isolator as they would not get proper reading from battery; and equipment could be ruined.
Any thoughts on this?
Thanks
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Old 04-08-2018, 17:40   #2
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Re: Battery Isolator

Battery isolators are diodes. A diode has a voltage drop across it of roughly .6 volts. A diode is like a one way valve for electricity. A voltage sense wire on the input side of a diode will never sense the battery voltage. It will only sense the output voltage of the alternator.

If you have a smart regulator that is separate from the alternator with a voltage sense wire it can be attached directly to the battery. The regulator will then sense the voltage properly and also compensate for the voltage drop from the isolator.

An alternative that has been available for many years now is an automatic charge relay or "combiner". Anytime the combiner senses a voltage from a charging source it will combine the two battery banks. When the charging source stops the batteries will separate.

I prefer the combiner method and have had one installed for about 20 years. They are easier to install and will support all charging sources, rather than just the alternator.
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Old 04-08-2018, 19:21   #3
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Re: Battery Isolator

Poor design to split the House bank, shorter lifespan and lower total capacity. Have you got some compelling reason?

All charge sources go direct to Primary, then an ACR / VSR / combiner connects to the Reserve / Starter whatever, only when charge is active.

Sized to handle max current + margin as you would an inverter.
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Old 05-08-2018, 04:31   #4
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Re: Battery Isolator

Thanks.
Split because banks are of different vintage.
Both good but do not want to mix newer with older.
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Old 05-08-2018, 06:04   #5
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Re: Battery Isolator

Quote:
Originally Posted by CaptFigmo View Post
Thanks.
Split because banks are of different vintage.
Both good but do not want to mix newer with older.
Fair enough. When you need to replace batteries, you may want to read some of the previous threads on the logic for using one large house bank rather than two smaller ones. There are a lot of advantages to one large bank.

Also, I agree wholeheartedly with the suggestion to use a battery combiner rather than a diode battery isolator. I installed a Blue Seas ACR on our boat several years ago and it has been trouble free.

Cheers!

Steve
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Old 05-08-2018, 06:38   #6
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Re: Battery Isolator

Thanks
Have read pros and cons.
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