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(no email)
Date: Thu Jun 09 2005 - 23:57:51 EDT
The function of an isolator or a combiner is to automatically isolate the
house battery from the starting battery when you turn the engine off. You
could do it by hand but the first time you forget and run both batteries
down overnight, and can't start an engine in the morning, you will
appreciate it.
The isolator has some solid state diodes that split the output from the
alternator to both banks. To install in you have to disconnect the
alternator charging output and pass it through the isolator that has one
input and two outputs. Disadvantages are 1. The isolator has a voltage
drop built in so your batteries no longer get a full charge. You can
overcome this on alternators that have an external voltage sensing wire
which can be connected directly to one of the batteries to sense the actual
voltage. 2. Being solid state, a voltage spike or overload can damage them
rapidly. 3. If one bank develops a bad cell the alternator will keep trying
to charge that battery and so the good battery will never get charged - it
is always the lowest battery that gets charged first.
The combiner achieves the same result in a different manner. You leave all
the alternator circuits as-is, connected to the starting battery. The
combiner has three leads - one to each of the positive battery terminals and
a ground. When it sees that the voltage has risen on either battery above
13.3, it connects the other battery to it so they share the charge. There
is no voltage drop so both batteries get a full charge. No charge is shared
until the starting battery gets to 13.3. If the second battery is faulty
or has too heavy a load and starts to drag the starting battery down, the
combiner will disconnect to protect the starting battery from discharge.
Combiners are slightly more expensive than isolators but much more rugged.
We've manufactured over 25,000 for West Marine. We give an UNCONDITIONAL
warranty. It doesn't matter how or when you acquired it, or what happened
to it, if you can return it we will repair/replace at no charge. Try
getting that warranty on an isolator!
There is an extensive FAQ on combiners at
http://www.yandina.com/combInfo.htm
I'm not unbiased - I invented the combiner in 1993.
Regards,
Andina Marie Foster,
----- Original Message -----
From: "Richard Goodwin" <>
To: <>
Sent: Thursday, June 09, 2005 10:33 PM
Subject: Re: lv-ab: battery isolator question
> OK, I've read this a few times, and I have to ask ...
> What exactly is a "battery isolator", and what is it
> supposed to do?
>
> Dick
>
>
>
>
> --- Lee Haefele <> wrote:
>
> > If you put one of these in, you need to relocate the
> > voltage regulator
> > "sense" wire. Many alternators do not have this
> > capability, if the
> > regulator is built in. Otherwise you get .5 to .7V
> > less at the batteries
> > and they are chronically undercharged. I don't
> > think they are necessary.
> > Lee Haefele
> > ----- Original Message -----
> >
> > Subject: lv-ab: battery isolator question
> >
> >
> > >
> > > can someone give a simple explanation of battery
> > isolators and
> > > why they are a Good Thing (TM)? also, does one
> > want an isolator
> > > for the alternator?
> > >
> > > inquiring but naive minds want to know...
> > >
> >
> >
>
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