Date: Wed, 3 Aug 2016 18:52:56 -0700
Reply-To: Brett Ne <brettn777@GMAIL.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Brett Ne <brettn777@GMAIL.COM>
Subject: Re: testing capacity of house battery
In-Reply-To: <CABToOYJ0qc-NTX28RosOOjYLqfaH6VDW7YwtU1Z65=0GBi=owQ@mail.gmail.com>
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I wouldn't go monkeying with a boost converter. The stock system, when
working properly, does a decent job of charging both batteries. If your
house battery isn't charging well, then there is a problem somewhere in the
system. The boost converter will only mask the problem and adds in another
possible failure point. Is it possible for this thing to fail and put out
80v as a result? I dunno. I would focus on analyzing and fixing the
system.
I would first test the alternator to make sure that it is putting out a
good voltage under load with the house battery disconnected from the
system. I saw an email just a couple days ago about this on this
listserve. If the alternator checks out healthy, reconnect the house
battery & compare the charging voltage at the car battery to the voltages
into & out of the relay and at the house battery terminal. Those voltages
should all be pretty close & a significant discrepancy will point out what
item needs attention.
I have a Riviera and they came with the Surepower isolator. I really like
it, but I don't think that there's any fancy voltage boosting circuitry in
it; just basically some heavily heatsinked diodes for the isolation and a
feedback signal to the alternator to boost voltage enough to compensate for
the voltage drop caused by the diodes.
Standard automotive batteries only last 4-5 years, and you say that this
battery is a few years old, so it's probably getting towards the end of
it's lifespan. They are designed to put out a high current for a few
seconds, and then be immediately recharged. Used as a house battery, they
face long periods of time in a state of partial discharge, which is not
healthy for them. The house battery on Albert is going on 5 years, and
it's capacity is much lower than it was the first couple of years; I'll be
getting a new one before next summer.
Also, if you're running the fridge while driving, that puts a big load on
the alternator, especially if the headlights are on, and slows the rate of
recharging the batteries while driving.
Brett
--
Brett in Portland, OR
"Albert" '82 VanaFox I4 Riviera
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