Date:         Sat, 18 Sep 2004 19:09:47 -0600
Reply-To:     Gnarlodious <gnarlodious@EARTHLINK.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Gnarlodious <gnarlodious@EARTHLINK.NET>
Subject:      Re: dual battery isolator
In-Reply-To:  <JBEOJOBKGBDBEAIBOCBEIEDKDJAA.syncrowestytd@mindspring.com>
Content-type: text/plain; charset="US-ASCII"

Entity Dennis Haynes spoke thus:

From 23 Aug 2004

> after they get warm the actual voltage drop is closer to 1.1 volt.
Well, I just installed the Hellroaring model BIC-95150B and I am dismayed to
se a 1.4 volt drop across the switch at ambient temperature.

At $174.45 for the high technology and much touted product this is
disappointing. The specs page didn't mention voltage drop. I'll try to
communicate with them about it during the week, maybe it's a defect.

-- Gnarlie


 At 90 amps, the isolater is dissapating almost 100 watts. This is why they
need heat sinks. You are paying for this power. Now, with this voltage drop,
you are getting less than 13 volts to the batteries and accessories. Ok, so
now you can modify the regulator to increase the voltage or use a remote
sense wire to compensate. At full load the limiting factor of an alternators
capacity is its own resistance. Thus at full load, it is only slightly more
than 50% efficient. Yes, 1/2 the power produced is given off as heat in the
alternator itself. That is why they have a big fan and they still get hot.
So, we increase the voltage of the alternator by 1.1 volt so at 90 amps the
alternator dissipates an additional 100 watts of heat. Can we say shorter
life? So at full load, we are wasting ~200 watts of power due to the use of
the isolator. Under ideal conditions, 1 HP = 746 watts. Not that you will
notice but we are wasting .26 HP here. The big issue here is the load on the
alternator.