Date:         Tue, 4 Apr 1995 09:29:26 -0700 (PDT)
Sender:       Vanagon Mailing List <vanagon@vanagon.com>
From:         David Schwarze <schwarze@superc.nosc.mil>
Subject:      Re: Suggestions for installing Home Stereo in '73 Bus

Mark Hamilton writes:
> 
> I need some suggestions as to what type of batteries, inverter (if
> necessary), charger, etc. to buy to install my home stereo in my bus.  It
> includes a 100W amp driving Bose AM-5 (satellite) speakers and a CD changer
> as well as a dual tape deck.  I would want to go 5 days between charges
> using the stereo up to 8 hrs. a day while travelling (if possible).  It
> would also be nice to run a small 110 volt accessory (like a rice cooker)
> now and then without worry of overly depleting the charge.
> 
> Also, is there a way to install an in-line charger that diverts excess
> charge from the starter battery to RV or Marine batteries?
> 
> I've checked out the archives in great depth and done outside research but
> still can't figure out the best arrangement.  I need someone's opinion who's
> done something like this before.  

That would be me.  :)

What you need to do is find out what your stereo draws (in watts) when you
have it cranked.  I would do this not by looking at the ratings on the
back of the components, but by putting a meter in line with the power
cord (need an analog meter to do this, or one with a "max" reading) and
measuring the actual current drawn.  Then you need to go out and buy an
inverter that will handle the power.  Judging by your system, I would say
you will need at least a 200 watt inverter.  Last time I tried this, it
worked okay, but there was a "buzzing" noise, produced by the inverter
which was kind of annoying.  You might be able to filter it out with a
noise filter, but I'm not sure.  It also might not be a problem if you
buy a high-quality frequency controlled inverter, but I can't say for
sure.  Just make sure you can return the inverter if it doesn't work
out.  Oh, and if you have it cranked, you probably won't hear the buzz :).

As far as batteries, you will have to have a hell of a lot of batteries
to go for 5 days (40 hrs * ~20 amps = 800 amp hours!).  Figure on spending
$250 on four golf cart batteries (that would get you about 400 amp hours)
and then you only get maybe 3 days worth.  If you don't have the stereo
cranked all 8 hours every day, you might get 5 days worth.  :)

You can get a heavy duty relay (I think that's what Derek Drew calls it)
to connect the golf cart batteries to your main battery while driving,
but you would have to drive for at least 12 hours to recharge four dead
golf cart batteries this way.  The other option is to camp at a KOA
once a week and plug into their AC.  For this you would need a ~50 amp
power supply, that's about another hundred bucks.  I think Sears has
a 2/10/50 type charger that would work, for under $100.

SO, you have:

Batteries		$240
Inverter	    >=	$150
Charger		    >=  $80

Total			$470 + misc. (relay, noise filter, etc.)

-David

=============================================================================
David Schwarze                  '73 VW Safare Custom Camper (Da Boat)
SAIC Comsystems                 '73 Capri GT 2800 (Da Beast)
San Diego, California           '87 Mustang Lx 5.0 (Da Bruiser?  Soon...)
schwarze@nosc.mil                http://papaya.nosc.mil/~schwarze
=============================================================================