I flew for 6 years with two batteries (one alternator) and hauled around
the extra 16+ lbs of battery.  The only time I ever found it somewhat useful
was starting on cold mornings. I finally removed the second battery and now
simply swap out the battery ever year or two.  While it happens, alternator
failures are rare (mine is underdriven by approx 40%) and if you have a
suitable warning (big yellow light in front of my eyeballs as well as
voltage meter) of voltage abnormalities, a single battery will get you to an
airport most places.  For those of you flying in desolate wilderness, then
two batteries are a different matter.

I think you will find that almost everyone currently flying is flying with
one alternator and battery.  I have not heard of any problems with such.
The additional complexity and more belts make me question the need for two
alternators, when I  never needed the second battery. But, that is my
personal viewpoint and you need to do what makes you feel comfortable.

FWIW

Ed

Ed Anderson
RV-6A N494BW Rotary Powered
Matthews, NC
----- Original Message -----
From: "Mark Steitle" <msteitle@mail.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Tuesday, June 15, 2004 3:09 PM
Subject: [FlyRotary] Re: alternator redundancy


> Ken,
> Something to consider... a second conventional alternator adds a second
fan
> belt.  If one lets go, the second one (hopefully) will survive to continue
> spinning the water pump and alternator.  If you loose both belts at the
> same time, you will have to land asap since your coolant won't be
> circulating.  Also, these little Geo alternators are about half the weight
> of the Mazda unit, so by this rationale there isn't a weight penalty.
>
> Mark S.
>
>
>   At 06:35 PM 6/15/2004 +0000, you wrote:
> >Hi Mike,
> >I've been kicking this around for quite some time (I was a motorcycle
> >mechanic while in college).  The idea was to use a motorcycle or
> >snowmobile magneto.  The problem is that there just isn't much room on
the
> >between the flywheel and the redrive to mount the magneto components.  I
> >just recently received my 2.85 redrive from Tracy and hope to take
another
> >look at this problem this fall.  There is also a possibility of mounting
> >the magneto components on the accesory end of the engine.  More to follow
> >in the coming months; I hope someone beats me to finding a solution.
> >
> >Ken Powell
> >
> >
> > > Dear All,
> > >
> > > There was a thread a while back in which one of our colleagues
> > suggested the
> > > possibility for a second alternator perhaps mounted on the PSRU??
> > >
> > > Could be a lighter option for redundancy than two batteries
> > >
> > > Did this go anywhere?
> > >
> > > Mike
> > >
> > >
> > > >>  Homepage:  http://www.flyrotary.com/
> > > >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
> >
> > >>  Homepage:  http://www.flyrotary.com/
> > >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>
>
> >>  Homepage:  http://www.flyrotary.com/
> >>  Archive:   http://lancaironline.net/lists/flyrotary/List.html
>