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Date: Fri, 06 Aug 2004 20:47:18 -0500
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] battery question
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kevin lane wrote:

> -Gary dunfee is a mobile x-ray tech and eaa member.  the batteries he 
> uses come in matched sets.  when one goes "bad" (performance drops) 
> the whole batch gets replaced.  Gary gives us these batteries.  he 
> claims they are the highest quality made, exceeding the odyssey 
> batteries. they are a bit heavier because of the additional plates 
> inside.  my hangar mate has at least three years and maybe 500hrs on his.
> I recently put a fresh one in my plane.  I flew it an hour and it 
> worked fine.  I was amazed at how fast the prop turned over, 
> indicating how old the prior battery had gotten.  the battery had been 
> sitting on the shelf a year maybe before I installed it.  it showed 
> about 11 1/2 volts then.
> I flew to Camarillo last week.  about 20 miles from crater lake, smack 
> in the middle of the cascade mountains, I noticed my egt's shooting up 
> 100 degrees.  I pushed the mixture to full rich, but that only 
> slowed rate.  I pulled some power and got them to start back down.  I 
> realized my rose ignition had tripped.  also I had not shut off my 
> strobe and wigwag lights.  my volt meter showed 8 volts.  I figured I 
> had lost my alternator.  I shut down everything.  I had just been 
> dropped by flight following because of radar coverage.  my wife was 
> very calm!  I was flying the t-craft version of the rv, no electrical 
> system.  I even shut off my gps since it had switched to its battery.  
> Klamath falls was less than 30 minutes.  then I noticed my voltage was 
> up to 10 volts.  interesting.  I decided to shoot for Carson city and 
> save my 8500' of altitude.  a bit later I saw 11 1/2 volts.  thank god 
> I kept the altitude.  at one point Ellen say "there's an airport below 
> us".  yeah, RNO, ceiling 8400'.  so much for my off and on gps 
> technique.  voltage was showing 13 1/2 volts now.  I tried turning 
> things back on, and there seemed to be no problems.  we got gas at 
> Carson city, lunch at minde, and flew to Camarillo, no problems.  I 
> wasn't able to talk with anyone about this and flew back, 6 hrs, with 
> no problems, 13 1/2 volts the whole time.
> so, is it possible the battery had a charge that wore off and then 
> went into some deep charge mode, overloading my little nippondenso 
> alternator?  the most amps I ever saw was 20 while it was trying to 
> get back to the 13 volt mark.  maybe leaving my lights on was too 
> much?  has this problem fixed itself, or do I need to pull the 
> alternator and battery to have them tested?  I used to pretty much 
> ignore the volt meter while flying.  not anymore.
> Kevin Lane  Portland, OR
> e-mail-> n3773@comcast.net <mailto:n3773@comcast.net>
> web-> http://home.comcast.net/~n3773 <http://home.comcast.net/%7En3773>
> (browse w/ internet explorer)

Did you bring everything back on line during that flight, including 
lights? If you left the lights off, that's a pretty large % of total 
load in a vfr a/c. One possibility is that the alternator has lost one 
or more of the diodes that convert AC to DC. That can limit its ability 
to charge at its rated capacity. I've got an old truck that had just 
those symptoms: ran fine & panel mounted volt meter read around 12 V 
until I drove at night. Then the battery would go down within 20-30 
miles of driving to the point that I couldn't restart the truck after 
shutdown.

New alt. cured it.

Gonna make it to Rotary Roundup this year?

Charlie