Sender: <marv@lancaironline.net>
To: lml@lancaironline.net
Date: Wed, 08 Jun 2005 13:32:50 -0400
Message-ID: <redirect-988625@logan.com>
Received-SPF: none
 receiver=logan.com; client-ip=204.17.195.90; envelope-from=ted@vineyard.net
From: "Ted Stanley" <ted@vineyard.net>
Subject: Dead Batteries and Jump Starting
MIME-Version: 1.0
Content-Type: text/plain;
	charset="iso-8859-1"
Content-Transfer-Encoding: 7bit

I glanced over a number of the posts regarding a dead battery incident. I
thought pehaps you all might find some useful items out of an article I wrote
years ago (see below).

If you want to check your electrical system don't pay much attention to the
ammeter. Focus on the voltmeter. If you don't have proper system voltage with
the engine running and alternator ON then something isn't right, regardless of
whatever the ammeter indicates.

Ted Stanley - A&P-IA


"LOOK BEFORE YOU JUMP"

by Ted Stanley
Aviation Safety Counselor

Dead or weak batteries are a problem for pilots in any season.  How often have
you been all loaded up, running a little late, and you climb in the cockpit,
flip on the battery master, turn the key, and very little if anything happens?
Your first thought is, "Where can I get a jump?", right?

WRONG!!

Your first thought should be "WHY ?".  A dead or weak battery is often the cause
of an inability to start an engine, but don't stop there.

Is the alternator belt loose?  Is the battery old and weak? Are the battery
terminals corroded?  Has the voltage regulator failed?  Is the voltage regulator
improperly adjusted?  Are some of the diodes in the alternator bad resulting in
low system voltage?  Was the battery master switch left on?  As a mechanic I've
had pilots come to me with all these problems and then some.  I remember the guy
whose lead battery posts became so hot they melted as a result of high
electrical resistance between the aluminum wire and the terminals, and the one
whose battery split open from freezing because the battery sat idle and
discharged all winter (he had gotten a "jump" in Teterboro and wanted another
one upon arriving on Martha's Vineyard!).

The battery acts as a storehouse of electrical power.  It has several functions,
it provides power to start the aircraft, it serves as a reservoir of power to
run high current, non-continuous loads (landing gear motor, landing lights,
etc.), AND it serves as a source of power if the charging system should fail.  A
dead or weak battery is UNAIRWORTHY.

Picture this.  It's dusk, instrument conditions cover your route of flight.
Would you launch after a jump start with a weak battery?  Think about it.  Even
during daytime in VFR conditions, if your charging system fails you will have
only a few, very short minutes before you lose your aircraft lighting,
electrical engine gauges, fuel gauges, avionics, electrically powered landing
gear and indicator lights, your options, probably your composure, and possibly
your life.

Another thing to consider is that the charging system treats the battery just
like any other load.  A dead battery is a big load, and most things FAIL when
the load on them is highest.  Remember, a failing charging system could be the
reason the battery was weak in the first place.

An aircraft lead-acid battery is NOT like a car battery.  It is smaller and
therefore has less capacity. It's internal construction is more fragile and less
tolerant of electrical abuse.  As a battery discharges a chemical change takes
place.  When charged the process reverses.  It takes 12 to 24 hours to properly
charge a dead battery.  Don't think that you can get a "jump", sit on the ramp
for 20 minutes with the engine running, and have a fully charged battery.  It is
chemically impossible.  The battery may be charged with enough power to start
the plane but it will lack ENDURANCE.

Endurance is a function of capacity and contents.  The capacity of a battery
will diminish over its life span (normally 3 to 5 years).  It is like a car with
a fuel tank that gets smaller over the years.  The contents (amount of charge)
of a battery is equivalent to the amount of fuel in the tank.  If you have a
little fuel in your tank you can travel a few miles, your car will run fine,
have plenty of power, and everything will SEEM normal, but if all of a sudden
you have to make a long trip, you're in trouble.

A cockpit voltmeter is a very useful tool.  It can be a sort of fuel gauge in
the event of a charging system failure, as the voltage drops so do your options.
You can also tell if your battery is getting weak by checking the system voltage
prior to engine start and again while the starter motor is turning.  If your
aircraft is not equipped with one, consider buying one that plugs into the
cigarette lighter.  They are available from a variety of sources, including most
pilot shops.  Be sure not to plug a 12 volt meter into a 24 volt aircraft!

A properly calibrated voltmeter can tell you if your charging system is
maintaining the correct voltage.  System voltage should be about 14 volts for 12
volt batteries and 28 volts for 24 batteries, but check your pilot's operating
handbook or ask your mechanic to be sure.  It's actually possible to have an
indication of positive current flow on your aircraft ammeter without having the
correct system voltage to run the various aircraft systems and maintain the
battery in a proper state of charge.

Let's say you left the master switch on, what about charging the battery?  This
is best left to a mechanic, however under FAR 43.3 (g) servicing batteries is
permitted by pilots as preventative maintenance on any aircraft owned or
operated by that pilot which is not used in air carrier service.

Charging an aircraft battery is not complicated, but some special rules apply.

Remove the battery before charging.  To avoid sparks, remove the negative cable
first and install it last.  Unless the electrolyte level is below the plates,
never add water to a discharged battery.  If you do, the battery will probably
overflow because the electrolyte level rises during the charging process.  This
results in not only a mess, but an imbalance in electrolyte concentration after
the battery is charged and the level adjusted.  Be careful, battery acid can
burn your eyes and eat holes through clothing.  Neutralize spilt acid with
baking soda.  Leave the caps on the battery during charging.  The battery may
become warm, but should not get hot during charging or else the plates may warp.
The charge rate should be low, about 3 amps.  NEVER use an automotive "quick"
charger, it will damage the plates and result in premature battery failure.  The
electrolyte in the battery will normally gas (bubble or fizz slightly) during
the latter part of the charging cycle.  The gases produced, hydrogen and oxygen,
are explosive so avoid sparks by turning off the charger before disconnecting
the battery.  Once the battery starts to gas, check the specific gravity with a
hydrometer to determine the state of charge.  A fully charged battery will have
a specific gravity of about 1.265 to 1.300. After charging, the battery and
battery compartment must be clean, dry, and free of any acid residue (may appear
as a white powdery substance) prior to reinstallation.

Remember to make an airframe logbook entry as required by FAR 43.9 as to the
work you performed.  This last item is important, without it the aircraft
maintenance history is incomplete and makes it difficult for your mechanic to
maintain the aircraft in a safe condition.

Fly safely, and for happy landings remember to "Look Before You Jump".


P.S.  If you are the kind of pilot who for whatever reason seems to have trouble
remembering if the master was turned off, here's a little technique you can try.
Always leave the anti-collision light or beacon light on, at least that way when
you walk away from the plane you can plainly see whether or not everything has
been switched off.