Today's Message Index:
----------------------
1. 09:48 AM - battery boil/overheat (Owen Baker)
2. 08:05 PM - Re: Boiling batteries (Robert L. Nuckolls, III)
3. 08:16 PM - Re: battery boil/overheat (Robert L. Nuckolls, III)
4. 09:27 PM - Re: Z12 Alternator Amps (RV7ASask)
Message 1
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| Subject: | battery boil/overheat |
7/7/2012
Hello Ed, This posting from the aeroelectric-list archives may be of
interest:
Match: #10
Message: #48521
Date: Feb 19, 2010
From: "Robert L. Nuckolls, III"
<nuckolls.bob(at)aeroelectric.com>
Subject: Re: B&C Regulators and water-falls
=98OC=99 Baker
Time: 07:45:33 AM PST US
From: "Ed Anderson" <eanderson@carolina.rr.com>
Subject: Re: Battery only time -AeroElectric-List: Z-19RB clarification
I certainly agree, Bob. A clear case of a where my design focused on a
very
low probability occurrence (boiling battery) ending up almost assuring
that
at some point that switch would get in the incorrect position and cause
a
problem.
In fact, has anybody on the list EVER experienced or have first hand
knowledge of someone who had a battery boil/overheat due to run away
(over
voltage) alternator??
Ed
Message 2
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| Subject: | Re: Boiling batteries |
At 09:44 AM 7/6/2012, you wrote:
<eanderson@carolina.rr.com>
I certainly agree, Bob. A clear case of a where my design focused on
a very low probability occurrence (boiling battery) ending up almost
assuring that at some point that switch would get in the incorrect
position and cause a problem.
In fact, has anybody on the list EVER experienced or have first hand
knowledge of someone who had a battery boil/overheat due to run away
(over voltage) alternator??
There are many such cases over the 100 year history
of aircraft . . . or the hundreds of millions of
other vehicles with DC power systems. Spectacular
events in aviation, like spectacular events elsewhere,
get lots of attention mostly because they are rare
. . . and spectacular to boot.
The ship's alternator is a significant source of
energy often rated at 60 amps or more and virtually
boundless for voltage during a runaway condition
unless (1) shut down in a timely manner or (2) held
in a state of current limit by ship's loads + plus
what ever the battery is able to accept.
RG/SE/SVLA/AGM style batteries offer the most
benign responses to OV abuse of any technology.
They contain so little liquid that steam-driven
events are non-existent. There have been some explosions
of liberated H2-O2 mixtures when batteries were
boxed up in an airtight container along with an
ignition source. But for the most part, the most
severely abused batteries will produce failures
such as these . . .
http://tinyurl.com/cgjoheo
http://tinyurl.com/blt9x3l
http://tinyurl.com/ckbes36
http://tinyurl.com/bn2wd67
http://tinyurl.com/82azaht
http://tinyurl.com/88lhd4n
The OV event is an immediate hazard to electro-whizzies
with damage taking place in tens to hundreds of milliseconds.
Batteries take much longer. In fact, during the first few
milliseconds of an OV condition, the battery will "throw itself
into the line-of-fire" to forestall rate of rise in bus
voltage until the ov protection system (automatic or
manual) has time to react.
Battery failures due to over-charge are very slow events
taking tens of minutes to hours to manifest. An airplane
fitted with a capable OV protection system will never
suffer such an event.
Bob . . .
Message 3
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| Subject: | Re: battery boil/overheat |
At 11:44 AM 7/7/2012, you wrote:
7/7/2012
Hello Ed, This posting from the aeroelectric-list archives may be of interest:
Match: #10
Message: #48521
From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>
Subject:
Re: B&C Regulators and water-falls
OC Baker
I'd forgotten about that one. I searched without success for a
discussion on a Glasair battery box explosion. An RG battery
suffered an extended OV condition within a tight battery box
and apparently out-gassed to an ignition source within the box.
The box blew up and scattered pieces into the tail cone but
the engine was magneto sparked and continued to fly. The
pilot got it back on the ground and was able to tell the
tale.
The modern alternator in an airplane, like a big gun
in a battle, can be an essential component of survival.
But unleashed in unintended circumstances it can be a
substantial hazard too. FAST ov protection is a requirement
in TC aircraft . . . for rare but compelling reasons.
--------------------
FAR23.1351(c) Generating System. There must be at least one
generator/alternator if
the electrical system supplies power to load circuits essential for safe
operation. In addition--
(1) Each generator/alternator must be able to deliver its continuous rated
power, or such power as is limited by its regulation system.
(2) Generator/alternator voltage control equipment must be able to
dependably regulate the generator/alternator output within rated limits.
(3) Automatic means must be provided to prevent damage to any generator/
alternator and adverse effects on the airplane electrical system due to
reverse current. A means must also be provided to disconnect each generator/
alternator from the battery and other generators/alternators.
(4) There must be a means to give immediate warning to the flight crew of a
failure of any generator/alternator.
(5) Each generator/alternator must have an overvoltage control designed and
installed to prevent damage to the electrical system, or to equipment
supplied by the electrical system that could result if that generator/
alternator were to develop an overvoltage condition.
Bob . . .
Message 4
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| Subject: | Re: Z12 Alternator Amps |
I went flying today and did an Aux alternator check as you suggested Bob. After
turning most of the electrical load off, once again I was left with 8 amps and
14.4 volts on the Main Alternator.
Cruising at 2400 RPM I selected the Main Alternator Off. Voltage dropped to 12.9
and the Aux Alternator came on line with a steady 12.9 volts. The amps then
slowly climbed up to and settled down at 20 amps, more than double the reading
of the Main? To the best of my knowledge everything is wired correctly.
Any suggestions?
Regards
David Lamb
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=377590#377590
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