First, thank You to everybody that responded about the fire
extinguisher, the alternator (and the master switch), and about my
granddaughter and her R22!!!
I am still troubled by the (apparently) accepted practice of the master
switch not killing everything. I want my KR2 to behave like my Warrior
II - When I dump the master (split switch), I want the panel dead as a
doornail. Off is off. This is an emergency procedure item, and the
last thing I need to be dealing with in a situation like that is having
to go kill each rocker switch. Not good. So I am going to retain some
kind of alternator "slaved" arrangement to the master. If the master is
off, the airplane electrical systems are off. Period.
My typical charging voltage is in the 14.5 to 15.0 volt range, although
I have seen it sneak up a bit higher if it is really cold outside. The
accepted convention for charging most car/air/lawn/solar batteries is in
the range of 13.8 to around 15.0, give or take. At anything above 13.8,
you are in the gassing area for the battery, so you don't want to stay
there if the battery is full. On solar systems, it isn't unusual to see
voltages in the 15+ range, but this is typically with a smart
controller, and it will drop the voltage and amperage as soon as it
detects the battery bank maintaining voltage when it checks.
A good place to get good information is Deltran
("http://batterytender.com";), makers of the Battery Tender. Their smart
tenders are 4-stage, and their web site explains more than most people
want to know about battery charging!
For Jim Morehead, N522PC, I have several thoughts and suggestions:
1. Check the regulator. My Revmaster isn't running nearly that hot.
Checking the regulator on something like this is a challenge, because
you can't run to AutoZone and try a replacement. But at least check the
wiring, etc. Also, the output of the alternator is almost pure AC.
There isn't any significant filtering on the Revmaster system (it uses
the battery as a filter capacitor), and the AC component can wreak havoc
with cheaper DC voltmeters. With the engine running at 3,000 or so,
switch your voltmeter to AC and see what it says. I'm betting you will
see a very troublesome amount of AC on your supposed DC buss, especially
if you have a failing battery! If you study the workings of the typical
tachometer (Westach) for a Revmaster, you will discover that it is
actually an AC voltmeter. I don't like it, but it is what it is. With
the master switch off, but the panel still connected to the alternator,
you are hitting your avionics with something between 25 and 40 volts AC.
2. Check your battery. Sounds basic, but they can fool you. The 2006
battery I pulled from the KR2 will float at about 13.6, and shows a full
charge after just minutes on the charger. At a supposed "full charge",
it will crank the engine for about 5 seconds. The identical model
replacement I installed will float at 12.3 or so, and it takes hours for
the charger to back-off. So it could be that you have something as
simple as a dying battery.
3. 16.5 volts is over the practical limit for most avionics and typical
"12 volt" electronics. The accepted number is 15.9 volts. You could
"safety" each electronic item by inserting a power diode in series, but
that doesn't really address the over-voltage situation with the
alternator/regulator.
4. If you can't pin down what's going on, there are a couple of things
you could do. One would be to install a power diode in series with the
alternator output. This should be a diode in the 50-100 amp. range,
with heatsink. That will drop the output by about 0.7 volts, and that
might get you back into the green - about 15.5 volts, which is still too
hot, long-term. If you look at battery combiners, dual-battery
adapters, etc., you will find what you're after - most of these items
have two huge diodes on a heatsink. Each diode will get you a 0.7 volt
drop. An accepted practice in the power electronics industry is
something called a crowbar. Brute force, in other words. You could
install a power zener between the fuse/circuit breaker and across the
associated load, to ground. Get something like a 15.5 volt zener. As I
said, this is brute force. If the voltage goes too high, the zener will
conduct and pop the fuse or throw the breaker. I don't like this
approach much, as it leaves you with a dead panel item in-flight, but it
*will* save the item!
5. If you have firewall space, you might consider installing a huge
capacitor across the alternator output. It won't lower the voltage, but
it will filter a good chunk of the AC component, and also slow down any
spikes and other critters that can destroy avionics.
Finally, Thank You to those that appreciated what Randi is doing with
her R22! I am so proud of her that sometimes it is hard to write about
it! Her instructor critiques her with a very detailed "report card"
after each flight. Our standing arrangement is that if she gets a "A"
or "B", she gets the dinner of her choice. Dennis is a seriously 'hard'
instructor, so I figured this would be a safe arrangement! What is
wonderful (???) is that I owe her 14 dinners at the moment, and I've
been buying them as fast as I can, hence I only owe her 14 more right
now! Sigh!!! At $300/hr in the R22 and $600/hr in the R44, you'd think
that would be enough spending for one day!!! I started in 6th grade,
and she's going to be a carbon copy of that! No wonder progress on the
KR2 is so slow!
And I keep forgetting to mention: Our KR2 camera is at
"hangar.from-mi.com:82" The login is "admin", no password. You might
want to use Firefox if IE gives you problems. The camera is remotely
steerable.
Best to everybody,
Dave.
