nuckollsr(at)cox.net
Guest
|
 Posted: Sat Jan 06, 2007 10:00 pm Post subject: Another 60A alternator, internally regulated voltage reg |
 |
|
At 08:56 PM 1/5/2007 +0000, you wrote:
| Quote: | It was an Odyssey pc680 and it's van's 60 amp alternator with the internal
voltage regulator. I don't know for sure the make but many say it's a
nippondenso (ND). I didn't take it off yet.
Yes, the voltage is monitored all the time by my EIS & EFIS and there's a
pretty tight voltage range which would trigger an "alarm" if it went out
of range. It never did prior to just oughtright dropping a couple of
volts permanently. But it was my original battery which I abused
throughout the build process and I'm not the least bit surprised. I got
my 4 years money's worth as far as the battery goes....
|
Okay, so this battery's failure is not necessarily attributable
to any operating conditions in the airplane.
| Quote: |
No, I didn't actively track the battery's voltage becuase I ALWAYS left it
on a trickle charger while hangared at the home airport and it never gave
me any grief during long trips like to Oshkosh plus the alarm range was
pretty tight on the EFIS (I guess you could say that's gross tracking to
some extent). My bus voltage once the engine is running has always been
about 14.2 volts plus or minus .1
|
That's about what I would expect.
| Quote: |
I had heard that a "weak" battery can damage the alternator/regulator so
this seamed to have validated that statement. For sure though, from my
observations, the battery appeared to go bad first then 2 hours later
after a new battery was installed the regulator seems to have failed.
|
I'm skeptical of such claims. Consider how many batteries
you've replaced in cars without having to replace the alternator
too.
I've "killed" a few alternators in various test situations
but all failures involved either loss of cooling or mechanical
issues such as bearing or shear-shaft failures.
The way to "test" a weak-battery-kills-alternators hypothesis is
to separate the two components and then craft a test plan designed
to kill an alternator. In other words, if I had a brand new
alternator and a charter to damage it in some way on the test
stand, what kinds of abuses might I heap upon the unsuspecting
device to bring about its untimely demise?
Once such a test plan is devised, then deduce how battery
behavior mimics any of the abuses you've crafted for the
purpose of killing an alternator.
I'd be interested in anyone's ideas as to how you might go
about it. Alternators are inherently self current limiting.
Given sufficient cooling air, you cannot "overload" one to
destruction. Alternator diodes are robust and will withstand
reverse voltage transients many times greater than system voltage.
It's the regulators that are most vulnerable to a load-dump
event and that's been demonstrated by several builders using
Van's (and perhaps other) alternators combined with b-lead
contactor controls.
I'm not suggesting that battery condition might not be a bit-player
in a scenario that's hard on alternators. For example:
I can see how the "weak battery" thing might have morphed into
a cause/effect for alternator failure where someone knows that
having a battery be disconnected from the alternator at the same
time all loads are removed causes a potentially hazardous
over-shoot. One might deduce that a "weak" battery has
lost its ability to mitigate a load-dump events thereby
placing the alternator at-risk.
If this hypothesis were in play for your situation, the alternator
seems most likely to have failed while the "weak" battery was
in place. Certainly having a "strong" new battery in place totally
eliminates the risk for hazardous transients during ordinary
system load reductions.
This could be hypothetically thrashed for days but without very
specific test data, we'll never know how your tandem failures
may or may not have been related.
| Quote: | My current battery voltage is really good, even after the voltage
regulator failure stress on the battery.
|
The momentary abuses heaped on your battery were of limited duration
and will have the net effect of reducing your battery's service
life by some small fraction. By the way, once your alternator is
turned ON after engine start, are you able to turn it OFF from
the pilot's controls while the engine is running?
Bob . . .
| | - The Matronics AeroElectric-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?AeroElectric-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
