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klehman(at)albedo.net
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 Posted: Sun Jan 07, 2007 7:54 am Post subject: Another 60A alternator, internally regulated voltage re |
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For years I was skeptical too that a weak battery would hasten
alternator death. However eventually I developed a few thoughts on why
there may be some truth to this in automobiles.
1. Higher longer charging does tend to make the alternator run hotter
and some internal VR alternators are not well cooled. Any vehicle that
is started with jumper cables is about to ask for a serious effort from
its charging system.
2. Installing a new but partly charged battery may stress the alternator
even higher than ever as it charges the battery at max current for an
extended period. An old alternator just may not be up to the effort.
Maybe the brushes are worn or maybe the solid state devices get hotter
than they have for awhile. Certainly the cooling of old greasy/dirty
components is not as good as on a clean new unit. I'm not sure that a
test stand is going to successfully imitate the service environment that
I'm thinking of. This might explain death shortly after the new battery
is installed though.
3. Weak "maintenance free" batteries are sometimes low on electrolyte. I
think that further reduces their capacity to absorb any excess voltage
or current and might lead to more voltage excursions. Most people never
pop the caps off automobile batteries any more as it is often not
obvious how to do it, or that it can be done. It seems that my little
(8AH) AGM batteries will accept very little current initially when fully
discharged.
4. As a WAG another contribution might be abnormal operation while
fooling around with a weak battery. If I leave the ignition/key on with
my ND IR alternator on my aircraft without starting the engine, the
alternator does draw several amps of field current and it will heat up
quite noticeably with no cooling airflow.
Anyway my personal rule now is to change out any suspicious battery with
a new FULLY charged unit and I can sometimes send the vehicle to the
wreckers with the original alternator. I do run weak batteries in my
tractor but that has an external homemade VR that hangs out in the
breeze (like the alternator) and everything runs very very cool 
Ken
| Quote: | > SNIP>
> 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.
> 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 . . .
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luckymacy(at)comcast.net
Guest
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| Posted: Mon Jan 08, 2007 10:13 am Post subject: Another 60A alternator, internally regulated voltage re |
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My update. I bought an alternator from Autozone that matched the suzuki/chevrolet automobile replacement alternator often quoted to be the same as Van's 60 amp internally regulated alternator even though the part number was just slightly different. I could not tell a difference from the outside though their computer said 55 amp and not 60 amp. It has a Nippondenso internal fan and a hotline of 800 228 9672.
In the install manual, it has a CAUTION: A defective or discharged battery can damage your new alternator.
But the reason my alternator may have failed is that there was one of the feet on the alternator was cracked clean through. Though it was still rigidly mounted that had to set up some fun vibration within the alternator itself. Don't know if that actually was a cause for the battery to fail as opposed to the opposite hypothesis I was banting about.
Fun stuff. I still have the magic alternator killing odyssey pc680 battery I removed if anyone has a Van's 60amp alternator they want to test for kill.....
Next task is to replace the high intensify landing/taxi light bulbs that burned out when turned on with 18 volts on the bus....
lucky
[quote]-------------- Original message --------------
From: Ken <klehman(at)albedo.net>
| Quote: | --> AeroElectric-List message posted by: Ken
For years I was skeptical too that a weak battery would hasten
alternator death. However eventually I developed a few thoughts on why
there may be some truth to this in automobiles.
1. Higher longer charging does tend to make the alternator run hotter
and some internal VR alternators are not well cooled. Any vehicle that
is started with jumper cables is about to ask for a serious effort from
its charging system.
2. Installing a new but partly charged battery may stress the alternator
even higher than ever as it charges the battery at max current for an
extended period. An old alternator just may not be up to the ef fort.
Maybe the brushes are worn or maybe the solid state devices get hotter
than they have for awhile. Certainly the cooling of old greasy/dirty
components is not as good as on a clean new unit. I'm not sure that a
test stand is going to successfully imitate the service environment that
I'm thinking of. This might explain death shortly after the new battery
is installed though.
3. Weak "maintenance free" batteries are sometimes low on electrolyte. I
think that further reduces their capacity to absorb any excess voltage
or current and might lead to more voltage excursions. Most people never
pop the caps off automobile batteries any more as it is often not
obvious how to do it, or that it can be done. It seems that my little
(8AH) AGM batteries will accept very little current initially when fully
discharged.
4. As a WAG another contrib ution might be abnormal operation while
fooling around with a weak battery. If I leave the ignition/key on with
my ND IR alternator on my aircraft without starting the engine, the
alternator does draw several amps of field current and it will heat up
quite noticeably with no cooling airflow.
Anyway my personal rule now is to change out any suspicious battery with
a new FULLY charged unit and I can sometimes send the vehicle to the
wreckers with the original alternator. I do run weak batteries in my
tractor but that has an external homemade VR that hangs out in the
breeze (like the alternator) and everything runs very very cool
Ken
>> SNIP>
>> 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?
|
| Quote: | >
> 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
& gt; > in a scenario that's hard on alternators. For example:
|
[quote] > 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 d ays bu [quote][b]
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