Today's Message Index:
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1. 09:24 AM - Re: Lithium Battery and Alternator Failure (Robert L. Nuckolls, III)
2. 09:28 AM - Re: Lithium Battery and Alternator Failure (Robert L. Nuckolls, III)
3. 09:48 AM - Re: Lithium Battery and Alternator Failure (Ken Ryan)
4. 11:04 AM - Re: Lithium Battery and Alternator Failure (Robert L. Nuckolls, III)
5. 12:31 PM - Rotax vacuum pad gear ratio? (rparigoris)
6. 02:04 PM - Re: Lithium Battery and Alternator Failure (Robert L. Nuckolls, III)
Message 1
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| Subject: | Re: Lithium Battery and Alternator Failure |
At 02:59 PM 10/14/2021, you wrote:
>Hi Bob,
>I've read your list and many other contributions
>for several years, and have learned a tremendous
>amount. I think this list and others of its type
>are examples of the best of the internet.
>I've had some experiences and a significant
>recent failure with a Plane Power/Hartzell
>alternator and Lithium Iron Phosphate battery
>installation which might be interesting to the community.
>I built the Carbon Cub EX over 2013-2017 using
>resources from this list and the Aeroelectric
>Connection to design and install the electrical system.
<snip>
>Operating Experience:
>Following normal starting I see 60 amp charging
>rates into the battery for about 30 seconds. The
>charge rate tapers and stabilizes under 10 amps
>over another 30 secs or so. This is usual
>behavior since new over 100's of starts. (Well
>over 500 hours on all these components). The B
>lead is protected by a 60 amp ANL fuse which has never blown.
good background
>Alternator Failure:
>About 30 flight hours ago the panel mounted
>'Alternator Out' LED became permanently
>illuminated. This lamp had flickered from time
>to time since original installation. Alternator
>behavior was normal otherwise. I contacted
>Hartzell and for initial troubleshooting,=C2 they
>chose to send me an incandescent lamp to replace
>the LED for testing purposes. I was not able to
>do that test before departing on a cross country
>trip. On this trip the field breaker popped
>during cruise flight. First time ever. I saw no
>indications of any other issues.=C2 I reset the
>breaker and the system appeared to be
>functioning normally again, except for the persistent Alt Out indication.
I'm mystified as to why you opted for
continued flight operations without
diagnosis and mitigation of an
anomalous condition . . . but that's
just me.
>Following a takeoff about 10 hours after the
>breaker had popped, the charging output remained
>over 30 amps for several minutes.
What was your bus voltage during this interval?
>I was fortunate to be at=C2 a 'big' airport and
>remained in the pattern. Alternator output then
>dropped close to zero and system voltage read ambient battery (about12.7v).
>I had to beg a bit, but mfg overnighted me a
>replacement alternator. Said they believed I
>burned it up by not running a battery management system.
Horse feathers. The only way to 'smoke' a
normally functioning alternator is to operate
it at near max rated output for extended
periods of time with INADEQUATE cooling.
Given the track record of this installation
I suspect you're not even close to over-taxing
this alternator under any condition.
>But I have a few questions:
>Does this failure mode, that the battery is 'too
>hungry' for the alternator, seem plausible?
No
>Would there be a straightforward means to
>'throttle' charging current through the B lead to 'protect' the alternator?
>My workflow since installing the new alternator
>around 15 flight hours ago has been to manually
>cycle the field (using the master switch) every
>5 seconds after start until the charging current
>stabilizes below 25 amps or so. Is this a
>reasonable procedure? Or am I just creating more unintended consequences?
>Other suggestions about how to improve this system?
Absolutely not necessary. If you're seeing the same
after-start alternator output currents as described
in your narrative, all is well with the new alternator.
>I think I am most likely heading for a
>replacement battery with a BMS. I think this
>would be ok as they seem to be more refined devices at this point.
The BMS is necessary/useful ONLY for situations where
the ship's system does not include those features
as a design goal. It's REALLY EASY to design
an system that totally negates the need for a
BMS. The BMS only adds cost and complexity to
the battery's design while adding nearly zero performance
enhancement.
Does your alternator installation include ov protection?
BMS item 1 (ov management) covered.
Is your alternator's demonstrated output within
operational limits for the battery? You've
operated this configuration for many hours and
observed no really anomalous behaviors. A high
recharge rate after cranking is expected and
normal no matter what kind of battery is
present . . . and certainly well within the
alternator's capabilities.
If your new alternator is functioning like
the old one did when new, then you're good
to go.
The only thing a BMS does that the ship's
system cannot normally do is cell charge balancing.
This is necessary only as the battery ages and
has been subjected to numerous deep cycles.
The cranking battery of a vehicle normally NEVER
sees a deep discharge. Cranking the engine
takes but a few percent of total capacity. After
that, the alternator is supposed to pick up
the loads. This is why cranking batteries often
last so long.
BTW . . . I've worked a couple issues for clients
involving alternator failures from this manufacturer.
Failures of process control . . . not design.
Your non-BMS battery, unless subjected to
a (1) sustained ov condition before your breaker
tripped or (2) numerous deep discharges is
probably just fine. Do a cap and load check on
it and drive on. Failure of a CAP check is
good reason for replacement due to one or more
cells failing. PUSHING a failing LiFePO4 is
morel likely to precipitate an in-flight battery
issue than anything else . . . a condition that
a BMS cannot fix (but might warn via serial
data busses on 'smart' designs).
P.S. There's an hangar-legend floating around out
there that blames a particular alternator failure on
replacement of a wet lead-acid with an SVLA
battery. Turns out to be a gross failure of
design in the alternator magnetics. Ergo,
a competently designed, manufactured, installed
and operated alternator is virtually bullet-proof.
Completely impervious to choice of battery
technology.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 2
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| Subject: | Re: Lithium Battery and Alternator Failure |
At 04:28 PM 10/14/2021, you wrote:
>Chris,
>Lithium batteries are great energy
>resources.=C2 However, one of its benefits can
>bite you in the "alternator".=C2 Here's how....
>The internal resistance of these batteries are
>so low that they can easily take and give huge amounts of current.
Alternator's are inherently current limited by
their magnetics. An alternator cannot open it's
own b-lead protection by 'overloading' . . . it
just won't put out that kind of current. They're
generally capable of a few percent above nameplate
rating. This number falls off as the alternator
gets hot but the battery's demand for recharge
current is not a potential hazard to any alternator
or legacy generator configuration.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 3
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| Subject: | Re: Lithium Battery and Alternator Failure |
Bob said:
"The only thing a BMS does that the ship's
system cannot normally do is cell charge balancing."
Isn't it also true that LiFePO batteries can be damaged by charging when
the battery is too cold, and that the BMS will protect against that?
On Fri, Oct 15, 2021 at 8:33 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 04:28 PM 10/14/2021, you wrote:
>
> Chris,
> Lithium batteries are great energy resources.=C3=82 However, one of its
> benefits can bite you in the "alternator".=C3=82 Here's how....
> The internal resistance of these batteries are so low that they can easil
y
> take and give huge amounts of current.
>
>
> Alternator's are inherently current limited by
> their magnetics. An alternator cannot open it's
> own b-lead protection by 'overloading' . . . it
> just won't put out that kind of current. They're
> generally capable of a few percent above nameplate
> rating. This number falls off as the alternator
> gets hot but the battery's demand for recharge
> current is not a potential hazard to any alternator
> or legacy generator configuration.
>
>
> Bob . . .
>
> Un impeachable logic: George Carlin asked, "If black boxes
> survive crashes, why don't they make the whole airplane
> out of that stuff?"
>
Message 4
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| Subject: | Re: Lithium Battery and Alternator Failure |
At 11:38 AM 10/15/2021, you wrote:
>Bob said:
>
>"The only thing a BMS does that the ship's
>=C2 system cannot normally do is cell charge balancing."
>
>Isn't it also true that LiFePO batteries can be
>damaged by charging when the battery is too
>cold, and that the BMS will protect against that?
The term 'BMS' is kinda foggy . . . some
manufacturers add a PTC current limiter
in the end of an 18650 cell and advertise
it as having a BMS.
Then there are products like True Blue for
TC aircraft where the BMS is nothing less
than a small computer with a boat-load of
duties for managing performance and risks.
One needs access to the performance specifications
of each product claiming to offer a BMS. True Blue's
devices are designed and qualified to FAA
TSO documents that specify all pertinent
operating requirements . . . requirements
easily demonstrated during qualification
testing.
So without specific documentation speaking
to management of low temperature charging
limits, one cannot assume that the feature
exists.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
Message 5
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| Subject: | Rotax vacuum pad gear ratio? |
Hi Group I have a B&C SD20S alternator on the vacuum pad of a 914. Speed is not
ideal for the SD20S, a bit too slow.
I'm looking at the parts diagram and there is a 29T vacuum pad drive gear that's
driven off of a spline on the dog hub. It drives a 22T driven gear that engages
to the vacuum pad drive sleeve.
>From the pictures it looks possible to have a larger than 29T drive gear and smaller
than 22T driven gear.
Does anyone offers such a set of gears? Thx. Ron P.
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=503539#503539
Message 6
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| Subject: | Re: Lithium Battery and Alternator Failure |
>I had to beg a bit, but mfg overnighted me a replacement alternator.
>Said they believed
>I burned it up by not running a battery management system.
I'd really like to talk to the individual who
produced this analysis . . . ESPECIALLY if he/she
is in the business of marketing alternators.
The assertion is completely without foundation
in either physics or practice.
Bob . . .
Un impeachable logic: George Carlin asked, "If black boxes
survive crashes, why don't they make the whole airplane
out of that stuff?"
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