Today's Message Index:
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1. 05:13 AM - Re: Alternator/regulator (Gary Burdett)
2. 05:59 AM - Re: Power Generation without Battery? (Robert L. Nuckolls, III)
3. 12:01 PM - Re: Power Generation without Battery? (ChrisM)
Message 1
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Subject: | Re: Alternator/regulator |
Bob,
Thanks for the clarification . I think I jumped to confusion.
Sent from my iPad
> On Jan 20, 2015, at 8:08 AM, Robert L. Nuckolls, III <nuckolls.bob@aeroelectric.com>
wrote:
>
>
> At 15:34 2015-01-19, you wrote:
>>
>> I have a JD/yanmar PM alternator and regulator with crowbar circuit. Voltage
was starting to run over 15 volts at cruise rpms. Replaced battery and regulator,
now hits 15.5 volts at anything over 2400 rpms on first test with a fully
charged battery..????
>
>
> Regulator is not properly adjusted for maintaining
> a lead-acid battery. Unfortunately, most of the
> off-the-shelf regulators for pm alternators do not
> offer user adjustments.
>
> Finding a drop-in replacement with friendlier
> performance is about your only option. Your
> problem is not uncommon and the folks who design,
> manufacture and market these products seem oblivious
> to the disservice they impose on their customers.
>
>
> Bob . . .
>
>
>
>
Message 2
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Subject: | Re: Power Generation without Battery? |
At 16:49 2015-01-19, you wrote:
Bob,
I am building a Carbon Cub - a lightweight experimental design for
backcountry use. It will use a fully electrically dependent Lycoming
engine. I plan on 1 battery/2 alternators, and I desire the system to
run the engine with any 1 of those 3 failed.
Under what scenario do you perceive that a battery
becomes unavailable to you?
I want to use a lithium battery for starting purposes only. I am not
worried about battery only endurance with 2 other power sources.
Okay . . .
Alternator technology is mature, but Li batteries seem to be still
evolving. Some type of battery fault would seem be a likely failure
mode in my planned system. (I'd like to monitor battery temp using a
probe and my on board electronics, and to have some way to
electrically isolate or even physically remove the battery).
I plan to use your Z12 or Z13 architecture.
Which #2 alternator are you considering?
People I speak with advise me that alternators (even the SD8) are
dependent on a functioning battery in the system, and that they will
cease to function if the battery fails or is taken offline.
Not true. Once they are up and running, all alternators
will continue to run self-excited unless 'stalled' by
a LARGE load, like 200W landing light or an electro-
hydraulic pump motor. The SD-8 can be installed to
self-excite (See Z figures). Many alternators on
Lycoming engines will self excite due to their
high operating speeds with the popular pulley
ratios.
Recent revelations regarding the Challenger/Aerovoltz scenario aside,
there seem to still be legitimate issues with the current Li crop. At
the very least they remain relatively unproven.
It's not one 'crop' but a garden . . . albeit
infested with some weeds. The type
certificated lithium products like True Blue
have 'full up' battery management systems that
are quite capable of preventing events like that
which plagued the Challenger owner. Further,
had the Challenger owner availed himself of
the knowledge and experience freely offered
from the pages of this List and DOZENS of
other sources, he would have caught the mis
behaving rectifier-regulator before it became
antagonistic to his battery.
I'm working on the 'frosting' article to a
series I did in Kitplanes on lithium batteries.
A major feature of the article points out
the constellation of design and marketing
approaches for lithium cranking batteries
in particular and consumer off-the-shelf
cells in general.
It will also discuss the range of offerings
for 'battery management systems' which can
range from a simple fuse built into one
end of a cell . . . up to a bucket full of
electronics and software that costs nearly
as much as the battery itself!
So I am concerned about the Li battery being a single point of
failure capable of stopping the engine.
Engine stoppage due to failed battery? Not
if you take the time to understand how all
those bits and pieces fit together to solve
your particular puzzle. If you want to
go lithium, go EarthX (Full up BMS). There
are some up-n-comers nipping at EarthX's
heels . . .
How can I design around this problem?
Simple . . . not necessarily easy but simple.
Hang out here. Read. Ask questions (which
are already under way . . . good for you!).
When you hear/read/observe some bit of
information from other sources, bring them
here to the List for sharing/sifting of
the simple-ideas in physics that define
REAL performance and risks.
Share your thoughts about load analysis,
qualify your "plan-b" to deal with failures.
Your misgivings are real but I suggest
they are borne more of ignorance than of physical
limits to performance of products that are
thoughtfully and skillfully crafted.
It's your ability to recognize those skills
that will carry you forward with confidence.
By the way, your 'advisors' who speak of
alternator/battery relationships might enjoy
joining us here too . . . their advise is
dated and/or inaccurate.
Bob . . .
Message 3
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Subject: | Re: Power Generation without Battery? |
Bob,
I think the most likely battery failure modes would be temperature related due
mild overcharging/cell imbalance/high ambient temperatures. I think I'll be pretty
protected from a runaway thermal overload due to frank over voltage as I
will use your Z figures with overload protection/notification. An internal short
may also be more likely with lithium than with lead acid.
Regarding alternator #2: I request your advice. Running the engine with the EFII
requires 10 amps - mostly for electric fuel pump. I think I need perhaps 15
amps for a comfort margin and to run the radio. Output curve vs rpm is significant
considering fuel and ignition function are at stake. But this is a vfr aircraft
and I can navigate and fly with nothing but the engine running.
So the SD8 does not have adequate output.
Perhaps adapting one of B&C's larger units intended for Continentals? Wind my
own? Hopefully something off the shelf though!
I contacted B&C on the self/persistent excitation issue and was advised that the
SD8 requires a battery in the system to operate the regulator. He referred me
to you. Also called Plane Power as it seemed their internally regulated design
should be able to continue to run following removal of external battery power,
but was advised not. Answers may have been tainted by my emphasis about actually
keep the engine running!
I don't think I have any large loads in the plane which would tend to stun the
self-excited alternator. Think I may make a small placard to remind about being
gentle with manipulations if running under such circumstances.
I believe you drew Z12 and Z13 prior to predominance of 100% electrically dependent
engines. They both show a magneto in the system for example.
Do you feel these Z figures are appropriate for adapting to electrically dependent
engines using a lead acid battery?
Do you think Z12/13 are reasonable for use with a current technology (eg EarthX)
Li battery?
Which Z do you favor and why?
If yes, is there some means to enhance the alternators propensity to continue to
produce power following battery failure?
What do you recommend for a first and second alternator for my system? Minimum
output needed is 15 amps at perhaps 1800 engine rpm. Weight is a factor for my
setup.
Thank you very much for helping me understand how all these bits and pieces do
fit together.
Your willingness to offer your expertise and experience answering questions like
these is very generous.
Chris M
--------
ChrisM
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http://forums.matronics.com/viewtopic.php?p=437421#437421
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