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Three Questions on Z-07

 
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markfw



Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

PostPosted: Wed Mar 13, 2019 4:01 pm    Post subject: Three Questions on Z-07 Reply with quote

I am building an electrically dependent LSA Carbon Cub. I will be using the SDS EFI system. I am currently planning to use Z-07 as the basis for my electrical system architecture.

I have three questions:

1. Using Z-07 as drawn my Endurance Bus (E-Bus) load is only 4.0 amps, due to high efficiency avionics, and my MOTIVE Power Distribution Bus (MPDB) load is 14 amps due to the EFI. In an alternator-out situation if I run the MPDB on one battery and the E-Bus on the other, wouldn’t I be “wasting” some of the E-Bus battery since its load is so much less than the load on the MPDB? Assuming that I want to keep the batteries the same size, would it be better to merge the MPDB and the E-Bus, keeping all connections the same? In the alternator-out scenario I would then shut down my MAIN Power Distribution Bus to shed load and drive the E-Bus with both batteries, perhaps through a single relay.

In an earlier e-mail Bob said

Quote:
During that discussion, we concocted the idea
of an ENDURANCE bus to (1) power a
minimally useful equipment list, (2) power
additional items easily turned off to shed
load and (3) have a battery energy path
around a de-energized battery contactor.


Essentially it seems to me that with an EFI the whole MPDB could be treated as part of the E-Bus. I realize that I may be missing something here.

2. I have been looking at using a pair of EarthX ETX680 (PC680-equivalent) LiFePO4 batteries since they have a BMS that will post info to my GRT EFIS about their condition. I would like to use both batteries for starting as in Z-07. I have read that people like to separate their avionics bus from the starting battery because of a potential voltage drop during starting. However, the BMS on the EarthX batteries takes their output to zero if it drops below either 12.8v or 11.5v (both are stated in their on-line documentation). Since the EarthX batteries can demonstrably start Lycoming 4 cylinder engines without dropping off line, does this in fact imply that there is not a voltage drop below 11.5v on starting with them? Is this a difference between LiFePO4 batteries and lead acid batteries?

3. Can someone tell me what the DSS2XC61-01A is? Is it a diode?

Thanks.

Mark[/quote]


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JohnInReno



Joined: 08 Sep 2007
Posts: 150

PostPosted: Wed Mar 13, 2019 4:34 pm    Post subject: Three Questions on Z-07 Reply with quote

I have a couple of years experience with the EarthX batteries and I have
some positive comments:

1.    The voltage should not drop during the engine start unless there
is a dead stall.

2.    In a single battery installation, the battery is sized to the
alternator output. A 70 amp alternator should have an EarthX900. I would
ask EarthX about 2 batteries.

3.    I almost tested the BMS by leaving some electronics on for 2 days.
The voltage dropped to just under 12 volts and it still had no trouble
starting the engine. However, in that circumstance the battery absorbed
60+ amps for at least 15 minutes. No harm done but if it happens again I
will put it on the charger for a more leisurely charge rate.

john

On 3/13/2019 5:02 PM, markfw wrote:
Quote:


I am building an electrically dependent LSA Carbon Cub. I will be using the SDS EFI system. I am currently planning to use Z-07 as the basis for my electrical system architecture.

I have three questions:
2. I have been looking at using a pair of EarthX ETX680 (PC680-equivalent) LiFePO4 batteries since they have a BMS that will post info to my GRT EFIS about their condition. I would like to use both batteries for starting as in Z-07. I have read that people like to separate their avionics bus from the starting battery because of a potential voltage drop during starting. However, the BMS on the EarthX batteries takes their output to zero if it drops below either 12.8v or 11.5v (both are stated in their on-line documentation). Since the EarthX batteries can demonstrably start Lycoming 4 cylinder engines without dropping off line, does this in fact imply that there is not a voltage drop below 11.5v on starting with them? Is this a difference between LiFePO4 batteries and lead acid batteries?

Mark



Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=488059#488059

[/quote]


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markfw



Joined: 28 Feb 2019
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Location: Seattle, WA

PostPosted: Wed Mar 13, 2019 4:45 pm    Post subject: Re: Three Questions on Z-07 Reply with quote

thank you John. Very useful information. I will talk to EarthX about dual batteries.

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user9253



Joined: 28 Mar 2008
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Location: Riley TWP Michigan

PostPosted: Wed Mar 13, 2019 6:47 pm    Post subject: Re: Three Questions on Z-07 Reply with quote

Electronic parts frequently become obsolete and are replaced by improved versions.
Search Mouser for part number DSS2x61-01A.
At the expected engine load, the diode will drop about 0.7 volts or less and could get hot consuming 10 watts of power.
Mount it to a heatsink using heat conductive paste.


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PostPosted: Thu Mar 14, 2019 2:31 am    Post subject: Three Questions on Z-07 Reply with quote

As Joe said, electronic parts frequently go obsolete; however, "improved versions" aren't always improved. That's one reason companies keep engineers and quality control people around. I remember once when Vishay obsoleted a part and replaced it with another part. We looked at it and finally told our Air Force customer that the replacement part wasn't exactly an improved version. The Air Force talked to the Vishay manufacturing engineer and got him to change the company's plans to obsolete the capacitor. I wasn't sure what they said to him, but our defense department can pack a wallop, especially since Vishay was in Beersheba, Israel. I went there once with the quality manager to inspect their processes and that's when we got the real story. I can't say publicly what the reason was, but it had something to do with shekels. I do remember three of our engineers allowing a similar change without alerting our customer and working with them to accommodate it. When the AF found out, it wasn't long before they were walked out the company door and possibly ostracized at other defense department contractors. I haven't seen any of them since except one, and he started a company pouring concrete in our booming local commercial and residential industry. It isn't exactly high tech, but he's making the big pesos.

For this application, though, Joe is correct in all statements below. I particularly like the heat sink/conductive paste statement as temperature beyond rating is a killer on electronics. I see heat sinks used widely in today's products, especially since miniaturization has become the norm, but power dissipation (not consumption) remains high.
Henador Titzoff




On Wednesday, March 13, 2019, 11:02:36 PM EDT, user9253 <fransew(at)gmail.com> wrote:




--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

Electronic parts frequently become obsolete and are replaced by improved versions.

Search Mouser for part number DSS2x61-01A.

At the expected engine load, the diode will drop about 0.7 volts or less and could get hot consuming 10 watts of power.

Mount it to a heatsink using heat conductive paste.

--------

Joe Gores


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PostPosted: Fri Mar 15, 2019 4:36 am    Post subject: Three Questions on Z-07 Reply with quote

At 07:45 PM 3/13/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com>

thank you John. Very useful information. I will talk to EarthX about dual batteries.


Why dual batteries?

When the alternator quits, you have to budget
chemical energy on board to achieve design
goals for altenrator-out endurance.

The e-bus was crafted long before electrically
dependent engines were popular . . . it's
application was pretty narrowly focused on
running the minimum suite of electronics
to get you to intended destination with
no alternator. I.e. ELECTRICAL endurance
could easily outpace FUEL endurance.

Now, with a 14A running load for an engine,
you're probably not hoping for that kind
of electrical endurance. An 18A total
running load for 3+ hours is a pretty
fat battery in lead acid . . . but maybe,
just maybe achievable with a practical
weight/volume in lithium.

For all practical purposes, your alternator
out energy needs for engine and avionics
are the same . . . I think I'd concentrate
on achieving the total energy package
needed for what ever endurance number you
pick. If you can make it equal or greater
than fuel aboard, great. If not practical, then
KNOW what that endurance number is and
orchestrate your Plan-B operations to
fit within that limit.

Applying two batteries to separate
tasks is not very helpful to that
goal. An optimal two-battery configuration
would call for the avionics battery to
be about 1/3 the size of the engine
battery. I think it more practical to
treat the energy needs for flight as
a total package than as two separate
packages. Now, it MIGHT take two
batteries in parallel . . . that's
driven by the energy numbers and your
weight/volume/dollars limits.




Bob . . .


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PostPosted: Fri Mar 15, 2019 8:48 am    Post subject: Three Questions on Z-07 Reply with quote

At 07:35 AM 3/15/2019, you wrote:
Quote:
At 07:45 PM 3/13/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com>

thank you John. Very useful information. I will talk to EarthX about dual batteries.

Why dual batteries?

When the alternator quits, you have to budget
chemical energy on board to achieve design
goals for altenrator-out endurance.

I'll have to dig back in the archives to
retrieve the conversations going on while
Z07 was being discussed. Note that the
drawing is watermarked 'Work in Progresss'.

Given the availability of high volume/energy
ratio of lithium batteries; I'm having trouble
justifying a Z07 architecture.

If anyone can champion the idea, I'd be
please to see their argument posted here
on the List . . . but at the present time,
I'm inclined to pull that drawing down.



Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1900
Location: Riley TWP Michigan

PostPosted: Fri Mar 15, 2019 10:52 am    Post subject: Re: Three Questions on Z-07 Reply with quote

I would leave that drawing available unless there is some unknown failure
mode. There are different strokes for different folks. Someone will have a
perceived need that Z-07 will fill.
I would like to see a very simple architecture without an endurance bus or
diodes. It would be designed with the low power requirements (<20Amp) of
glass panels and LED lighting in mind. Many glass panels have an internal
backup battery good for an hour.
A builder of an IFR RV-10 might want all of the bells and whistles. A builder of a
small and slow two place airplane might prefer simplicity.


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PostPosted: Sat Mar 16, 2019 6:11 am    Post subject: Three Questions on Z-07 Reply with quote

At 01:52 PM 3/15/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com>

I would leave that drawing available unless there is some unknown failure
mode. There are different strokes for different folks. Someone will have a
perceived need that Z-07 will fill.

"Perception" is the key term here . . . where
I have to ask, what are the failure modes being
addressed and what are the numbers that support
the selection of hardware.

A finely tuned Z07 might call for a 24 a.h.
engine battery and a 10 a.h. device for
avionics. But to what end? BOTH batteries
are expected and maintained to meet the same
design endurance. What then is the value for
having two batteries versus one battery
with the same energy content?

I don't recall the discussions now that
prompted the Z07 explorations . . . but
I don't see that it makes sense now.



Bob . . .


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kenryan



Joined: 20 Oct 2009
Posts: 423

PostPosted: Sat Mar 16, 2019 7:22 am    Post subject: Three Questions on Z-07 Reply with quote

The best reason I can think of to have two batteries is to get the engine started if the primary battery doesn't get the job done, and you happen to be on some remote Alaskan gravel bar. Many modern aircraft cannot be hand propped.

On Sat, Mar 16, 2019 at 6:15 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

Quote:
At 01:52 PM 3/15/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com (fransew(at)gmail.com)>

I would leave that drawing available unless there is some unknown failure
mode.  There are different strokes for different folks.  Someone will have a
perceived need that Z-07 will fill.

  "Perception" is the key term here . . . where
  I have to ask, what are the failure modes being
  addressed and what are the numbers that support
  the selection of hardware.

  A finely tuned Z07 might call for a 24 a.h.
  engine battery and a 10 a.h. device for
  avionics. But to what end? BOTH batteries
  are expected and maintained to meet the same
  design endurance. What then is the value for
  having two batteries versus one battery
  with the same energy content?

  I don't recall the discussions now that
  prompted the Z07 explorations . . . but
  I don't see that it makes sense now.



  Bob . . .


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user9253



Joined: 28 Mar 2008
Posts: 1900
Location: Riley TWP Michigan

PostPosted: Sat Mar 16, 2019 10:20 am    Post subject: Re: Three Questions on Z-07 Reply with quote

Sudden battery failure is rare, but it has happened . . . to me. My PC680
cranked the engine just fine. Then later, when I reduced throttle to land, the
EFIS rebooted. The EFIS did not have an internal backup battery at the time,
but now does. I sent the battery to Bob N. and he found a broken
internal weld. I still only have one battery not counting the backup batteries inside of avionics.
Each builder will wire their airplane the way that they want to. All we can
do is educate them so that they can make informed decisions. A friend
installed an avionics switch in his panel. I told him that the need for that
switch is based on an old wives tale that has been handed down from
instructor to student. And I told him that switch makes his airplane less safe.
But I was only one person. Several others told my friend to install that
switch. So he did.
Some builders are willing to sacrifice money and performance for their
peace of mind. All we can do is look over their shoulder and point out
anything that is dangerous. If a builder wants to install two large
batteries, he will do it whether there is a Z figure for it or not.
Without guidance, his architecture could have a design flaw


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PostPosted: Sun Mar 17, 2019 8:18 am    Post subject: Three Questions on Z-07 Reply with quote

At 10:19 AM 3/16/2019, you wrote:
Quote:
The best reason I can think of to have two batteries is to get the engine started if the primary battery doesn't get the job done, and you happen to be on some remote Alaskan gravel bar. Many modern aircraft cannot be hand propped.

One battery, sized and MAINTAINED for the
task will never fail to get the engine
started.

Cranking the engine requires but 3-6
percent of a battery's contained
energy . . . a trivial sum. If the
battery fails to get an engine started,
it's axiomatic that it's suitability
for continued flight has long since
past.



Bob . . .


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kenryan



Joined: 20 Oct 2009
Posts: 423

PostPosted: Sun Mar 17, 2019 9:21 am    Post subject: Three Questions on Z-07 Reply with quote

"One battery, sized and MAINTAINED for the
 task will never fail to get the engine started."

I get your point Bob, but never say never. We already have one well respected report of battery failure, not attributable to abuse, just from the very small sample that consists of the current active members of this list. (You yourself did the autopsy.)

And remember, we are not all flying airport to airport, or landing in some farmer's field in Kansas, next to the Interstate (or even county road). Here in Alaska, we might be landing at some unimproved strip on the tundra, 150 miles from the nearest road. This would be commonplace here. Also consider cold weather operations where the battery might not be performing at 100% and the engine might be stiff (and you might be sitting at some remote landing spot with the 4 hours of available daylight fading quickly).
The consequences of a non-start on the engine vary so much depending upon the circumstances, I submit that it is not at all unreasonable to either incorporate a second starting battery, or at least carry one.
Ken

On Sun, Mar 17, 2019 at 8:22 AM Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:

Quote:
At 10:19 AM 3/16/2019, you wrote:
Quote:
The best reason I can think of to have two batteries is to get the engine started if the primary battery doesn't get the job done, and you happen to be on some remote Alaskan gravel bar. Many modern aircraft cannot be hand propped.

 One battery, sized and MAINTAINED for the
 task will never fail to get the engine
 started.

 Cranking the engine requires but 3-6
 percent of a battery's contained
 energy . . . a trivial sum. If the
 battery fails to get an engine started,
 it's axiomatic that it's suitability
 for continued flight has long since
 past.



  Bob . . .


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PostPosted: Sun Mar 17, 2019 10:53 am    Post subject: Three Questions on Z-07 Reply with quote

At 12:06 PM 3/17/2019, you wrote:
Quote:
"One battery, sized and MAINTAINED for the
task will never fail to get the engine
started."

I get your point Bob, but never say never. We already have one well respected report of battery failure, not attributable to abuse, just from the very small sample that consists of the current active members of this list. (You yourself did the autopsy.)

And remember, we are not all flying airport to airport, or landing in some farmer's field in Kansas, next to the Interstate (or even county road). Here in Alaska, we might be landing at some unimproved strip on the tundra, 150 miles from the nearest road. This would be commonplace here. Also consider cold weather operations where the battery might not be performing at 100% and the engine might be stiff (and you might be sitting at some remote landing spot with the 4 hours of available daylight fading quickly).

The consequences of a non-start on the engine vary so much depending upon the circumstances, I submit that it is not at all unreasonable to either incorporate a second starting battery, or at least carry one.

No argument . . . that's what FMEA,
load analysis, preventative maintenance,
and matching the hardware to the mission
is all about. How many of the GA fleet
lands on floats anywhere much less
on remote lakes in the NW Territories?

(BTW, about 20 years ago, I did a drawing
for an Alaskan bush pilot adding an
auxiliary battery to the interior of
one of his floats.

Lots of unused volume there. Mounting
the battery there didn't penalize
volume in the aircraft and was easier
to manage structurally)

There are NO broad brush recommendations
here . . . only an encouragement to
match machine and pilot to the task
while maximizing utility and minimizing
risk . . . a start-stick might well
fill the bill. But Z07 was never completed.
If the List wishes to 'fine tune' this
architecture, I'd be pleased to participate
in cogent argument.



Bob . . .


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markfw



Joined: 28 Feb 2019
Posts: 27
Location: Seattle, WA

PostPosted: Sun Mar 17, 2019 12:43 pm    Post subject: Re: Three Questions on Z-07 Reply with quote

Bob,

I have assumed that I would use two batteries for 4 reasons:

1. I believed that there was a requirement to have a working battery to (magically to me) "cushion" delicate avionics from the alternator current;
2. I assumed that I could parallel the LiFePO4 batteries to aid in starting
3. I was trying to guard against a battery failure "from bringing down the whole system".
4. It is easier for me to mount two smaller batteries in parallel than one large one given my alternator-out mission requirements.

It seems that reason #1 is bogus, since your discussion of "one large battery" assumes that the alternator alone can run everything required without a problem. I don't know where I got this idea.

Reason #2 turns out to (maybe) be bogus as well. Two manufacturers who supply a BMS with their LiFePo4 batteries recommend AGAINST running their batteries in parallel. Apparently, low resistance in a single cell of these multi-cell LiFePO4 batteries can greatly reduce capacity and longevity. The manufacturers take great care to match the resistance of the battery cells when they build them, and their BMS's spend a lot of time "optimizing" the batteries during charge and discharge. This is not possible between paralleled batteries and a Resistance mismatch between the batteries of (for example) 20% can reduce performance by 40%.

On the other hand another manufacturer who does not supply a BMS with their batteries says nothing about this. A friend of mine has used their product in parallel for 3 years without problem.

So, your Z-07 diagram without parallel batteries may still be useful for people who believe this is a problem for them.

Reason #3 was actually a quote from your 1998 paper "What's all this Battery Isolator Stuff Anyhow?". I have also heard it mentioned in various discussions of dual battery installations. As you point out in your 2008 paper "Myths of Multiple Battery Installation" a shorted cell is exceedingly rare. However, in an electrically dependent airplane, "rare" is in the eye of the beholder. Is there any data on this? Given the cell resistance issue LiFePO4 batteries might that chemistry be more susceptible to this problem?

Finally, reason #4 is a problem that you mention and is certainly not unique to my situation. My current theory is to use the TCW backup battery solution. It is automatic, does not parallel the batteries and is a lightweight LiFePO4 solution. The disadvantage is that (currently) it is limited to a 6 amp/hr capacity, which is 30 minutes for me throttled back if I lost BOTH my alternator and primary battery.

Yes, this is non-FEMA thinking to worry about two failures at the same time. I think that it depends on what the definition of "bringing down the whole system" is. If a shorted battery cell can somehow stop the alternator from functioning, isn't that actually one failure?

Mark


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PostPosted: Mon Mar 18, 2019 7:20 am    Post subject: Three Questions on Z-07 Reply with quote

At 03:43 PM 3/17/2019, you wrote:
Quote:
--> AeroElectric-List message posted by: "markfw" <markwheelermd(at)icloud.com>

Bob,

I have assumed that I would use two batteries for 4 reasons:

1. I believed that there was a requirement to have a working battery to (magically to me) "cushion" delicate avionics from the alternator current;

not true

Quote:
2. I assumed that I could parallel the LiFePO4 batteries to aid in starting

sure . . . would one larger battery do it too?

Quote:
3. I was trying to guard against a battery failure "from bringing down the whole system".

battery failures don't bring down the whole system.
The alternator will run self excited and you
probably wouldn't know that the battery was
gone until you shut the alternator off.

Quote:
4. It is easier for me to mount two smaller batteries in parallel than one large one given my alternator-out mission requirements.

available space can drive battery
configuration . . .


Quote:
It seems that reason #1 is bogus, since your discussion of "one large battery" assumes that the alternator alone can run everything required without a problem. I don't know where I got this idea.

Reason #2 turns out to (maybe) be bogus as well. Two manufacturers who supply a BMS with their LiFePo4 batteries recommend AGAINST running their batteries in parallel. Apparently, low resistance in a single cell of these multi-cell LiFePO4 batteries can greatly reduce capacity and longevity. The manufacturers take great care to match the resistance of the battery cells when they build them, and their BMS's spend a lot of time "optimizing" the batteries during charge and discharge. This is not possible between paralleled batteries and a Resistance mismatch between the batteries of (for example) 20% can reduce performance by 40%.

I don't see how this is possible. How does one
battery with a BMS know that there's another
battery on line with it? The bus voltage is
a function of regulator set point. Bus voltage
is the sole determinant for optimal charging
of the battery. The fact that a second battery
shares the bus is totally transparent to the
first battery.


Quote:
On the other hand another manufacturer who does not supply a BMS with their batteries says nothing about this. A friend of mine has used their product in parallel for 3 years without problem.

Exactly. This is what battery charge
balancing is all about. If any single
cell (or cell group) is lagging behind
the rest in achieving full charge (due
perhaps to slightly lower impedance)
then the balancing system places an
artificial load on the remaining cells
in the string until the lagging cell
catches up.


Quote:
So, your Z-07 diagram without parallel batteries may still be useful for people who believe this is a problem for them.

Believing is subordinate to knowing . . .
knowing is subordinate to understanding.

Quote:
Reason #3 was actually a quote from your 1998 paper "What's all this Battery Isolator Stuff Anyhow?". I have also heard it mentioned in various discussions of dual battery installations. As you point out in your 2008 paper "Myths of Multiple Battery Installation" a shorted cell is exceedingly rare. However, in an electrically dependent airplane, "rare" is in the eye of the beholder. Is there any data on this? Given the cell resistance issue LiFePO4 batteries might that chemistry be more susceptible to this problem?

If it worries you, you'd better find out.
Just suppose you have two batteries
with their own contactors? How would you become
aware that you had a shorted cell? How would
you know which battery to take off line?
If a cell were shorted in one battery, how
do you know that taking the battery off
line will markedly reduce risk? Each
failure has it's own fingerprint (or
failureprint) in how it manifests,
progresses, propagates and terminates.
Hence, each failure has an optimal
response that drives toward a probable outcome.


Quote:
Finally, reason #4 is a problem that you mention and is certainly not unique to my situation. My current theory is to use the TCW backup battery solution. It is automatic, does not parallel the batteries and is a lightweight LiFePO4 solution. The disadvantage is that (currently) it is limited to a 6 amp/hr capacity, which is 30 minutes for me throttled back if I lost BOTH my alternator and primary battery.

Nobody looses BOTH unless they've done
something really dumb. What kind
of engine are we talking about?


Quote:
Yes, this is non-FEMA thinking to worry about two failures at the same time. I think that it depends on what the definition of "bringing down the whole system" is. If a shorted battery cell can somehow stop the alternator from functioning, isn't that actually one failure?

A shorted cell won't bring down the
alternator. It will probably proceed
to spectacular if not catastrophic
failure in the battery itself . . . recall
that a lithium cell contains a lot of
energy with respect to weight/volume.
That energy has to go somewhere . . . usually
toward warming things up and making really
bad smells. SVLA cells are not particularly
failure friendly either.

So the question before us is exactly what
are the probabilities for an LiFePO4 cell-
short? If it does short, what are the
electrical and physical consequences?

I used to have some friendly contacts at
the Navy's battery testing facilities
in Crane, Indiana. If any battery was
purchased by the Navy, they had put it
through rigorous tests including abuses
designed to produce the greatest risks.

TrueBlue has done extensive testing on
LiFePo4, cylindrical cells used in their
TSO/PMA offerings to TC aircraft. I've
witnessed some tests where a constant
42 volts was placed across the array
of cells in a 24v battery. The poor things
went into apoplectic self-destruction
with considerable out-gassing. Gasses
were vented overboard though the fitting
on top. Outside of the case never reached
temperatures hazardous to the aircraft's
environs.

[img]cid:.0[/img]

I can also tell you that the volume of
electronics in these products is roughly
equal to the volume of batteries . . .
the BMS is specifically tasked with
preventing such a failure in the
first place.

It seems to be a choice of products. Just
how much BMS you want to buy ranging
from EarthX down to no BMS like Aerovoltz
. . . or you could pop for True Blue.

Aircraft Spruce covers the range . . .

https://tinyurl.com/y4o5xwuz

ACS has a world-wide market and
deep pockets at risk for very deep picking
should one of their offerings prove
dangerously unsuited to task.

Z07 as last published has lots of
bus structures which, in an electrically
dependent airplane could probably go
away. Wiring this up like a C150 but
with engine dependency serviced directly
from the battery bus is probably the
way to go.

You can go max-cold for smoke in the
cockpit while keeping that whirrly thing
up front turning. You can simply load-shed
in case of alternator failure. If you've
got enough chemical energy on board to
meet satisfactory endurance goals, splitting
that capacity between two, separately
controlled batteries doesn't seem to make
sense.


Bob . . .


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