Today's Message Index:
----------------------
1. 10:20 AM - Speaking of LiFePo4 (Robert L. Nuckolls, III)
2. 01:09 PM - Re: Speaking of LiFePo4 (Ken Ryan)
3. 03:02 PM - Re: Re: Physical construction of Z101 engine bus & battery bus (Matthew S. Whiting)
4. 03:02 PM - Re: Speaking of LiFePo4 (David Carter)
5. 03:14 PM - Re: Speaking of LiFePo4 (C&K)
6. 03:43 PM - Re: Speaking of LiFePo4 (Sebastien)
7. 03:48 PM - Z101 with Rotax 915iS (Matthew S. Whiting)
8. 03:49 PM - Re: Re: Physical construction of Z101 engine bus & battery bus (Charlie England)
9. 03:51 PM - Re: Speaking of LiFePo4 (Lyle Peterson)
10. 04:54 PM - Re: Speaking of LiFePo4 (Matthew S. Whiting)
11. 05:24 PM - Re: Z101 with Rotax 915iS (user9253)
12. 05:25 PM - Re: Z101 with Rotax 915iS (Ken Ryan)
13. 05:27 PM - Re: Re: Physical construction of Z101 engine bus & battery bus (Matthew S. Whiting)
14. 05:30 PM - Re: Speaking of LiFePo4 (Ken Ryan)
15. 07:34 PM - Re: Re: Z101 with Rotax 915iS (Ken Ryan)
16. 07:34 PM - Re: Re: Z101 with Rotax 915iS (Matthew S. Whiting)
Message 1
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| Subject: | Speaking of LiFePo4 |
At 04:33 PM 6/11/2020, you wrote:
>
>Dear all,
>
>Better not confuse LiPo with LiFePO4 (also called LFP). Important differences.
>A search with both terms will lead to some clarity I expect.
An very important point. Not all 'lithium' cells
are the same. While the energy density is
higher for chemistries other than lithium
iron phosphate (LiFePo4), the relative
robustness and safety of the LiFePo4
devices has prompted a chemistry of choice
decision for most suppliers to our craft . . .
indeed most consumer motive power applications.
For our purposes, when ever I refer to
a lithium product, know that I'm referring
to the LiFePo4 technology.
Speaking of LiFePo4:
I observe that virtually all the COTS lithium
chargers in my stable, every one 'tops off'
at 4.2 volts. These chargers were used to
explore qualities of a bevy of 18650
cells laying around the shop. I've
attached a plot for a constellation
of cells. A plot of the as-found condition
of a cell was followed by a plot of a
recharged condition.
Most of the 'weak' cells showed marked
recovery . . . others did not. One interesting
feature of this exercise is to note the
starting voltage for the discharge plot
of each recharged cell.
Virtually all produced first delivery of
energy at 4.0 volts or more. Hmmm . . .
It seems this was related to charging
top-off voltage. Okay, if one wishes
to maximize exploitation of your ship'
lithium battery, do you want to raise
your alternator voltage to 4 x 4.2
16.8 volts?
Hmmm . . . most of our electro whizzies
probably wouldn't mind . . . but if you're
carrying incandescent lights of any size,
service life would be reduced by 50% or more . . .
but they would certainly be bright!
I've posted an article found on powerstream.com
See: https://tinyurl.com/yazw9jnh
By the way, check out the rest of this website.
It's a treasure trove of data on DC power
systems. I had the name of the author at
one time but let it get lost. If anyone
perusing this resource runs across the author's
name, I'd appreciate a heads-up.
The article illustrates some interesting numbers
on LiFePo4 performance. First, there is
little value in charging the LiFePo4 cell
at it rated maximum. The writer demonstrates
that charging at considerably lower levels
does not significantly affect stored energy
until charge-per-cell voltage drops below
3.40. Okay, 3.40 x 4 is 13.6 volts. I
think we can live with that!
In fact, we're told that the charge-discharge
service life of lithium cells is improved
by operating the cells between 30 and 90%
of the chemical capacity of the cell. Okay
operating the contemporary 4-cell array
products at the legacy 14.2 to 14.4 volts
(3.6 volts per cell) wont give up significant
performance while extending service life.
I'm going to repeat the experiment in the
article cited. I will add features
that explore system integration questions
going to what may prove to be the 'next
generation' of OBAM aviation electrical system
architectures.
Bob . . .
Message 2
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| Subject: | Re: Speaking of LiFePo4 |
Okay, 20 minutes with google reveals plenty of examples of COTS chargers,
but no definition of COTS. Could someone please educate me on this
terminology? Thanks.
On Fri, Jun 12, 2020 at 9:27 AM Robert L. Nuckolls, III <
nuckolls.bob@aeroelectric.com> wrote:
> At 04:33 PM 6/11/2020, you wrote:
>
> jan_de_jong@casema.nl>
>
> Dear all,
>
> Better not confuse LiPo with LiFePO4 (also called LFP). Important
> differences.
> A search with both terms will lead to some clarity I expect.
>
>
> An very important point. Not all 'lithium' cells
> are the same. While the energy density is
> higher for chemistries other than lithium
> iron phosphate (LiFePo4), the relative
> robustness and safety of the LiFePo4
> devices has prompted a chemistry of choice
> decision for most suppliers to our craft . . .
> indeed most consumer motive power applications.
>
> For our purposes, when ever I refer to
> a lithium product, know that I'm referring
> to the LiFePo4 technology.
>
> Speaking of LiFePo4:
>
> I observe that virtually all the COTS lithium
> chargers in my stable, every one 'tops off'
> at 4.2 volts. These chargers were used to
> explore qualities of a bevy of 18650
> cells laying around the shop. I've
> attached a plot for a constellation
> of cells. A plot of the as-found condition
> of a cell was followed by a plot of a
> recharged condition.
>
> Most of the 'weak' cells showed marked
> recovery . . . others did not. One interesting
> feature of this exercise is to note the
> starting voltage for the discharge plot
> of each recharged cell.
>
> Virtually all produced first delivery of
> energy at 4.0 volts or more. Hmmm . . .
> It seems this was related to charging
> top-off voltage. Okay, if one wishes
> to maximize exploitation of your ship'
> lithium battery, do you want to raise
> your alternator voltage to 4 x 4.2
> 16.8 volts?
>
> Hmmm . . . most of our electro whizzies
> probably wouldn't mind . . . but if you're
> carrying incandescent lights of any size,
> service life would be reduced by 50% or more . . .
> but they would certainly be bright!
>
> I've posted an article found on powerstream.com
>
> See: https://tinyurl.com/yazw9jnh
>
> By the way, check out the rest of this website.
> It's a treasure trove of data on DC power
> systems. I had the name of the author at
> one time but let it get lost. If anyone
> perusing this resource runs across the author's
> name, I'd appreciate a heads-up.
>
> The article illustrates some interesting numbers
> on LiFePo4 performance. First, there is
> little value in charging the LiFePo4 cell
> at it rated maximum. The writer demonstrates
> that charging at considerably lower levels
> does not significantly affect stored energy
> until charge-per-cell voltage drops below
> 3.40. Okay, 3.40 x 4 is 13.6 volts. I
> think we can live with that!
>
> In fact, we're told that the charge-discharge
> service life of lithium cells is improved
> by operating the cells between 30 and 90%
> of the chemical capacity of the cell. Okay
> operating the contemporary 4-cell array
> products at the legacy 14.2 to 14.4 volts
> (3.6 volts per cell) wont give up significant
> performance while extending service life.
>
> I'm going to repeat the experiment in the
> article cited. I will add features
> that explore system integration questions
> going to what may prove to be the 'next
> generation' of OBAM aviation electrical system
> architectures.
>
> Bob . . .
>
Message 3
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| Subject: | Re: Physical construction of Z101 engine bus & |
battery bus
It seems to me the real question is which is more likely to fail:
1. A single battery with an age of 0 - 2 years or
2. Both batteries simultaneously where one is 0 - 2 years old and the other is
2 - 4 years old?
I am not aware of a good source of battery failure rates, but my auto experience
over the course of 45 years suggests that alternative 1 has a much higher probability
than alternative 2. I have almost always had at least four cars, trucks
and motorcycles at any given time with battery ages between new and 8 years
old. Even if I discount failures of batteries more than 4 years old (I tend
to run my car batteries to failure), I have had at least two failures I can
remember of with batteries less than two years old. My Current Chevy Equinox
OEM battery failed 5 months after I bought the vehicle new in 2012. No charging
system issues were found and the warranty replacement battery lasted 6 years.
I have NEVER had two of my vehicles have battery failures at the same time
or even closely spaced in time. That suggests to me that the probability of a
single new battery failing is higher than the probability of simultaneous failure
of two batteries: one new and one older.
I realize this isnt exactly the same scenario since two batteries in the same vehicle
could have a common failure mode such as a runaway alternator that fries
them both, but it is the best I can do.
Matt
> On Jun 12, 2020, at 4:50 PM, Alec Myers <alec@alecmyers.com> wrote:
>
>
> Joe,
>
> Just to play devils advocate, if youre prepared to replace a new battery every
other year, then if you only have one battery, the worst case is that its 2
years old. And youre not schlepping a 4 year old battery around with you.
> Your mean battery age with two batteries would be three years; with a single
battery the mean age is only one year, an improvement by a factor of 3.
Message 4
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| Subject: | Re: Speaking of LiFePo4 |
Commercial-of-the-shelf. Often used in the government contracting world &
the opposite of bespoke.
On Fri, Jun 12, 2020 at 4:12 PM Ken Ryan <keninalaska@gmail.com> wrote:
> Okay, 20 minutes with google reveals plenty of examples of COTS chargers,
> but no definition of COTS. Could someone please educate me on this
> terminology? Thanks.
>
>
> On Fri, Jun 12, 2020 at 9:27 AM Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> At 04:33 PM 6/11/2020, you wrote:
>>
>> jan_de_jong@casema.nl>
>>
>> Dear all,
>>
>> Better not confuse LiPo with LiFePO4 (also called LFP). Important
>> differences.
>> A search with both terms will lead to some clarity I expect.
>>
>>
>> An very important point. Not all 'lithium' cells
>> are the same. While the energy density is
>> higher for chemistries other than lithium
>> iron phosphate (LiFePo4), the relative
>> robustness and safety of the LiFePo4
>> devices has prompted a chemistry of choice
>> decision for most suppliers to our craft . . .
>> indeed most consumer motive power applications.
>>
>> For our purposes, when ever I refer to
>> a lithium product, know that I'm referring
>> to the LiFePo4 technology.
>>
>> Speaking of LiFePo4:
>>
>> I observe that virtually all the COTS lithium
>> chargers in my stable, every one 'tops off'
>> at 4.2 volts. These chargers were used to
>> explore qualities of a bevy of 18650
>> cells laying around the shop. I've
>> attached a plot for a constellation
>> of cells. A plot of the as-found condition
>> of a cell was followed by a plot of a
>> recharged condition.
>>
>> Most of the 'weak' cells showed marked
>> recovery . . . others did not. One interesting
>> feature of this exercise is to note the
>> starting voltage for the discharge plot
>> of each recharged cell.
>>
>> Virtually all produced first delivery of
>> energy at 4.0 volts or more. Hmmm . . .
>> It seems this was related to charging
>> top-off voltage. Okay, if one wishes
>> to maximize exploitation of your ship'
>> lithium battery, do you want to raise
>> your alternator voltage to 4 x 4.2
>> 16.8 volts?
>>
>> Hmmm . . . most of our electro whizzies
>> probably wouldn't mind . . . but if you're
>> carrying incandescent lights of any size,
>> service life would be reduced by 50% or more . . .
>> but they would certainly be bright!
>>
>> I've posted an article found on powerstream.com
>>
>> See: https://tinyurl.com/yazw9jnh
>>
>> By the way, check out the rest of this website.
>> It's a treasure trove of data on DC power
>> systems. I had the name of the author at
>> one time but let it get lost. If anyone
>> perusing this resource runs across the author's
>> name, I'd appreciate a heads-up.
>>
>> The article illustrates some interesting numbers
>> on LiFePo4 performance. First, there is
>> little value in charging the LiFePo4 cell
>> at it rated maximum. The writer demonstrates
>> that charging at considerably lower levels
>> does not significantly affect stored energy
>> until charge-per-cell voltage drops below
>> 3.40. Okay, 3.40 x 4 is 13.6 volts. I
>> think we can live with that!
>>
>> In fact, we're told that the charge-discharge
>> service life of lithium cells is improved
>> by operating the cells between 30 and 90%
>> of the chemical capacity of the cell. Okay
>> operating the contemporary 4-cell array
>> products at the legacy 14.2 to 14.4 volts
>> (3.6 volts per cell) wont give up significant
>> performance while extending service life.
>>
>> I'm going to repeat the experiment in the
>> article cited. I will add features
>> that explore system integration questions
>> going to what may prove to be the 'next
>> generation' of OBAM aviation electrical system
>> architectures.
>>
>> Bob . . .
>>
> --
---
David Carter
david@carter.net
Message 5
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| Subject: | Re: Speaking of LiFePo4 |
Commercial Off The Shelf rather than custom made
On 12/06/2020 3:45 PM, Ken Ryan wrote:
> Okay, 20 minutes with google reveals plenty of examples of COTS
> chargers, but no definition of COTS. Could someone please educate me
> on this terminology? Thanks.
>
>
Message 6
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| Subject: | Re: Speaking of LiFePo4 |
Commercial Of The Shelf.
In other words purchaseable.
On Fri, Jun 12, 2020, 13:14 Ken Ryan <keninalaska@gmail.com> wrote:
> Okay, 20 minutes with google reveals plenty of examples of COTS chargers,
> but no definition of COTS. Could someone please educate me on this
> terminology? Thanks.
>
>
> On Fri, Jun 12, 2020 at 9:27 AM Robert L. Nuckolls, III <
> nuckolls.bob@aeroelectric.com> wrote:
>
>> At 04:33 PM 6/11/2020, you wrote:
>>
>> jan_de_jong@casema.nl>
>>
>> Dear all,
>>
>> Better not confuse LiPo with LiFePO4 (also called LFP). Important
>> differences.
>> A search with both terms will lead to some clarity I expect.
>>
>>
>> An very important point. Not all 'lithium' cells
>> are the same. While the energy density is
>> higher for chemistries other than lithium
>> iron phosphate (LiFePo4), the relative
>> robustness and safety of the LiFePo4
>> devices has prompted a chemistry of choice
>> decision for most suppliers to our craft . . .
>> indeed most consumer motive power applications.
>>
>> For our purposes, when ever I refer to
>> a lithium product, know that I'm referring
>> to the LiFePo4 technology.
>>
>> Speaking of LiFePo4:
>>
>> I observe that virtually all the COTS lithium
>> chargers in my stable, every one 'tops off'
>> at 4.2 volts. These chargers were used to
>> explore qualities of a bevy of 18650
>> cells laying around the shop. I've
>> attached a plot for a constellation
>> of cells. A plot of the as-found condition
>> of a cell was followed by a plot of a
>> recharged condition.
>>
>> Most of the 'weak' cells showed marked
>> recovery . . . others did not. One interesting
>> feature of this exercise is to note the
>> starting voltage for the discharge plot
>> of each recharged cell.
>>
>> Virtually all produced first delivery of
>> energy at 4.0 volts or more. Hmmm . . .
>> It seems this was related to charging
>> top-off voltage. Okay, if one wishes
>> to maximize exploitation of your ship'
>> lithium battery, do you want to raise
>> your alternator voltage to 4 x 4.2
>> 16.8 volts?
>>
>> Hmmm . . . most of our electro whizzies
>> probably wouldn't mind . . . but if you're
>> carrying incandescent lights of any size,
>> service life would be reduced by 50% or more . . .
>> but they would certainly be bright!
>>
>> I've posted an article found on powerstream.com
>>
>> See: https://tinyurl.com/yazw9jnh
>>
>> By the way, check out the rest of this website.
>> It's a treasure trove of data on DC power
>> systems. I had the name of the author at
>> one time but let it get lost. If anyone
>> perusing this resource runs across the author's
>> name, I'd appreciate a heads-up.
>>
>> The article illustrates some interesting numbers
>> on LiFePo4 performance. First, there is
>> little value in charging the LiFePo4 cell
>> at it rated maximum. The writer demonstrates
>> that charging at considerably lower levels
>> does not significantly affect stored energy
>> until charge-per-cell voltage drops below
>> 3.40. Okay, 3.40 x 4 is 13.6 volts. I
>> think we can live with that!
>>
>> In fact, we're told that the charge-discharge
>> service life of lithium cells is improved
>> by operating the cells between 30 and 90%
>> of the chemical capacity of the cell. Okay
>> operating the contemporary 4-cell array
>> products at the legacy 14.2 to 14.4 volts
>> (3.6 volts per cell) wont give up significant
>> performance while extending service life.
>>
>> I'm going to repeat the experiment in the
>> article cited. I will add features
>> that explore system integration questions
>> going to what may prove to be the 'next
>> generation' of OBAM aviation electrical system
>> architectures.
>>
>> Bob . . .
>>
>
Message 7
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| Subject: | Z101 with Rotax 915iS |
This is my first post to the mailing list so hopefully I get it reasonably right.
I am not sure if this best fits this list or the Rotax engine list, but will
start here.
For context, I am a retired CS/EE and about to start my first home built project.
My RANS S-21 is scheduled to ship in July. I plan to use a Rotax 915iS engine
and am looking now at electrical system and avionics.
I have read the Connection book and perused some of the newer Z architectures at
the web site. I am leaning towards a Z101 configuration as the baseline, but
the problem is that the Rotax comes with only one generator (I know it has two,
but I believe the small one is only available to run the engine and not available
for ships power). Rotax sells an external alternator kit, but a quick
tally of the parts shows the cost to be north of $2,000 and I see nothing yet
in the aftermarket.
So, I am curious as to whether anyone here has installed a 915iS and, if so, what
electrical system architecture did you choose. And, is anyone aware of alternative
way to add a second alternator/generator to a 915iS or is the Rotax option
the only game in town?
My second choice is a second battery to back up the avionics and engine should
the unthinkable happen and both alternators fail and the primary battery not have
enough reserve to get to a safe landing site. Id much rather have a second
alternator than a second battery, but $2,000 seems a little steep for an alternator
that likely will never get used and a second battery at least has the
advantage of extra starting reserve on our cold winter days in northern PA.
Regards,
Matt Whiting
Sent from my iPad
Message 8
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| Subject: | Re: Physical construction of Z101 engine bus & |
battery bus
I think that when doing failure analysis, you don't really pay that much
attention to odds; you play 'what if'. (Actually, 'when it fails'; the
assumption when doing failure analysis is that anything we can back up
*will* fail). You do have to take uncontrollable stuff out of the equation;
we can't carry an extra set of wings, for instance, and most of us accept
the risk of a single engine, in order to be able to fly at all.
Once that's out of the way, then 'what if' starts. What if the alternator
fails? It's taken off line and battery backs it up. What if the battery
fails? It's taken off line and the alternator backs it up (contrary to
popular internet lore). If the engine isn't electrically dependent and
we're VFR with nav on our phone, we don't even care about backup at all.
The what if of both failing in a single flight is considered to be so
unlikely that most are willing to treat a double failure like a wing or
other structural failure; we're just not going to go there.
My personal choice with a high-amps-need engine control system is to not
accept the limited and continuously decreasing duration (capacity) of a
standard battery, nor to accept the weight penalty of a much bigger battery
or multiple batteries, in order to keep the engine running to the end of
the flight. For me, that only leaves the choice of dual alternators.
FWIW,
Charlie
On Fri, Jun 12, 2020 at 5:09 PM Matthew S. Whiting <m.whiting@frontier.com>
wrote:
> m.whiting@frontier.com>
>
>
> It seems to me the real question is which is more likely to fail:
>
> 1. A single battery with an age of 0 - 2 years or
> 2. Both batteries simultaneously where one is 0 - 2 years old and the
> other is 2 - 4 years old?
>
> I am not aware of a good source of battery failure rates, but my auto
> experience over the course of 45 years suggests that alternative 1 has a
> much higher probability than alternative 2. I have almost always had at
> least four cars, trucks and motorcycles at any given time with battery ag
es
> between new and 8 years old. Even if I discount failures of batteries mo
re
> than 4 years old (I tend to run my car batteries to failure), I have had
at
> least two failures I can remember of with batteries less than two years
> old. My Current Chevy Equinox OEM battery failed 5 months after I bought
> the vehicle new in 2012. No charging system issues were found and the
> warranty replacement battery lasted 6 years. I have NEVER had two of my
> vehicles have battery failures at the same time or even closely spaced in
> time. That suggests to me that the probability of a single new battery
> failing is higher than the probability of simultaneous failure of two
> batteries: one new and one older.
>
> I realize this isn=99t exactly the same scenario since two batterie
s in the
> same vehicle could have a common failure mode such as a runaway alternato
r
> that fries them both, but it is the best I can do.
>
> Matt
>
>
> > On Jun 12, 2020, at 4:50 PM, Alec Myers <alec@alecmyers.com> wrote:
> >
myers.com
> >
> >
> > Joe,
> >
> > Just to play devil=99s advocate, if you=99re prepared to re
place a new
> battery every other year, then if you only have one battery, the worst ca
se
> is that it=99s 2 years old. And you=99re not schlepping a 4 y
ear old battery
> around with you.
> > Your mean battery age with two batteries would be three years; with a
> single battery the mean age is only one year, an improvement by a factor
of
> 3.
>
>
===========
===========
===========
===========
===========
>
>
Message 9
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| Subject: | Re: Speaking of LiFePo4 |
COTS is what you slept on in the military.
On 6/12/2020 2:45 PM, Ken Ryan wrote:
> Okay, 20 minutes with google reveals plenty of examples of COTS
> chargers, but no definition of COTS. Could someone please educate me
> on this terminology? Thanks.
>
>
> On Fri, Jun 12, 2020 at 9:27 AM Robert L. Nuckolls, III
> <nuckolls.bob@aeroelectric.com <mailto:nuckolls.bob@aeroelectric.com>>
> wrote:
>
> At 04:33 PM 6/11/2020, you wrote:
>> <jan_de_jong@casema.nl <mailto:jan_de_jong@casema.nl>>
>>
>> Dear all,
>>
>> Better not confuse LiPo with LiFePO4 (also called LFP). Important
>> differences.
>> A search with both terms will lead to some clarity I expect.
>
> An very important point. Not all 'lithium' cells
> are the same. While the energy density is
> higher for chemistries other than lithium
> iron phosphate (LiFePo4), the relative
> robustness and safety of the LiFePo4
> devices has prompted a chemistry of choice
> decision for most suppliers to our craft . . .
> indeed most consumer motive power applications.
>
> For our purposes, when ever I refer to
> a lithium product, know that I'm referring
> to the LiFePo4 technology.
>
> Speaking of LiFePo4:
>
> I observe that virtually all the COTS lithium
> chargers in my stable, every one 'tops off'
> at 4.2 volts. These chargers were used to
> explore qualities of a bevy of 18650
> cells laying around the shop. I've
> attached a plot for a constellation
> of cells. A plot of the as-found condition
> of a cell was followed by a plot of a
> recharged condition.
>
> Most of the 'weak' cells showed marked
> recovery . . . others did not. One interesting
> feature of this exercise is to note the
> starting voltage for the discharge plot
> of each recharged cell.
>
> Virtually all produced first delivery of
> energy at 4.0 volts or more. Hmmm . . .
> It seems this was related to charging
> top-off voltage. Okay, if one wishes
> to maximize exploitation of your ship'
> lithium battery, do you want to raise
> your alternator voltage to 4 x 4.2
> 16.8 volts?
>
> Hmmm . . . most of our electro whizzies
> probably wouldn't mind . . . but if you're
> carrying incandescent lights of any size,
> service life would be reduced by 50% or more . . .
> but they would certainly be bright!
>
> I've posted an article found on powerstream.com
> <http://powerstream.com>
>
> See: https://tinyurl.com/yazw9jnh
>
> <https://tinyurl.com/yazw9jnh> By the way, check out the rest of
> this website.
> It's a treasure trove of data on DC power
> systems. I had the name of the author at
> one time but let it get lost. If anyone
> perusing this resource runs across the author's
> name, I'd appreciate a heads-up.
>
> The article illustrates some interesting numbers
> on LiFePo4 performance. First, there is
> little value in charging the LiFePo4 cell
> at it rated maximum. The writer demonstrates
> that charging at considerably lower levels
> does not significantly affect stored energy
> until charge-per-cell voltage drops below
> 3.40. Okay, 3.40 x 4 is 13.6 volts. I
> think we can live with that!
>
> In fact, we're told that the charge-discharge
> service life of lithium cells is improved
> by operating the cells between 30 and 90%
> of the chemical capacity of the cell. Okay
> operating the contemporary 4-cell array
> products at the legacy 14.2 to 14.4 volts
> (3.6 volts per cell) wont give up significant
> performance while extending service life.
>
> I'm going to repeat the experiment in the
> article cited. I will add features
> that explore system integration questions
> going to what may prove to be the 'next
> generation' of OBAM aviation electrical system
> architectures.
>
> Bob . . .
>
Message 10
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| Subject: | Re: Speaking of LiFePo4 |
Commercial Off The Shelf
Sent from my iPad
> On Jun 12, 2020, at 6:25 PM, Ken Ryan <keninalaska@gmail.com> wrote:
>
> =EF=BB
> Okay, 20 minutes with google reveals plenty of examples of COTS chargers, b
ut no definition of COTS. Could someone please educate me on this terminolog
y? Thanks.
>
Message 11
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| Subject: | Re: Z101 with Rotax 915iS |
The Rotax 912iS engine has two generators.
Generator A 16 Amp is for engine only.
Generator B 30 Amp is for aircraft electrical system.
If generator A fails, generator B automatically takes over engine duties,
but no longer supplies the aircraft electrical system.
If generator B also fails, the pilot may operate a switch to
operate the engine using aircraft battery power.
--------
Joe Gores
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=496806#496806
Message 12
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| Subject: | Re: Z101 with Rotax 915iS |
It seems to me that, even though it does not allow you to strictly follow
the new and improved Z101, the standard Rotax 915iS (two alternators +
battery) offers good redundancy. What is it about that set up that you find
lacking?
Ken
On Fri, Jun 12, 2020 at 2:54 PM Matthew S. Whiting <m.whiting@frontier.com>
wrote:
> m.whiting@frontier.com>
>
> This is my first post to the mailing list so hopefully I get it reasonabl
y
> right. I am not sure if this best fits this list or the Rotax engine lis
t,
> but will start here.
>
> For context, I am a retired CS/EE and about to start my first home built
> project. My RANS S-21 is scheduled to ship in July. I plan to use a Rot
ax
> 915iS engine and am looking now at electrical system and avionics.
>
> I have read the Connection book and perused some of the newer Z
> architectures at the web site. I am leaning towards a Z101 configuration
> as the baseline, but the problem is that the Rotax comes with only one
> generator (I know it has two, but I believe the small one is only availab
le
> to run the engine and not available for ship=99s power). Rotax sel
ls an
> external alternator kit, but a quick tally of the parts shows the cost to
> be north of $2,000 and I see nothing yet in the aftermarket.
>
> So, I am curious as to whether anyone here has installed a 915iS and, if
> so, what electrical system architecture did you choose. And, is anyone
> aware of alternative way to add a second alternator/generator to a 915iS
or
> is the Rotax option the only game in town?
>
> My second choice is a second battery to back up the avionics and engine
> should the unthinkable happen and both alternators fail and the primary
> battery not have enough reserve to get to a safe landing site. I
=99d much
> rather have a second alternator than a second battery, but $2,000 seems a
> little steep for an alternator that likely will never get used and a seco
nd
> battery at least has the advantage of extra starting reserve on our cold
> winter days in northern PA.
>
> Regards,
> Matt Whiting
>
> Sent from my iPad
>
===========
===========
===========
===========
===========
>
>
Message 13
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| Subject: | Re: Physical construction of Z101 engine bus & |
battery bus
I was simply addressing the question as posed, at least my understanding of t
he question. It seemed to be suggesting that one battery replaced every 2 y
ears was more reliable than two batteries each replaced every 4 years since o
n average the one battery was newer than the combination of the two. I don
=99t think that is a correct assumption.
I certainly would take two alternators and one battery over one alternator a
nd two batteries as well, and that is a scenario I posted earlier today in r
egards to my soon to arrive S-21 kit and 915iS engine. Unfortunately, of th
e two generators in the 915iS, it appears that only one is actually accessib
le for non-engine power supply. So, that configuration actually needs 3 in o
rder to have two available for pitot heat, lights, avionics, etc.
However, I would take two batteries (alternated every other year) and one al
ternator over one battery (new every 2 years) and one alternator.
Matt
> On Jun 12, 2020, at 6:55 PM, Charlie England <ceengland7@gmail.com> wrote:
>
> =EF=BB
> I think that when doing failure analysis, you don't really pay that much a
ttention to odds; you play 'what if'. (Actually, 'when it fails'; the assump
tion when doing failure analysis is that anything we can back up *will* fail
). You do have to take uncontrollable stuff out of the equation; we can't ca
rry an extra set of wings, for instance, and most of us accept the risk of a
single engine, in order to be able to fly at all.
>
> Once that's out of the way, then 'what if' starts. What if the alternator f
ails? It's taken off line and battery backs it up. What if the battery fails
? It's taken off line and the alternator backs it up (contrary to popular in
ternet lore). If the engine isn't electrically dependent and we're VFR with n
av on our phone, we don't even care about backup at all. The what if of both
failing in a single flight is considered to be so unlikely that most are wi
lling to treat a double failure like a wing or other structural failure; we
're just not going to go there.
>
> My personal choice with a high-amps-need engine control system is to not a
ccept the limited and continuously decreasing duration (capacity) of a stand
ard battery, nor to accept the weight penalty of a much bigger battery or mu
ltiple batteries, in order to keep the engine running to the end of the flig
ht. For me, that only leaves the choice of dual alternators.
>
> FWIW,
>
> Charlie
Message 14
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| Subject: | Re: Speaking of LiFePo4 |
Thanks!
On Fri, Jun 12, 2020 at 2:21 PM C&K <yellowduckduo@gmail.com> wrote:
>
> Commercial Off The Shelf rather than custom made
>
> On 12/06/2020 3:45 PM, Ken Ryan wrote:
> > Okay, 20 minutes with google reveals plenty of examples of COTS
> > chargers, but no definition of COTS. Could someone please educate me
> > on this terminology? Thanks.
> >
> >
>
>
Message 15
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| Subject: | Re: Z101 with Rotax 915iS |
All accurate Joe. But I think there is a wrinkle. It is my understanding
that if Gen A fails, AND the Emergency Power Switch is closed, THEN Gen B
will operate both Engine and power the Bus. At least that's my
understanding.
On Fri, Jun 12, 2020 at 4:31 PM user9253 <fransew@gmail.com> wrote:
>
> The Rotax 912iS engine has two generators.
> Generator A 16 Amp is for engine only.
> Generator B 30 Amp is for aircraft electrical system.
> If generator A fails, generator B automatically takes over engine duties,
> but no longer supplies the aircraft electrical system.
> If generator B also fails, the pilot may operate a switch to
> operate the engine using aircraft battery power.
>
> --------
> Joe Gores
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=496806#496806
>
>
Message 16
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| Subject: | Re: Z101 with Rotax 915iS |
Yes, that is my understanding. My desire though is to have two alternators available
for the aircraft electrical system. The question is: is there an economical
way to do that? The Rotax way appears to cost at least $2,000. Which I
probably will suck it up and do if there is no other way as I plan to fly IFR
and I like to have good backup not just for a comm radio and transponder, but
also pitot heat at least and that generally takes some juice. Although, I think
the Garmin regulated pitot should be a fair bit more efficient unless it is
really cold out.
Sent from my iPad
> On Jun 12, 2020, at 8:31 PM, user9253 <fransew@gmail.com> wrote:
>
>
> The Rotax 912iS engine has two generators.
> Generator A 16 Amp is for engine only.
> Generator B 30 Amp is for aircraft electrical system.
> If generator A fails, generator B automatically takes over engine duties,
> but no longer supplies the aircraft electrical system.
> If generator B also fails, the pilot may operate a switch to
> operate the engine using aircraft battery power.
>
> --------
> Joe Gores
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