Today's Message Index:
----------------------
1. 01:39 AM - Re: Re: Li-Ion Batteries for aircraft (Robert L. Nuckolls, III)
2. 05:57 AM - Re: Re: Li-Ion Batteries for aircraft (Ernest Christley)
3. 06:33 AM - Re: Re: Li-Ion Batteries for aircraft (Charlie England)
4. 09:35 AM - Re: Anyone done Bob Nuckoll's CBA modifications? (Robert L. Nuckolls, III)
5. 10:01 AM - Re: Re: Li-Ion Batteries for aircraft (Terry Watson)
6. 11:32 AM - Re: Re: Li-Ion Batteries for aircraft (Christopher Barber)
7. 12:24 PM - Re: Re: Li-Ion Batteries for aircraft (Robert L. Nuckolls, III)
8. 09:33 PM - Re: Anyone done Bob Nuckoll's CBA modifications? (CamLight)
9. 11:36 PM - Re: Re: Li-Ion Batteries for aircraft (Dave Leikam)
Message 1
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| Subject: | Re: Li-Ion Batteries for aircraft |
At 09:02 AM 12/23/2008, you wrote:
><echristley@nc.rr.com>
>
>Robert L. Nuckolls, III wrote:
>>
>> A friend of mine made this anecdotal observation about
>> batteries in the numerous crashes he investigated: He
>> said that if the airplane didn't burn after impact, more
>> often than not, the battery was pitched out and could
>> be found in the weeds. If the airplane did burn, more
>> often than not, the battery was still in the airplane.
>
>We're way off topic right now, but...huh?
How so? The discussion was about the extra-ordinary
capabilities of Li-Ion batteries that make their
acceptance into aircraft problematic. While their
energy/weight ratios and exceedingly low source
impedance make them electrically attractive, they're
also famous throughout the family of Li-Ion products
for spectacular and unpleasant failure modes from
within.
Even after these batteries are blessed by those who
know-more-about-airplanes-than-we-do, there are still
considerations for system integration which includes
crash safety.
>Are you saying that retaining the battery increases the chances of a fire?
Doesn't that stand to reason? Fires need ignition sources
and aluminum is not hard-sparking material. Hot engines are
not even particularly strong ignition sources . . . but
a battery capable of thousands of amps of fault current
could probably be demonstrated to light off magnesium castings
under the right conditions. Lighting off fuel spills is
easy.
> The takeaway being that the battery isn't our friend during/after
> an accident?
Would you not share that conclusion with me? Except for
the chance that you might sit in the wreck and use the
battery to power your radios for the purpose of calling
for help, of what practical value is it? Once the airframe
is compromised to the extent that the battery is subject to
high current discharges, it's easy to assume that fuel
tanks are equally compromised. All things considered, if
I were on short-final to the rocks, being able to eject
the battery is not an unattractive idea.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 2
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| Subject: | Re: Li-Ion Batteries for aircraft |
Robert L. Nuckolls, III wrote:
> The takeaway being that the battery isn't our friend during/after an
> accident?
>
> Would you not share that conclusion with me? Except for
> the chance that you might sit in the wreck and use the
> battery to power your radios for the purpose of calling
> for help, of what practical value is it? Once the airframe
> is compromised to the extent that the battery is subject to
> high current discharges, it's easy to assume that fuel
> tanks are equally compromised. All things considered, if
> I were on short-final to the rocks, being able to eject
> the battery is not an unattractive idea.
>
Oh, I agree. It is just not something I've ever heard discussed, or
even considered. Now I'm wondering if there are any designs that
provide for an battery eject? Considering the logic behind your
statement, the the crash investigator you referred to earlier, why
aren't there more?
Message 3
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| Subject: | Re: Li-Ion Batteries for aircraft |
Robert L. Nuckolls, III wrote:
> <nuckolls.bob@aeroelectric.com>
>
> At 09:02 AM 12/23/2008, you wrote:
>> <echristley@nc.rr.com>
>>
>> Robert L. Nuckolls, III wrote:
>>>
>>> A friend of mine made this anecdotal observation about
>>> batteries in the numerous crashes he investigated: He
>>> said that if the airplane didn't burn after impact, more
>>> often than not, the battery was pitched out and could
>>> be found in the weeds. If the airplane did burn, more
>>> often than not, the battery was still in the airplane.
>>
>> We're way off topic right now, but...huh?
>
> How so? The discussion was about the extra-ordinary
> capabilities of Li-Ion batteries that make their
> acceptance into aircraft problematic. While their
> energy/weight ratios and exceedingly low source
> impedance make them electrically attractive, they're
> also famous throughout the family of Li-Ion products
> for spectacular and unpleasant failure modes from
> within.
>
> Even after these batteries are blessed by those who
> know-more-about-airplanes-than-we-do, there are still
> considerations for system integration which includes
> crash safety.
>
>> Are you saying that retaining the battery increases the chances of a
>> fire?
>
> Doesn't that stand to reason? Fires need ignition sources
> and aluminum is not hard-sparking material. Hot engines are
> not even particularly strong ignition sources . . . but
> a battery capable of thousands of amps of fault current
> could probably be demonstrated to light off magnesium castings
> under the right conditions. Lighting off fuel spills is
> easy.
>
>> The takeaway being that the battery isn't our friend during/after
>> an accident?
>
> Would you not share that conclusion with me? Except for
> the chance that you might sit in the wreck and use the
> battery to power your radios for the purpose of calling
> for help, of what practical value is it? Once the airframe
> is compromised to the extent that the battery is subject to
> high current discharges, it's easy to assume that fuel
> tanks are equally compromised. All things considered, if
> I were on short-final to the rocks, being able to eject
> the battery is not an unattractive idea.
>
>
> Bob . . .
The 1st thing I thought about when reading the 'pitched battery=no fire'
story is, wouldn't it be fairly simple to design a G-activated
disconnect mounted directly to the battery? Basically the inverse of an
ELT activator, to fail off instead of fail on. Something as simple as a
spring- or mechanical fuse-loaded pivoting base for the battery that
would allow the top to move forward, and bolt-on bullet or blade style
connectors for the battery terminals that would face aft. With spring
loaded insulators that would close if the connector halves separate, and
the wires behind the battery and locked to structure, most any crash
impact should try to move the battery forward, 'pulling the plugs' &
allowing the insulators to close.
This wouldn't be the simplest project for a homebuilder, but should be
relatively easy for an R&D department. Also, having been in a car wreck
where the battery moved against the frame & was burning through the
steel, there might even be an opportunity to make some money if it's
marketed to auto regulators (never get it adopted voluntarily, of course).
Charlie
Message 4
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| Subject: | Re: Anyone done Bob Nuckoll's CBA modifications? |
At 10:35 PM 12/23/2008, you wrote:
>I have used the West Mountain unit a few times. No worries. I
>didn't know there was a mod. I bought mine about a year ago and
>have used it with an 11 ah battery and a few other smaller ones. I
>am getting ready to try it out with my new Oddessy 625. Maybe in a
>week, after the holiday. I have loaded the Ver 2 software, but have
>not tried it out.
>
>Sam Hoskins
>Murphysboro, IL
><http://www.samhoskins.blogspot.com>www.samhoskins.blogspot.com
>
>
>On Tue, Dec 23, 2008 at 9:53 PM, CamLight
><<mailto:jmuchow@camlight.com>jmuchow@camlight.com> wrote:
><<mailto:jmuchow@camlight.com>jmuchow@camlight.com>
>
>Hello all,
>After seeing a few units burn out unexpectedly (including one of
>mine), I've been doing an analysis of the West Mountain Radio CBA
>II. I was wondering if anyone here had done the MOSFET switch (from
>IRL2910 to IRFP2907) detailed in Bob Nuckoll's 4/10/05 analysis of
>the CBA II? Thanks!
I own 2 of these devices. The first was damaged
when I tried to do a 4a discharge on a 24v battery
(well within the rated 100W power handling capability
of the CBA II). After a determination that the
active power load transistor had shorted, I jury-rigged
a pair of FAT transistors onto an external heat
sink and secured enough functionality to complete the
task at hand. It was not intended to be a modification
to upgrade the device. I subsequently purchased a
second unit and I've been using both for a several
years.
I had some discussions with the head-shed at
West Mountain Radio about the marginal design
as demonstrated by my experience. The fellow seemed
to believe I was the only one who was having any
sort of problem and offered to repair mine under
warranty. I'd chopped and hacked it so didn't feel
like I was worthy of a warranty action. I ultimately
replace the jury-rigged "fix" with a slightly
more robust FET in the TO220 package. Both of my
cap-meters have performed as advertised since
on 12v or smaller batteries.
I'm having trouble recalling how my "mod" got
loose in the wild. I don't recall posting it to
my website but I may have shared a picture and
text with someone who has passed it along. Over
the years, I've had several inquiries about my
"mod" wherein I was unable to back-track the
information trail.
Suffice it to say that the CBA-II performs well
and as advertised on 12-volt and smaller batteries
and may well work on most batteries of higher voltage.
It's my opinion that the TO-200 case power FET used
as a load resistor is marginally applied to this
product. If I were building a similar product,
it would be more robust in this regard.
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
Message 5
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| Subject: | Re: Li-Ion Batteries for aircraft |
This is an interesting idea. It should be pretty simple in concept to design
an on-impact disconnect for a rear-mounted battery in an RV. Just allow the
battery to slide forward a few inches on impact, out of the slotted terminal
connectors mounted rigid enough to not follow the battery. RV wings have an
optional slotted mount at the leading edge to fuselage connection to allow
the wings to shear off. Someone smarter than me could probably come up with
a scheme for a firewall mounted (forward of the firewall) battery too. The
battery would still be in the airplane, but not connected to any of the
wiring.
Terry
Stalled RV-8A project (too many bright ideas; not enough consistent effort)
Seattle
-----Original Message-----
From: owner-aeroelectric-list-server@matronics.com
[mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ernest
Christley
Sent: Wednesday, December 24, 2008 5:56 AM
Subject: Re: AeroElectric-List: Re: Li-Ion Batteries for aircraft
<echristley@nc.rr.com>
Robert L. Nuckolls, III wrote:
> The takeaway being that the battery isn't our friend during/after an
> accident?
>
> Would you not share that conclusion with me? Except for
> the chance that you might sit in the wreck and use the
> battery to power your radios for the purpose of calling
> for help, of what practical value is it? Once the airframe
> is compromised to the extent that the battery is subject to
> high current discharges, it's easy to assume that fuel
> tanks are equally compromised. All things considered, if
> I were on short-final to the rocks, being able to eject
> the battery is not an unattractive idea.
>
Oh, I agree. It is just not something I've ever heard discussed, or
even considered. Now I'm wondering if there are any designs that
provide for an battery eject? Considering the logic behind your
statement, the the crash investigator you referred to earlier, why
aren't there more?
Message 6
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| Subject: | Re: Li-Ion Batteries for aircraft |
Ok, not a productive comment, however, this discussion has me playing with
the thought of hearing:
"Captain Picard, the matter/anti-matter containment is failing causing a
reaction ark, she is about to blow!"
"Geordie, eject the core....NOW!"
Yeah, I am more of a NexGen guy then TOS. To show what a geek I can be, the
"N" number on my Velocity is N17010. <g> Other Trek geeks will understand
that.
Merry Christmas all.
All the best,
Chris Barber
Houston
----- Original Message -----
From: "Terry Watson" <terry@tcwatson.com>
Sent: Wednesday, December 24, 2008 11:58 AM
Subject: RE: AeroElectric-List: Re: Li-Ion Batteries for aircraft
> <terry@tcwatson.com>
>
> This is an interesting idea. It should be pretty simple in concept to
> design
> an on-impact disconnect for a rear-mounted battery in an RV. Just allow
> the
> battery to slide forward a few inches on impact, out of the slotted
> terminal
> connectors mounted rigid enough to not follow the battery. RV wings have
> an
> optional slotted mount at the leading edge to fuselage connection to allow
> the wings to shear off. Someone smarter than me could probably come up
> with
> a scheme for a firewall mounted (forward of the firewall) battery too. The
> battery would still be in the airplane, but not connected to any of the
> wiring.
>
> Terry
> Stalled RV-8A project (too many bright ideas; not enough consistent
> effort)
> Seattle
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ernest
> Christley
> Sent: Wednesday, December 24, 2008 5:56 AM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Re: Li-Ion Batteries for aircraft
>
> <echristley@nc.rr.com>
>
> Robert L. Nuckolls, III wrote:
>> The takeaway being that the battery isn't our friend during/after an
>> accident?
>>
>> Would you not share that conclusion with me? Except for
>> the chance that you might sit in the wreck and use the
>> battery to power your radios for the purpose of calling
>> for help, of what practical value is it? Once the airframe
>> is compromised to the extent that the battery is subject to
>> high current discharges, it's easy to assume that fuel
>> tanks are equally compromised. All things considered, if
>> I were on short-final to the rocks, being able to eject
>> the battery is not an unattractive idea.
>>
> Oh, I agree. It is just not something I've ever heard discussed, or
> even considered. Now I'm wondering if there are any designs that
> provide for an battery eject? Considering the logic behind your
> statement, the the crash investigator you referred to earlier, why
> aren't there more?
>
>
>
Message 7
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| Subject: | Re: Li-Ion Batteries for aircraft |
At 07:55 AM 12/24/2008, you wrote:
><echristley@nc.rr.com>
>
>Robert L. Nuckolls, III wrote:
>> The takeaway being that the battery isn't our friend
>> during/after an accident?
>>
>> Would you not share that conclusion with me? Except for
>> the chance that you might sit in the wreck and use the
>> battery to power your radios for the purpose of calling
>> for help, of what practical value is it? Once the airframe
>> is compromised to the extent that the battery is subject to
>> high current discharges, it's easy to assume that fuel
>> tanks are equally compromised. All things considered, if
>> I were on short-final to the rocks, being able to eject
>> the battery is not an unattractive idea.
>Oh, I agree. It is just not something I've ever heard discussed, or
>even considered. Now I'm wondering if there are any designs that
>provide for an battery eject? Considering the logic behind your
>statement, the the crash investigator you referred to earlier, why
>aren't there more?
When I asked the scattered-pieces/smoking-hole crowd at RAC
to search their memories and archives for accidents where
an electrical failure figured into the chain of events leading
up to damage to aircraft/crew. They couldn't come up with
one.(*) At the same time, there were electrical issues that
caused tense moments and unplanned completions of flight.
Bottom line is that a well considered architecture, plan-A/
plan-B operating plan and reasonable training keeps even
severe electrical failures from becoming a bad day in the
cockpit. Given that OBAM aircraft are MUCH more forgiving
than Barons and Jets, electrical failures in flight are
even less risky.
I don't think there was much interest in reducing the
possibility of battery-induced, post-crash fire given that
circumstances surrounding the cases where fire did occur
were so severe that no useful difference in outcome would
have been gained if the airplane had not caught fire.
Bob . . .
(*) I've personally worked only two accidents in 30+ years
that probably started with an electrical failure. One involved
a King Air over the Swiss Alps that disappeared from radar
and radio contact . . . BEFORE traversing the peaks.
The airplane crashed into said peaks COMING THE OTHER WAY.
The prevailing theory was that the avionics master relay
failed and took down all the good stuff. The pilot decided
to return sometime after crossing the peaks and for some
reason, descended too early.
The other was loss of both alternators in a piston twin
flying in ice. Pilot made successful approach to landing
looking out the foul weather window. He lost directional
control on the runway resulting in loss of airframe and
all souls aboard.
Message 8
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| Subject: | Re: Anyone done Bob Nuckoll's CBA modifications? |
nuckolls.bob(at)aeroelect wrote:
>
> I own 2 of these devices. The first was damaged
> when I tried to do a 4a discharge on a 24v battery
> (well within the rated 100W power handling capability
> of the CBA II). After a determination that the
> active power load transistor had shorted, I jury-rigged
> a pair of FAT transistors onto an external heat
> sink and secured enough functionality to complete the
> task at hand. It was not intended to be a modification
> to upgrade the device. I subsequently purchased a
> second unit and I've been using both for a several
> years.
>
> I had some discussions with the head-shed at
> West Mountain Radio about the marginal design
> as demonstrated by my experience. The fellow seemed
> to believe I was the only one who was having any
> sort of problem and offered to repair mine under
> warranty. I'd chopped and hacked it so didn't feel
> like I was worthy of a warranty action. I ultimately
> replace the jury-rigged "fix" with a slightly
> more robust FET in the TO220 package. Both of my
> cap-meters have performed as advertised since
> on 12v or smaller batteries.
That's good news! I've heard of about 8 units that have blown their FETs and couple
that also took out the driving op-amp and some resistor/capacitors too.
I ended up using an Infineon IPP048N06L MOSFET for its great continuous rating
for use as a load (DC plot line in the SOA graph). Seems that it's both the
higher wattages and higher voltage batteries that can cause problems. Makes sense
though. The first is due to temperature and the second due to hotspotting
and thermal runaway.
nuckolls.bob(at)aeroelect wrote:
>
> I'm having trouble recalling how my "mod" got
> loose in the wild. I don't recall posting it to
> my website but I may have shared a picture and
> text with someone who has passed it along. Over
> the years, I've had several inquiries about my
> "mod" wherein I was unable to back-track the
> information trail.
Well, I can give you the trail I followed. :-)
A friend had told me about seeing an analysis of the CBA but forgot where. A Goodle
search led to an archive of a thread here on, IIRC, April 10, 2005. In that
thread you provided a link to your analysis in the Articles section of your
site. But the document was no longer there. This link though gave me the file
name and my search led to an individual who had the document available from
their site. I don't remember who.
nuckolls.bob(at)aeroelect wrote:
>
> Suffice it to say that the CBA-II performs well
> and as advertised on 12-volt and smaller batteries
> and may well work on most batteries of higher voltage.
> It's my opinion that the TO-200 case power FET used
> as a load resistor is marginally applied to this
> product. If I were building a similar product,
> it would be more robust in this regard.
>
> Bob . . .
>
I completely agree. My analysis of two CBA's was pretty extensive (43 page document)
and led me to conclude that it shouldn't be used at over 65W for long-term
reliability and 86W to prevent the MOSFET from exceeding its max rated operating
temperature. I also found out that the CBA's stock MOSFET isn't even rated
for use as a load and was susceptible to hotspotting and thermal runaway (resulting
in the MOSFET burning out) at well below the CBA's 100W rating when
discharging at higher voltages.
A MOSFET change, over to the IPP048N06L, and a fan change were the mods I made
to bring the CBA's continuous power rating up to 106W at up to 48V without worrying
about exceeding any of the MOSFET's specs. The extra fan also helped to
keep the fuse and fuseholders from dropping out of the circuit board too when
discharging at 30A or so. It happened more than once to me (and others) before
we finally found ways to cool the circuit board and fuse. Very frustrating.
:)
--------
John M.
Owner
CamLight Systems
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=221015#221015
Message 9
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| Subject: | Re: Li-Ion Batteries for aircraft |
I would consider a dual wire high current plug similar to one used on my
snowplow main power lead. The plug supplies current to a motor similar to
an engine starting motor which drives hydraulics to operate the plow. The
plug is very robust and under very harsh operating conditions has never
unplugged itself during plowing operations. The plug hangs freely between
the front bumper of my truck and the plow. However, with a good tug the
plug separates to disconnect the wires to remove the plow unit from my
truck. This could be installed in the battery connection wires of the
airplane and supported so as to disconnect in the event of excessive forward
g forces. The contact pins are also recessed in plastic so after
disconnect, there would be no chance of contact with other metal if the
battery terminals were also covered. See 4b and 4c in the link below.
http://www.rustrepair.com/snow_plow_parts/onlinecat.htm?r=ds&p=sn-boss-bs.elec
Dave Leikam
RV-10 #40496
N89DA (Reserved)
Muskego, WI
----- Original Message -----
From: "Terry Watson" <terry@tcwatson.com>
Sent: Wednesday, December 24, 2008 11:58 AM
Subject: RE: AeroElectric-List: Re: Li-Ion Batteries for aircraft
> <terry@tcwatson.com>
>
> This is an interesting idea. It should be pretty simple in concept to
> design
> an on-impact disconnect for a rear-mounted battery in an RV. Just allow
> the
> battery to slide forward a few inches on impact, out of the slotted
> terminal
> connectors mounted rigid enough to not follow the battery. RV wings have
> an
> optional slotted mount at the leading edge to fuselage connection to allow
> the wings to shear off. Someone smarter than me could probably come up
> with
> a scheme for a firewall mounted (forward of the firewall) battery too. The
> battery would still be in the airplane, but not connected to any of the
> wiring.
>
> Terry
> Stalled RV-8A project (too many bright ideas; not enough consistent
> effort)
> Seattle
>
> -----Original Message-----
> From: owner-aeroelectric-list-server@matronics.com
> [mailto:owner-aeroelectric-list-server@matronics.com] On Behalf Of Ernest
> Christley
> Sent: Wednesday, December 24, 2008 5:56 AM
> To: aeroelectric-list@matronics.com
> Subject: Re: AeroElectric-List: Re: Li-Ion Batteries for aircraft
>
> <echristley@nc.rr.com>
>
> Robert L. Nuckolls, III wrote:
>> The takeaway being that the battery isn't our friend during/after an
>> accident?
>>
>> Would you not share that conclusion with me? Except for
>> the chance that you might sit in the wreck and use the
>> battery to power your radios for the purpose of calling
>> for help, of what practical value is it? Once the airframe
>> is compromised to the extent that the battery is subject to
>> high current discharges, it's easy to assume that fuel
>> tanks are equally compromised. All things considered, if
>> I were on short-final to the rocks, being able to eject
>> the battery is not an unattractive idea.
>>
> Oh, I agree. It is just not something I've ever heard discussed, or
> even considered. Now I'm wondering if there are any designs that
> provide for an battery eject? Considering the logic behind your
> statement, the the crash investigator you referred to earlier, why
> aren't there more?
>
>
>
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