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Erich_Weaver(at)URSCorp.c
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Posted: Tue May 10, 2011 9:17 am Post subject: lithium batteries

I would like to hear your Bob's or other folks comments about aviation use of the lithium batteries supplied here: 

 

http://www.lithiumaviationbattery.com/index.html

  

they seem to offer signficant weight reduction 

 

thanks 

Erich Weaver

  [quote][b]

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jan_de_jong(at)casema.nl
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Posted: Tue May 10, 2011 9:45 am Post subject: lithium batteries

This has been discussed two months ago: see archives "Shorai".

I don't think I could add anything.



Jan de Jong

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mike(at)aeromotogroup.com
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Posted: Tue May 10, 2011 2:57 pm Post subject: lithium batteries

I asked a similar question a few months back on the Lancair Mailing List and

was insulted for suggesting LiFePO4 batteries even be considered for

experimental aircraft use.  At the time I was not aware of anyone selling

them specifically for aircraft, so that's an interesting new development.



Below, I share the tactful wisdom of Mr. Regan for the benefit of all.



Michael



"Michael writes:  <<I never claimed to be an expert>>



Then perhaps you would be wise to take the council of someone who IS

experienced.



<<The SECOND link in my post is a thread with several hundred posts on

designing, building, and testing cells.  Have any of the naysayers read the

thread, in depth, or done similar research?  >>>



Wow. Reading the anecdotal results of anonymous hobbyists is not "research",

it is entertainment (for some). Reading about or doing actual experiments

with the appropriate equipment and collecting reliable and repeatable data

is research. My income depends on doing quality R&D so I appreciate the

danger of searching the internet for data that supports your position and

then taking that as evidence you are right. You can find supporting

information for ANY position on the internet.



<<< I also have read <snip> that deep discharging, such as Hamid had done,

is different than the minimal discharge we would expect from an engine

start.  The small discharge contributes to less need to balance the cells.

Quite different from the total-loss system in an RC or solar-powered

environment.>>>



Wrong, wrong and wrong.



The Wave Glider had a 10 -30 day (depending on payload power) "no sun"

duration so it was a mixed cycle, not deep discharge.



Engine start is not a minimal discharge event. A 300 amp load for 30 seconds

represents about a third of the available energy at those rates from a

typical 20 AH battery. (careful, I set a trap here)



Cell imbalance is a function of the number of charge / discharge cycles, the

depth of discharge / charge, the rate of discharge / charge, the

temperature, and cell initial "matching". If you start with matched and

balanced cells it will take longer to require balancing. Rate is one of the

more important factors because it also effects temperature due to I^2R

losses. Double the current and you get four times the heat.



<<<I'm an experimenter.  I can't just sit on the sidelines and wait for

"someone else" to do the research, testing and development, then jump on the

bandwagon.  That's why I'm building an experimental aircraft.  I thought

this forum would be a good place to discuss development and testing of new

systems rather than quickly declare it "too risky" for intelligent

discussion.>>>>



I am all for experimentation, just not at 10,000 feet with peoples lives at

stake. I have been a contributor on this list since the beginning and I have

assisted the NTSB with several accident investigations where people died

because the pilot ignored fact in favor of their own "opinion".  Flying is

serious business. Lithium batteries are sensitive to mishandling. Neither

tolerates ignorance or arrogance well.



Lithium batteries can and have been used in aerospace applications

successfully but it requires a careful, detailed and intelligent design to

mitigate the risks to an acceptable level. The risk levels that can be

tolerated for an EV motorcycle or car are significantly higher than for a

manned aircraft.



The word "Experimental" in Experimental Aircraft is not a directive to take

foolish risks. It does mean that you and you ALONE, as a pilot and builder,

are responsible for operating AND building an aircraft that is SAFE.



If I am not "intelligent" for pointing this out, so be it.



Regards

Brent Regan"



--

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 10, 2011 4:34 pm Post subject: lithium batteries

At 01:13 PM 5/10/2011, you wrote:



  	  Quote: 	
		  I would like to hear your Bob's or other folks comments about aviation use of the lithium batteries supplied here: 



   http://www.lithiumaviationbattery.com/index.html

 

 they seem to offer signficant weight reduction 	


    Yes, among other things. Quoting from the website:



 If your reading this; you already know that the primitive lead acid battery is going the way of the horse and buggy.



    . . . yeah . . . sort of.



    I can tell the List that there are a whole lot of folks

    intently interested in exploring alternatives to the

    legacy lead-acid battery technologies for a host

    of applications, not the least of which are aircraft.



    I've been indirectly and directly involved in battery

    studies for general aviation for over 10 years . . .

    and I can tell you nobody at any of my former places

    of employment are looking to go lithium as the standard

    battery product . . . yet.



    A variety of new-wave technologies have come and gone.

    Some proved useful in certain specialty applications

    such as portable power for computers, cameras, phones,

    etc. Most of these applications did not demand hi cranking

    currents to start engines nor were they expected to

    work at cold temperatures. Further, in small energy

    demand applications, the extra electronics needed to

    optimize battery performance was not a big cost of

    ownership burden. Looking at the website we see the

    following data table:



 BATTERY SIZING - 12V & 24V 



 Based on your  starter cranking   current.



 Rectangular Dimensions

 Ah           Wt./lb     CCA     w heat shrink cover   $$ (12V )

 2p, 4.6      1.7        200       4.5 x 2.2 x 3.3        200

 3p, 7.0      2.3        300       4.5 x 3.5 x 3.3        300

 4p, 9.2      3.0        400       4.5 x 4.8 x 3.3        400

 5p, 11.5     3.5        500       4.5 x 6.0 x 3.3        500

 6p, 13.8     4.0        600       4.5 x 7.2 x 3.3        600

 7p, 16.1     4.5        700       4.5 x 8.4 x 3.3        700



    I see no mention of battery selection criteria based

    on a load analysis for the endurance mode of operation.

    Keep in mind that there have been several "gee-whiz" battery

    offerings in the past that would crank an engine. I think

    some products featuring 2 a.h. jelly-roll NiCd technology

    about the size of a c-cell.



    The product even made it into the over the counter market in

    the form of a "Start Stick" sold by Sears as I recall.



    Cranking the engine is a concern only for the first

    few seconds of the day's operations. How about the rest

    of the time?



    A minimum battery that would crank your Lycoming might

    weigh in at 3 pounds and cap check at 9.2 a.h., but how

    long would that battery run your e-bus? Okay, you've got

    Z13/8 and the endurance loads are not an issue. How many

    18 a.h. SLVA batteries can you buy for $400? Let's say

    5 batteries. In a situation where the e-bus is supported

    by a second alternator, then you might get 2-3 years

    service life out of an SVLA. Let's say 2 years x 5 batteries

    gives you 10 years. The cost of ownership for 5 batteries

    is equal to that of 1 Lithium battery that has a warranty

    of 5 years and is a somewhat unknown player in the market

    when 10 years is the target service life.



    Okay, it's 15 pounds lighter than the SLVA. That's 2.5

    more gallons of fuel. Are you going to fit your airplane

    with larger tanks? Probably not. Okay, no help on fuel.

    Are you going to miss that 15 pound reduction in baggage

    limits? Hmmm . . . at 10 gph you'll be back under gross

    limits in 15 minutes after takeoff . . . doesn't seem

    like much of a worry there either.



    Suppose you don't have the second alternator and you

    really want 12+ a.h. of endurance bus support for

    alternator-out ops. Now we're talking about a $600-

    $700 battery. That will buy a LOT of SLVA capability.



    How about service life? At least with the SLVA, you're

    starting with a clean slate every two years. You're

    COMMITTED to living with the lithium product for a

    whole lot longer than that.



    The point is that until one has considered ALL the

    data points that drive a battery selection decision,

    getting sucked down the whirlpool of lighter, stronger,

    sexier, etc. etc. may keep you from making good decisions

    that tend to ditch proven technologies with no surprises

    and very predictable cost of ownership numbers.



    If you're selecting a battery for Voyager, it took about

    5 pounds of fuel to carry 1 pound of airplane around the

    world. So 15 pounds of battery would translate to 75 pounds

    of fuel. Uncle Bert MIGHT have been interested in the

    Lithium products back then. I suspect that once the RV

    builder has considered issues of weight, endurance mode

    support, cost of ownership over the LIFETIME of the

    airplane, and cold weather ops . . . that stoggy ol'

    SVLA still has a few things going for it.



    Yes, these are experimental airplanes. The owners of



 [img]cid:.0[/img]

    are out to show the world a 'better mousetrap' and I do

    wish them well. But if I were flying an RV, I'd do it to

    have fun while minimizing cost of ownership and meeting

    specific design goals. Please make sure ALL of your goals

    are identified, prioritized and considered in your battery

    selection decisions.



    It may well be that 10 years from now, everybody will

    be scoffing at the occasional SLVA hanger-on. I hope

    that the technology and market positions will have matured

    sufficiently to make that a reality. But that's not today

    folks.



 

   Bob . . .

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nuckolls.bob(at)aeroelect
Guest

Posted: Tue May 10, 2011 5:04 pm Post subject: lithium batteries

At 06:53 PM 5/10/2011, you wrote:

 	  Quote: 	
		  

<mike(at)aeromotogroup.com>



I asked a similar question a few months back on the Lancair Mailing List and

was insulted for suggesting LiFePO4 batteries even be considered for

experimental aircraft use.  At the time I was not aware of anyone selling

them specifically for aircraft, so that's an interesting new development.



Below, I share the tactful wisdom of Mr. Regan for the benefit of all.



Michael


	




   Brent's misgivings about lithium aboard airplanes are

   well founded. There IS a TSO document in place for

   FAA approval of lithium batteries. It's based in part

   on performance we've come to know and love from lead-acid

   technologies. At the same time, it acknowledges

   elevated risks for what I've suggested is akin to

   teaching your Lycoming to burn nitroglycerine. The

   energy content is spectacular but the firewalls needed

   to keep that dragon caged are significant.



   We didn't have battery fires until the wet Ni-Cad

   came along. Those dragons proved meddlesome too but

   were eventually brought to heel. Integration of

   lithium into the every day lives of the consumer-citizen

   will be an even greater challenge.

   Bob . . .

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