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Unvented AGM?

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bakerocb

Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

Posted: Wed Feb 09, 2011 5:36 am Post subject: Unvented AGM?

2/9/2011



Hello Fellow Builders, Ray St-Laurent wrote: "......an unvented AGM ......"



One could debate the difference between a valve and a vent, but it might be 

a bit misleading to describe the valve equipped AGM batteries as being 

unvented. See here:



http://en.wikipedia.org/wiki/VRLA_battery



'OC' Baker Says: "The best investment we can make is the time and effort to 

gather and understand knowledge."



===========================================================



Time: 05:10:25 AM PST US

Subject: Re: Battery box being demanded

From: "RayStL" <raystl(at)nbnet.nb.ca>

An STC of an equivalent installation might be the easiest way to convince. I 

think

that would be an unvented AGM inside the cabin.  I see there are some under

seat Cub STC's that might do. Does anyone have details. If so then I just 

need

to convince him that my battery is equivalent to that specified.

--ray



--------

Ray St-Laurent

701/Pegastol wings/Suzuki engine

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nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 09, 2011 7:08 am Post subject: Unvented AGM?

At 08:30 AM 2/9/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: <bakerocb(at)cox.net>



 2/9/2011



 Hello Fellow Builders, Ray St-Laurent wrote: "......an unvented AGM ....."



 One could debate the difference between a valve and a vent, but it might be a bit misleading to describe the valve equipped AGM batteries as being unvented. See here:



  http://en.wikipedia.org/wiki/VRLA_battery 	


    EXCELLENT point. It might also be useful to

    note that VLRA batteries (unlike VENTED wet

    batteries) are approved for shipment in the

    mails and by ordinary commercial air freight

    without benefit of extra-ordinary packaging.



    I quote here 49 CFR 173.159(d):



 (d) A nonspillable wet electric storage battery is excepted from all other requirements of this subchapter under the following conditions: (1) The battery must be protected against short circuits and securely packaged; (2) For batteries manufactured after September 30, 1995, the battery and the outer packaging must be plainly and durably marked NONSPILLABLE or NONSPILLABLE BATTERY; and (3) The battery must be capable of withstanding the following two tests, without leakage of battery fluid from the battery: (i) Vibration test. The battery must be rigidly clamped to the platform of a vibration machine, and a simple harmonic motion having an amplitude of 0.8 mm (0.03 inches), with a 1.6 mm (0.063 inches) maximum total excursion must be applied. The frequency must be varied at the rate of 1 Hz/min between the limits of 10 Hz to 55 Hz. The entire range of frequencies and return must be traversed in 955 minutes for each mounting position (direction of vibrator) of the battery. The battery must be tested in three mutually perpendicular positions (to include testing with fill openings and vents, if any, in an inverted position) for equal time periods.



    That's a rather lengthy list of requirements

    that the OBAM aircraft builder shouldn't

    have to "prove" . . . but it illustrates

    the point that cells with no loose liquid

    that are not open to atmosphere have been

    demonstrated benign for all hazards short

    of gross damage.



    In normal or even abusive service, they cannot

    produce the hazards we used to associate with

    their liquid electrolyte ancestors. All of the

    legacy hazards calling for extra containment

    of gasses/liquids simply went away.



 

   Bob . . .    [quote][b]

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RayStL

Joined: 22 Oct 2006
Posts: 36

Posted: Wed Feb 09, 2011 9:59 am Post subject: Re: Unvented AGM?

Thanks for the references guys. 

I believe there are some AGM batteries that have a 'vent' port designed to connect to a vent tube from an existing flooded cell battery box. The 'sealed' models with no port are most relevant to my situation.



--ray

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_________________
Ray St-Laurent
701/Pegastol wings/Suzuki engine

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 09, 2011 10:52 am Post subject: Unvented AGM?

At 12:59 PM 2/9/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "RayStL" <raystl(at)nbnet.nb.ca>



 Thanks for the references guys. 

 I believe there are some AGM batteries that have a 'vent' port designed to connect to a vent tube from an existing flooded cell battery box. The 'sealed' models with no port are most relevant to my situation. 	


   That 'vent' tube can be misleading. The VRLA

   is not a dry or gell battery. Liquid electrolyte

   is totally contained by capillary action in the

   fiberglas matting. When these batteries are

   abused (severe overcharge or discharge) heating

   internal to the cells will boil water and over-

   pressure the valve such that excess pressure is

   allowed to vent.  So-called, "sealed" batteries

   are sealed only to the extent of the pressure

   relief setting of the valves in the vent holes.



 

   The sum total of vented gasses is very small

   in comparison with the kind of emissions one could

   get from the classic, vented wet battery.



   When the battery is abused to a degree that

   opens the valves, there is still no liquid

   water-acid emitted, only the mix of gasses

   disassociated from the small amount of

   water in the mat. There is a very tiny risk

   for explosion if the battery is mounted in

   an airtight container. The risk is not from

   BATTERY explosion but ignition of the escaped

   gasses not allowed to waft away in the

   local breeze.



   I think we hand some discussions here on the

   List years ago where I related my experience

   with a close call for having induced injury

   or worse to a customer who was using a design

   of mine that contained a VRLA battery. I also

   discussed an incident involving a BATTERY

   BOX explosion in a GlasAir.



   Had EITHER of these batteries been fitted with

   a vent-manifold and a tube leading overboard,

   it's a certainty that these two events would

   not have unfolded so violently. But be aware

   that such vent tubes have NOTHING to do with

   the conducting corrosive liquids overboard

   and everything to do with reduced risk for

   explosion. When a VRLA battery is fitted with

   a vent-tube fitting, the tube can only serve

   to collect all the gasses from cell vents during

   an over-pressure event. Functionally, the batteries

   are no more "sealed" or "vented" than their

   other commercial contemporaries.



   Identical risk reduction is achieved by

   not wrapping an SLVA battery up in an airtight

   enclosure.



   See:



  http://tinyurl.com/5v7f9gl



 

 

   Bob . . .    [quote][b]

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RayStL

Joined: 22 Oct 2006
Posts: 36

Posted: Wed Feb 09, 2011 11:44 am Post subject: Re: Unvented AGM?

Hi Bob



You might find this amusing. It is an excerpt of a message from the DOT inspector where he cherry picks words from the Power Sonic manual. The underlines are his.



 	  Quote: 	
		  Given the right set of circumstances, such as extreme overcharging or shorting of the battery, these gases might vent into the enclosure and create the potential for an explosion when ignited by a spark. Generally, ventilation inherent in most enclosures is sufficient to avoid problems. 



Potential hazards are present, as described by the battery Manufacturer, Power-Sonic. These hazards reflects a requirement to enclose the battery in a vented battery box to ensure aviation safety for other than "During normal operation". 	




He also knows I have ‘crowbar’ overvoltage protection so extreme overcharging is not possible.



--ray

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_________________
Ray St-Laurent
701/Pegastol wings/Suzuki engine

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 10, 2011 7:22 am Post subject: Unvented AGM?

At 02:44 PM 2/9/2011, you wrote:

 --> AeroElectric-List message posted by: "RayStL" <raystl(at)nbnet.nb.ca>



 Hi Bob



 You might find this amusing. It is an excerpt of a message from the DOT inspector where he cherry picks words from the Power Sonic manual. The underlines are his.



 Given the right set of circumstances, such as extreme overcharging or shorting of the battery, these gases might vent into the enclosure and create the potential for an explosion when ignited by a spark. Generally, ventilation inherent in most enclosures is sufficient to avoid problems.



    . . . the corollary to the last statement is that

    you can't get any better ventilation than to have

    no enclosure whatsoever.



    Some months ago we were considering this particular

    example of a 'battery failure'.



  http://aeroelectric.com/Pictures/Batteries/Odyssey_OV/Odyssey_OV_1.jpg

 

    Some folks jumped on the swollen case and decided

    that what ever value the over-pressure protection

    was set for, this photo proved that it was "too low."



    The investigator did tests on the un-damaged over-pressure

    safety valves and found them well in specification.

    The observed swelling was a function of heating plus

    swelling of the battery's innards long after the

    moisture had departed the battery though the valves.



    This failure mode indicates a PROTRACTED exposure to

    an overvoltage condition by a power source capable of

    considerable energy (60+ amp alternator?). But this

    poor puppy was never at risk for root cause of any

    sort of 'explosion'.



 Potential hazards are present, as described by the battery Manufacturer, Power-Sonic. These hazards reflects a requirement to enclose the battery in a vented battery box to ensure aviation safety for other than "During normal operation".



    He is demonstrably oblivious of the finer points of

    how this new technology functions . . . and how it

    behaves when driven to failure.



    I used to have a VERY good working relationship with

    a lady who worked at the Navy's battery testing facilities

    in Crane, Indiana. I don't recall what her job title

    was . . . maybe never knew it. But she had been there

    a long time and observed a great deal of the proceedings

    in her facility with interest and understanding. Best

    yet, she was willing to share.



    I can recall conversations that might have lasted

    HOURS. She was a encyclopedia of first-hand information

    about the past, present and future of battery technologies.

    You think the FAA has an inordinate interest in

    behaviors of batteries under duress, you should hear

    what the Navy expects!



    The last time we talked, I had to call her at

    home where she was under hospice care for a terminal

    bout of cancer. I was glad I could inform her of a very

    high stature amongst many of my valued teachers.



    It's a disturbing observation that so many individuals

    with power over our lives are so ill prepared to

    execute those jobs with reason and competence. It

    follows that the execution of those duties do not

    add value . . . and in fact tax value out of our

    willingness and ability to do the best we know how

    to do.  We all wish you good fortune . . .



 

 

   Bob . . .     [quote][b]

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