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12v supply to stabilize avionics

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n103md(at)yahoo.com
Guest

Posted: Fri Apr 27, 2007 1:10 pm Post subject: 12v supply to stabilize avionics

I am purchasing a 12V power supply that takes

6-24V input and gives 12V out at up to 14 A continuous.

It's a 95% efficient switcher with a quiescent current

around 10mA. We need to buy ten of them to get a

better price (about $55).



Why do I want one? Why might you want one?



I have a 1-battery airplane and don't want to rewire the

whole thing. The GPS and radios reboot if they are on when

I start the engine. During cranking, the bus voltage drops

to around 10 V, and the avionics brown out. I want that

problem to go away, and also want to keep the radio working

for a while if the alternator shuts down and the battery drains

below 10V.



So, the solution I am trying is a switching power supply that

converts anything between 6 and 24 V in to a stabilized 12V out.

with 95% efficiency, the lost power is minimal. We would like to

buy 10 units for about $55 each (+ s/h). We've accounted for

four units, so there will be six more available. Who wants one?



-bob mackey

 n103md -at- yahoo.com

rjquillin(at)gmail.com
Guest

Posted: Fri Apr 27, 2007 2:01 pm Post subject: 12v supply to stabilize avionics

At 14:09 4/27/2007, you wrote:

 	  Quote: 	
		  So, the solution I am trying is a switching power supply that

converts anything between 6 and 24 V in to a stabilized 12V out.

with 95% efficiency, the lost power is minimal. We would like to

buy 10 units for about $55 each (+ s/h). We've accounted for

four units, so there will be six more available. Who wants one?


	


Could you forward some additional technical specs on the unit?



tnx

mprather(at)spro.net
Guest

Posted: Fri Apr 27, 2007 3:43 pm Post subject: 12v supply to stabilize avionics

Based on previous discussions, seems like return on investment won't be

good...



When battery only (dead alternator), once the battery is down to ~11v

there's very little usable energy left.  Adding the regulated supply

wouldn't likely added but possibly a moment of additional system operation

- the input voltage will sag very quickly.  You might actually lose

operating time because of the (small) inefficiency in the supply.



To buffer the brownout condition, you might consider a couple of ideas.. 

A diode (or relay) and a "largish" cap would protect against brownouts of

relatively short duration (while the starter is cranking).  You might also

look at your wiring and take a few measurements of system voltages (at the

battery, and at the buss) while cranking (scope plots would be ideal). 

Depending on how your buss gets power, and your ground routing, you might

not be getting the highest possible voltage to the radios while cranking. 

A little rewiring might take care of most of the problem..



Let me know if you are interested in how to wire up a diode/relay and cap

to reduce the impact of brownouts..

Matt-

 	  Quote: 	
		   

 I am purchasing a 12V power supply that takes

 6-24V input and gives 12V out at up to 14 A continuous.

 It's a 95% efficient switcher with a quiescent current

 around 10mA. We need to buy ten of them to get a

 better price (about $55).



 Why do I want one? Why might you want one?



 I have a 1-battery airplane and don't want to rewire the

 whole thing. The GPS and radios reboot if they are on when

 I start the engine. During cranking, the bus voltage drops

 to around 10 V, and the avionics brown out. I want that

 problem to go away, and also want to keep the radio working

 for a while if the alternator shuts down and the battery drains

 below 10V.



 So, the solution I am trying is a switching power supply that

 converts anything between 6 and 24 V in to a stabilized 12V out.

 with 95% efficiency, the lost power is minimal. We would like to

 buy 10 units for about $55 each (+ s/h). We've accounted for

 four units, so there will be six more available. Who wants one?



 -bob mackey

  n103md -at- yahoo.com

gmcjetpilot

Joined: 04 Nov 2006
Posts: 170

Posted: Sat Apr 28, 2007 1:34 am Post subject: 12v supply to stabilize avionics

That is a hard to believe price for that power supply.

   

  What about weight?

   

  What if it fails? 

   

  Why not as suggested use a capacitor and diode?

   

  How about turn the avionics off during start with a avionics master switch?

   

  How about a more efficient starter (NL skytec), bigger starter wire and stronger battery?

   

  Good luck but sounds like more complication than necessary. Of course the aeroelectric way is more complication and weight, always good.

   

  George



   

   

   

   

  >Subject: 12v supply to stabilize avionics

 	  Quote: 	
		  From: "bob mackey" <n103md(at)yahoo.com>

  >
	


  >I am purchasing a 12V power supply that takes

 	  Quote: 	
		  6-24V input and gives 12V out at up to 14 A continuous.

It's a 95% efficient switcher with a quiescent current

around 10mA. We need to buy ten of them to get a

better price (about $55).


	


         Ahhh...imagining that irresistible "new car" smell?

 Check out [url=http://us.rd.yahoo.com/evt=48245/*http://autos.yahoo.com/new_cars.html;_ylc=X3oDMTE1YW1jcXJ2BF9TAzk3MTA3MDc2BHNlYwNtYWlsdGFncwRzbGsDbmV3LWNhcnM-]new cars at Yahoo! Autos.[/url]  [quote][b]

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 28, 2007 8:36 am Post subject: 12v supply to stabilize avionics

At 02:32 AM 4/28/2007 -0700, you wrote:



 	  Quote: 	
		  That is a hard to believe price for that power supply.


	


   Agreed



 	  Quote: 	
		  

What about weight?


	


   Devices like this don't need to be "heavy". With

   some of the new high frequency, boost-buck topology

   supplies available, this device could weigh under

   a pound.



 	  Quote: 	
		  

What if it fails?


	


   Single points of failure for lots of things

   running downstream is a consideration.

 	  Quote: 	
		  

Why not as suggested use a capacitor and diode?


	


   The ability of a capacitor to support a load is

   bounded by the relationship . . .



   A      V

---- = -----

   F      S



   This says Amps per Farad equals Volts per Second.



   Assuming "brownout" is defined a duration that a

   battery is under 9 volts, the time is rather short

   . . . on the order of 200 milliseconds or so. See:



   Here's a battery trace on an engine with a PM

   starter who's inrush drags the battery down to

   7.5 volts. In 200 milliseconds, the engine speed

   is up high enough to allow battery to rise to

   9 volts or more. Note that "cranking" is happening

   at about 10 volts. We can see that the engine starts

   on the third cylinder compression after a total

   cranking duration of 500 milliseconds.



   So assume you have a capacitor charged to battery

   voltage (12.5 according to our trace) minus a diode

   drop so we're going to start out at about 11.7 volts.

   Assume a brownout protected load of 1A. We want to

   limit the voltage sag to 1.7 volts for 500 mS plus

   headroom - lets say 1 second. One of those auto

   super audio system monster caps is readily

   available in 1 Farad sizes. 1 Farad will drop 1

   volt per second with our 1 A load.  A 1 Farad

   capacitor would support about 1.7 amps for

   1 second to keep the sag under 1.7 volts.



   If you have lighter loads, then the capacitor

   can get smaller. Assume a couple of solid state

   electro-whizzies at perhaps .2A each for total

   of 0.4A. A 1.7 volt sag over one second at

   0.4A calls for about 250,000 microfarads.



   We're talking pretty BIG hunks of hardware here.

   There are other considerations about connecting

   large capacitors across a battery fed bus . . . big

   inrush currents. When you purchase one of those

   1F capacitors (about 3" diameter, 10" long)

   the installation instructions suggest charging

   the capacitor through a resistor before connecting

   it directly to the battery.



   Now, if one chooses to diode isolate an e-bus,

   then the diode is already in place. But the

   pre-start interval where lots of things are

   already powered up puts a load on the battery

   that may have you starting out at less than

   12.5 volts hypothesized above. Further,

   the trace shows BATTERY voltage. There

   are small but perhaps significant drops elsewhere

   to consider.



   Obviously, one can stir the design goals.

   Perhaps you can live with a half second brown

   out buffer. The size of the capacitor goes down

   by half.



   Hmmmm . . . perhaps the diode isolated

   capacitor is not very practical for loads of

   more than 100 mA or so.



   Okay, you could put the stabilizing supply

   in series with the e-bus isolation diode. This

   leaves you with the e-bus alternate feed path

   to back up a possible failure of the stabilization

   supply. But I'd want to do more study about the

   potential for other problems should the e-bus

   alternate feed switch get closed during normal

   operations . . . you don't want to close a loop

   that causes the stabilization supply to attempt

   to charge the battery with the battery's own

   output.



   A stabilization supply is going to be lighter

   and smaller than a monster capacitor that will

   never have the sag-mitigation capabilities of

   the stabilization supply. How about a small,

   SVLA battery that would support the e-bus during

   cranking. A 2 a.h. battery connected to one of

   the e-bus fuses and controlled from a switch

   on the panel would be a stone-simple means for

   providing e-bus support during start-up brownout

   offers a low risk means by which one avoids

   disappointing results from more complex approaches.



   How about a battery pak of 8 d-size alkaline

   cells that are relay connected to an e-bus fuse

   when you hit the starter button. Alkalines have

   VERY long self lives, they're only needed a few

   seconds per flight cycle. The eliminate any

   need to worry about charging or extraordinary

   maintenance. You would throw a new d-pak in on

   condition . . . i.e. the first time it failed

   to cover the brown out. Sound's pretty

   attractive to me. It puts nothing in series

   with your e-bus loads and loss of performance

   does not impact any flight condition.



   The point of this dissertation is not so much

   to champion or trash any given approach. It's

   intended to be an illumination of the duties that

   engineers have to fully understand the statics and

   dynamics of their ideas as they impact design

   goals. It's not intended to discourage experimentation.

   It would be a good thing if 10 folks got together

   and tried the brown-out protection scheme being

   proposed. My role here is only to shine the

   light around and help identify things lurking

   out there in the dark that one needs to be

   watchful for during the experiment. But finally,

   how ever the experiment comes out, publish your

   findings here on the List. Letting folks know

   what does not work is more valuable some times

   that limiting your postings to things that

   do work.



   The 'complexity' arises not so much from amount

   or kinds of hardware used but from a need to

   identify, study and understand the system dynamics

   as it affects design goals. I'm working a problem

   now that arose from a hip-shot decision of a tiny

   detail of a major system change that has cost us

   about $100K a year for the last six years dealing

   with the fallout. It took six years for the

   pressure gauge to reach a point that someone of

   authority says we need to do something about it . . .

   which leaves others wailing about the $200K and

   6-10 months it's going to take to certify a fix

   that should never have been needed in the first

   place.

 	  Quote: 	
		  

How about turn the avionics off during start with a avionics master switch?


	


   If the issue is simply that some electro-whizzies

   reboot due to the brownout event, why turn them off?



 	  Quote: 	
		  

How about a more efficient starter (NL skytec),


	


   There is no study I'm aware of that shows any

   starter to be more "efficient" than another starter.

   Such claims are made but unsupported in the 4-color

   brochures for all the popular products offered.

   In fact, efficiency of a starter (h.p. out for watts

   consumed) is the last of our concerns for optimizing

   system functionality. It's how fast the engine gets

   started. If I could trade a 50% loss of absolute

   efficiency for a 50% drop in cranking time, I'd do

   it in a heartbeat.



   The starter feature under discussion here is locked-

   rotor current or inrush. It's a given that for starters

   of about the same size, the series wound starter will

   have lower inrush currents than a PM starter. This

   is a hard fact that drove B&C's decision to say with

   their original philosophy. While others (most notably

   the automotive industry) were rapidly embracing PM

   starters for lower cost, we knew that aviation was not

   so much driven by absolute cost as it was by performance

   delivered for cost.



   Until someone is ready to fund an apples for apples

   comparison of the various starters and quantify their

   relative performance numbers, the gold-plated,

   bright shining claims to market superiority of any

   electrical feature are to be taken with a grain

   of sand. Pontiac has touted a "new wider look" since

   I was a kid. If they were really meeting their marketing

   claims claims, you'd need a wide load permit by now

   just to drive one.



 	  Quote: 	
		    bigger starter wire and stronger battery?


	


   Certainly worth considering . . . but that

   inrush can be 1000 amps! Remember folks, we're

   talking about techniques to mitigate an event

   that lasts for less than one second per flight cycle.

   The obvious, low cost, maximum efficiency, minimum

   risk, minimum weight approach is to develop

   a operating procedure work-around and leave the

   hardware alone.



   Every other approach offers a requirement to

   deduce, understand, consider and then fit every

   new system integration problem into the design

   goals for the airplane. There can be a lot more

   to the task than plug-play-and-pretend that

   we've done a good thing. Man! when I think of all

   those whippy new products I could have brought

   to market with the $600K that went down the

   tubes . . .



 	  Quote: 	
		  

Good luck but sounds like more complication than necessary.


	


   Agreed.



 	  Quote: 	
		    Of course the aeroelectric way is more complication and weight, always good.


	


   Please describe any modification you would make to any

   suggestion in the 'Connection that would reduce

   weight and/or complexity. Describe also what features

   of the design goals for that suggestion one

   should be willing to give up in exchange for

   the perceived reduction in weight or complexity.

   If your claim is accurate, then a substantiation

   dissertation of underlying simple-ideas would be

   much appreciated.



   Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 28, 2007 8:39 am Post subject: 12v supply to stabilize avionics

At 02:09 PM 4/27/2007 -0700, you wrote:



 	  Quote: 	
		  

I am purchasing a 12V power supply that takes

6-24V input and gives 12V out at up to 14 A continuous.

It's a 95% efficient switcher with a quiescent current

around 10mA. We need to buy ten of them to get a

better price (about $55).



Why do I want one? Why might you want one?


	


  Put me down on the list to buy one should this

  deal move forward. I'd like to have one to play

  with on the drive stand this summer.



 	  Quote: 	
		  I have a 1-battery airplane and don't want to rewire the

whole thing. The GPS and radios reboot if they are on when

I start the engine. During cranking, the bus voltage drops

to around 10 V, and the avionics brown out. I want that

problem to go away, and also want to keep the radio working

for a while if the alternator shuts down and the battery drains

below 10V.


	


   Actually, your battery probably spends a few milliseconds

   at voltages below 8 volts . . . Actual cranking, i.e. energy

   delivered to the engine for starting does happen at about

   10 volts but there's that gawd-awful inrush before cranking

   actually beings that is the real dragon to slay.

 	  Quote: 	
		  So, the solution I am trying is a switching power supply that

converts anything between 6 and 24 V in to a stabilized 12V out.

with 95% efficiency, the lost power is minimal. We would like to

buy 10 units for about $55 each (+ s/h). We've accounted for

four units, so there will be six more available. Who wants one?


	


   ME!



   Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Sat Apr 28, 2007 10:31 am Post subject: 12v supply to stabilize avionics

Interesting thread, my 182 with a g1000 doesn't even blink during a

start-up. It's a 24volt system though. I wonder if there are fat caps in the

avionics modules that prevent any reaction to the starting load. Startups

are performed with one pfd, one com, and the rest of the avionics energized

(bus 1).

CS



--

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 28, 2007 12:04 pm Post subject: 12v supply to stabilize avionics

At 02:30 PM 4/28/2007 -0400, you wrote:



 	  Quote: 	
		  

<pilot4profit(at)sbcglobal.net>



Interesting thread, my 182 with a g1000 doesn't even blink during a

start-up. It's a 24volt system though. I wonder if there are fat caps in the

avionics modules that prevent any reaction to the starting load. Startups

are performed with one pfd, one com, and the rest of the avionics energized

(bus 1).

CS


	


   Probably not. It takes more than the simple diode-capacitor

   ploy to fool an appliance into ignoring a startup-brownout.

   Your appliances were no doubt qualified under

   DO-160 recommendations by folks who took those recommendations

   to heart and crafted products designed to live in the real

   world of airplanes.



   The absence problems manifested by other products being discussed

   in this thread is a testament to their professional responsibility

   an skills as engineers.

   Bob . . .

pilot4pay

Joined: 01 Jan 2007
Posts: 171
Location: Louisville, KY

Posted: Sat Apr 28, 2007 2:08 pm Post subject: 12v supply to stabilize avionics

--> <nuckollsr(at)cox.net>

   Probably not. It takes more than the simple diode-capacitor

   ploy to fool an appliance into ignoring a startup-brownout.

   Your appliances were no doubt qualified under

   DO-160 recommendations by folks who took those recommendations

   to heart and crafted products designed to live in the real

   world of airplanes.



   The absence problems manifested by other products being discussed

   in this thread is a testament to their professional responsibility

   an skills as engineers.

   Bob . . .



Certainly I didn't mean to suggest something that simple, but do you mean to

say that there is no other source of current other than the battery bus? I

guess what I'm getting at is would a fat cap be employed as a component of a

more sophisticated sub-system between the bus and the avionics circuitry, at

a module level or avionics bus level?

Or would something like Lion batteries be the chosen component, again, not

as a standalone thing, but as the choice component to be the current

reservoir in an engineered sub-system to keep the avionics alive.

CS

_________________
Craig Smith
CH640 builder
SN: 0078

"Just think how stupid the average person is,
and then realize that half of them are even stupider!"
--George Carlin

nuckollsr(at)cox.net
Guest

Posted: Sat Apr 28, 2007 3:03 pm Post subject: 12v supply to stabilize avionics

At 06:07 PM 4/28/2007 -0400, you wrote:



 	  Quote: 	
		  

<pilot4profit(at)sbcglobal.net>


--> <nuckollsr(at)cox.net>

    Probably not. It takes more than the simple diode-capacitor

    ploy to fool an appliance into ignoring a startup-brownout.

    Your appliances were no doubt qualified under

    DO-160 recommendations by folks who took those recommendations

    to heart and crafted products designed to live in the real

    world of airplanes.



    The absence problems manifested by other products being discussed

    in this thread is a testament to their professional responsibility

    an skills as engineers.

    Bob . . .



Certainly I didn't mean to suggest something that simple, but do you mean to

say that there is no other source of current other than the battery bus? I

guess what I'm getting at is would a fat cap be employed as a component of a

more sophisticated sub-system between the bus and the avionics circuitry, at

a module level or avionics bus level?

Or would something like Lion batteries be the chosen component, again, not

as a standalone thing, but as the choice component to be the current

reservoir in an engineered sub-system to keep the avionics alive.


	


    . . . or the power supply within the product has the

   same wide input range cited in the topic that

   started this thread. Nowadays, it's not a big

   deal to tailor input power conditioning to

   cover ALL expected inputs. On a 14v device a

   design goal might be for normal operation over

   the DO-160 11 to 16 volt suggested range,

   useable if somewhat degraded down to 9 volts

   and orderly behavior for start-up brownouts.

   I seriously doubt that anyone finds it useful

   to go for a diode-cap or internal battery unless

   a swift footed power supply is just impossible

   or impractical.



   Bob. . .

n103md(at)yahoo.com
Guest

Posted: Sun Apr 29, 2007 6:56 am Post subject: 12v supply to stabilize avionics

As Bob Nuchols surmised, this is lighter weight than

a second battery -- 0.1 lbs plus wiring.

It uses an Linear LTC3780.

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1116,P10090



The spec sheet for the 12V supply is attached.



-bob mackey

DSX12V_power_supply.pdf

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Jerry Cochran

Joined: 10 Jan 2006
Posts: 111
Location: Wilsonville, OR

Posted: Sun Apr 29, 2007 11:37 am Post subject: 12v supply to stabilize avionics

That's what I did for my GRT EFIS brownout/reboot problem. I installed a  hi-qual switch. If that switch ever fails, I have one radio, GPS and Dynon still  good. But what are the odds? Now I just do an engine start, then flip R mag,  Alternator, and Avionix switches on. Slick, and no pesky and long rebooting of  GRT.

  

 BTW, my Skytec spins the XP-IO360 like crazy from a 4 yr old PC680 Batt. I  know, Bob, I should replace it every year, but I'm VFR and cheap... 

  

 Jerry Cochran

  	  Quote: 	
		  From:    <gmcjetpilot(at)yahoo.com>

Subject: Re: 12v supply to    stabilize avionics



<snip>

   

  How    about turn the avionics off during start with a avionics master    switch?

   

  How about a more efficient starter (NL    skytec), bigger starter wire and stronger

battery?

      

  Good luck but sounds like more complication than necessary. Of    course the aeroelectric

way is more complication and weight, always    good.

   

  George

	


 

  



See what's free at AOL.com. 

  [quote][b]

nuckollsr(at)cox.net
Guest

Posted: Mon Apr 30, 2007 5:05 am Post subject: 12v supply to stabilize avionics

At 03:32 PM 4/29/2007 -0400, you wrote:



 	  Quote: 	
		  That's what I did for my GRT EFIS brownout/reboot problem. I installed a 

hi-qual switch. If that switch ever fails, I have one radio, GPS and Dynon 

still good. But what are the odds? Now I just do an engine start, then 

flip R mag, Alternator, and Avionix switches on. Slick, and no pesky and 

long rebooting of GRT.



BTW, my Skytec spins the XP-IO360 like crazy from a 4 yr old PC680 Batt. I 

know, Bob, I should replace it every year, but I'm VFR and cheap...


	


    If you have "a plan" for dealing with electrical

    system failure, there's nothing inherently wrong

    with running a battery until it croaks an won't

    start the engine any more.



    My admonition for a PM program that tracks battery

    condition by either measurement or periodic replacement

    presumes that you fly in conditions where loss of the

    system is likely to star you in a dark-n-stormy-night

    story.



    It has nothing to do with being "cheap" and everything

    to do with failure mode effects analysis: "What's

    the sweat-factor for having this part fail and what's

    the most efficient investment of $time$ to mitigate

    that condition? If you're in a no-sweat mode of

    ownership and operation, then running the battery into

    the ground IS the most efficient cost of ownership

   philosophy.



    Bob . . .

nuckollsr(at)cox.net
Guest

Posted: Mon Apr 30, 2007 5:12 am Post subject: 12v supply to stabilize avionics

At 07:55 AM 4/29/2007 -0700, you wrote:



 	  Quote: 	
		  As Bob Nuchols surmised, this is lighter weight than

a second battery -- 0.1 lbs plus wiring.

It uses an Linear LTC3780.

http://www.linear.com/pc/productDetail.jsp?navId=H0,C1,C1003,C1042,C1116,P10090



The spec sheet for the 12V supply is attached.


	




  Take a peek at the detail specs for the i.c. at:



http://tinyurl.com/399l2x



  Note that the part is rated at up to 5A continuous

  with the parts described in the application example.

  The larger currents cited are short term or momentary

  capability.

        Bob . . .



        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

Jerry Cochran

Joined: 10 Jan 2006
Posts: 111
Location: Wilsonville, OR

Posted: Tue May 01, 2007 8:33 am Post subject: 12v supply to stabilize avionics

Bob,

  

 I am in phase one testing with only 15 hrs on the system, so of course,  VFR/day only and within 50 NM radius. Before relying on this 4 yr old PC680 for  phase one though, I load tested it and was good. Begs the question though, isn't  it being "load tested" on each engine startup? Do you  advise other periodic testing?  My copy of AEC at hangar...  

  

 Of course, if/when I do nitetime ops and/or IFR, then I'll go to  a yearly mode for battery replacement. 

  

 Thanx,

 Jerry Cochran 

  

  

     If you have "a plan" for dealing with  electrical

    system failure, there's nothing inherently  wrong

    with running a battery until it croaks an won't

     start the engine any more.



    My admonition for a PM  program that tracks battery

    condition by either measurement or  periodic replacement

    presumes that you fly in conditions where  loss of the

    system is likely to star you in a  dark-n-stormy-night

    story.



    It has nothing  to do with being "cheap" and everything

    to do with failure mode  effects analysis: "What's

    the sweat-factor for having this part  fail and what's

    the most efficient investment of $time$ to  mitigate

    that condition? If you're in a no-sweat mode  of

    ownership and operation, then running the battery  into

    the ground IS the most efficient cost of  ownership

   philosophy.



    Bob . . .  



 

  



See what's free at AOL.com. 

  [quote][b]

BobsV35B(at)aol.com
Guest

Posted: Tue May 01, 2007 8:40 am Post subject: 12v supply to stabilize avionics

In a message dated 5/1/2007 11:36:03 A.M. Central Daylight Time,  Jerry2DT(at)aol.com writes:

  	  Quote: 	
		     I am in phase one testing with only 15 hrs on the system, so of course,    VFR/day only and within 50 NM radius. Before relying on this 4 yr old PC680    for phase one though, I load tested it and was good. Begs the question though,    isn't it being "load tested" on each engine startup? Do you    advise other periodic testing?  My copy of AEC at hangar...    

	


 

Good Morning Jerry,

  

 Different Bob here, but I think you will find that a battery that tests as  low as, or even lower than, ten percent of it's normal category will still crank  an engine. Proper load testing needs to be done on a regular basis as suggested  by 'Lectric Bob and others.

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



See what's free at AOL.com. 

  [quote][b]

khorton01(at)rogers.com
Guest

Posted: Tue May 01, 2007 3:41 pm Post subject: 12v supply to stabilize avionics

On 1 May 2007, at 12:39, BobsV35B(at)aol.com wrote:



 	  Quote: 	
		   In a message dated 5/1/2007 11:36:03 A.M. Central Daylight Time,  

 Jerry2DT(at)aol.com writes:

 I am in phase one testing with only 15 hrs on the system, so of  

 course, VFR/day only and within 50 NM radius. Before relying on  

 this 4 yr old PC680 for phase one though, I load tested it and was  

 good. Begs the question though, isn't it being "load tested" on  

 each engine startup? Do you advise other periodic testing?  My copy  

 of AEC at hangar...

 Good Morning Jerry,



 Different Bob here, but I think you will find that a battery that  

 tests as low as, or even lower than, ten percent of it's normal  

 category will still crank an engine. Proper load testing needs to  

 be done on a regular basis as suggested by 'Lectric Bob and others.




	


Load testing should be done, if safety depends on having a battery of  

some particular capacity.  If the consequences of alternator failure  

+ battery failure are acceptable, then there is no need to do  

periodic battery load testing.



Kevin Horton         RV-8 (finishing kit)

Ottawa, Canada

http://www.kilohotel.com/rv8

nuckollsr(at)cox.net
Guest

Posted: Tue May 01, 2007 4:08 pm Post subject: 12v supply to stabilize avionics

At 12:31 PM 5/1/2007 -0400, you wrote:



 	  Quote: 	
		  Bob,



I am in phase one testing with only 15 hrs on the system, so of course, 

VFR/day only and within 50 NM radius. Before relying on this 4 yr old 

PC680 for phase one though, I load tested it and was good. Begs the 

question though, isn't it being "load tested" on each engine startup? Do 

you advise other periodic testing?  My copy of AEC at hangar...



Of course, if/when I do nitetime ops and/or IFR, then I'll go to a yearly 

mode for battery replacement.


	


   There are two kinds of tests that one conducts on a

   battery to know "all of the story". Yes, cranking the

   engine is a non-quantified but certainly valid anecdotal

   "load test".  The tests accomplished by your local

   service mechanic with something like this . . .



http://www.aeroelectric.com/Pictures/Tools/Battery_Testers/HF91129_4.jpg



   is a quantified equivalent of the "see if she cranks"

   test.



   The other piece of data still more useful to the

   owner/operator is the CAPACITY test. "How long will

   it run the useful goodies on my panel?"



   A load test won't tell you but a cap test with this

   thing will . . .



http://www.aeroelectric.com/Pictures/Tools/CBA2_1.jpg



   If you don't want to invest $time$ in doing the periodic

   hat dance necessary for the quantified test, then you

   simple replace it long before you think it's capacity

   is compromised with age. Sometimes the periodic, blind

   replacement is more effective for reducing cost of ownership

   than detailed testing.



   Bob . . .

        ----------------------------------------

        ( IF one aspires to be "world class",  )

        ( what ever you do must be exercised   )

        ( EVERY day . . .                      )

        (                  R. L. Nuckolls III  )

        ----------------------------------------

BobsV35B(at)aol.com
Guest

Posted: Tue May 01, 2007 4:45 pm Post subject: 12v supply to stabilize avionics

In a message dated 5/1/2007 6:43:05 P.M. Central Daylight Time,  khorton01(at)rogers.com writes:

  	  Quote: 	
		  Load    testing should be done, if safety depends on having a battery of     

some particular capacity.  If the consequences of alternator    failure  

+ battery failure are acceptable, then there is no need to    do  

periodic battery load testing.



	


 

Good Evening Kevin,

  

 No argument with your analysis at all. I was merely trying to point out  that just because a battery starts the engine does NOT mean it has been "load  tested".

  

 If the engine will run with no electricity at all, who needs a battery? You  can prop it and go fly.

  

 Happy  Skies,



Old Bob

AKA

Bob Siegfried

Ancient Aviator

Stearman  N3977A

Brookeridge Air Park LL22

Downers Grove, IL 60516

630  985-8503



See what's free at AOL.com. 

  [quote][b]

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