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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Thu Aug 15, 2013 7:36 am Post subject: Failed brownout battery experiment

The backup battery died for my Dynon D-180.  My RV-12 is used for day VFR only.  A backup battery is not a necessity.  Instead of paying Dynon $130 every couple of years for a new backup battery, I thought of an alternative brownout circuit to prevent the D-180 from rebooting during engine start.  Not wanting to add the weight of a 7ah lead acid battery, I decided to use a couple of AA batteries.  I tapped into the load side of the start switch and connected to an AA battery holder, then to the External Backup Power input pin 15 on the back of the Dynon.  I figured that 3 volts from the AA batteries in series with the aricraft's 8 volts during engine start would provide the Dynon with 11 volts, one volt above the minimum required.  As you might have guessed, the experiment failed.  The Dynon still reboots during engine start.  Evidently the AA cells are unable to maintain their voltage and supply 1.5 amps for a couple of seconds during engine start.  Should I repeat the experiment using "D" cells?  Or is the whole idea flawed?

Comments and suggestions appreciated.

Joe

_________________
Joe Gores

ceengland7(at)gmail.com
Guest

Posted: Thu Aug 15, 2013 8:28 am Post subject: Failed brownout battery experiment

On 08/15/2013 10:36 AM, user9253 wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  --> AeroElectric-List message posted by: "user9253" <fransew(at)gmail.com> (fransew(at)gmail.com)



The backup battery died for my Dynon D-180.  My RV-12 is used for day VFR only.  A backup battery is not a necessity.  Instead of paying Dynon $130 every couple of years for a new backup battery, I thought of an alternative brownout circuit to prevent the D-180 from rebooting during engine start.  Not wanting to add the weight of a 7ah lead acid battery, I decided to use a couple of AA batteries.  I tapped into the load side of the start switch and connected to an AA battery holder, then to the External Backup Power input pin 15 on the back of the Dynon.  I figured that 3 volts from the AA batteries in series with the aricraft's 8 volts during engine start would provide the Dynon with 11 volts, one volt above the minimum required.  As you might have guessed, the experiment failed.  The Dynon still reboots during engine start.  Evidently the AA cells are unable to maintain their voltage and supply 1.5 amps for a couple of seconds during engine start.  Should I repeat the expe!

 

 riment using "D" cells?  Or is the whole idea flawed?

Comments and suggestions appreciated.

Joe



--------

Joe Gores

	
     	
     Short answer: that (series connection of the AA's) won't work.

     

     You could insert them in place of the original backup battery, but     the Dynon backup  is recharged constantly by the plane's supply     during normal operation.          

     http://www.dynonavionics.com/docs/D180_Feature_Battery.html     

     This means that the AA's will have charging voltage applied to them     constantly, & you'll likely have an acidic mess in the D-180     fairly quickly. 

     

     How about bringing the backup power terminals outside the unit,     & making up a Ni-MH battery pack with the same voltage/AH rating     as the Li-ion pack? It would be a bit larger & heavier, but     nothing like a lead-acid battery. And really inexpensive.

     

     Charlie

     [url=http://www.dynonavionics.com/docs/D180_Feature_Battery.html][/url]      [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 8:39 am Post subject: Failed brownout battery experiment

At 10:36 AM 8/15/2013, you wrote:

 	  Quote: 	
		  



The backup battery died for my Dynon D-180.  My RV-12 is used for 

day VFR only.  A backup battery is not a necessity.  Instead of 

paying Dynon $130 every couple of years for a new backup battery, I 

thought of an alternative brownout circuit to prevent the D-180 from 

rebooting during engine start.  Not wanting to add the weight of a 

7ah lead acid battery, I decided to use a couple of AA batteries.  I 

tapped into the load side of the start switch and connected to an AA 

battery holder, then to the External Backup Power input pin 15 on 

the back of the Dynon.  I figured that 3 volts from the AA batteries 

in series with the aricraft's 8 volts during engine start would 

provide the Dynon with 11 volts, one volt above the minimum 

required.  As you might have guessed, the experiment failed.  The 

Dynon still reboots during engine start.  Evidently the AA cells are 

unable to maintain their voltage and supply 1.5 amps for a couple of 

seconds during engine start.  Should I repeat the experiment using 

"D" cells?  Or is the whole idea flawed?

Comments and suggestions appreciated.

Joe


	


   The 'brown out' event is just a few hundred milliseconds

   long. Also, without the knowledge afforded by schematics

   and/or design goals for performance of the back-up battery

   power input pin, the precise cause for the failure is

   unknown.



   How low can the battery back up pin go and still support

   the dynon over the duration of a brown-out transient?



   Does the back up battery pin draw any current when the

   ship's power is OFF? In other words, what conditions

   must exist to relieve the back-up battery pin of any

   load?



   What is the load current demand on a back-up battery?



   You can explore these questions with an adjustable

   power supply hooked to the back-up battery pin.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 9:05 am Post subject: Failed brownout battery experiment

 	  Quote: 	
		  

   The 'brown out' event is just a few hundred milliseconds

   long.


	


    See http://tinyurl.com/pyszrmf

   Bob . . .

decaclops(at)gmail.com
Guest

Posted: Thu Aug 15, 2013 9:52 am Post subject: Failed brownout battery experiment

Or just pull the breaker, (if you have one), for the Dynon and close it 

after engine start. That's what I've been doing with a D-10 for years.



Ed Holyoke



On 8/15/2013 9:27 AM, Charlie England wrote:

 	  Quote: 	
		   On 08/15/2013 10:36 AM, user9253 wrote:

> 

>

> The backup battery died for my Dynon D-180.  My RV-12 is used for day VFR only.  A backup battery is not a necessity.  Instead of paying Dynon $130 every couple of years for a new backup battery, I thought of an alternative brownout circuit to prevent the D-180 from rebooting during engine start.  Not wanting to add the weight of a 7ah lead acid battery, I decided to use a couple of AA batteries.  I tapped into the load side of the start switch and connected to an AA battery holder, then to the External Backup Power input pin 15 on the back of the Dynon.  I figured that 3 volts from the AA batteries in series with the aricraft's 8 volts during engine start would provide the Dynon with 11 volts, one volt above the minimum required.  As you might have guessed, the experiment failed.  The Dynon still reboots during engine start.  Evidently the AA cells are unable to maintain their voltage and supply 1.5 amps for a couple of seconds during engine start.  Should I repeat the ex

 pe!
	


 	  Quote: 	
		  >

>   riment using "D" cells?  Or is the whole idea flawed?

> Comments and suggestions appreciated.

> Joe

>

> --------

> Joe Gores

 Short answer: that (series connection of the AA's) won't work.



 You could insert them in place of the original backup battery, but the

 Dynon backup  is recharged constantly by the plane's supply during

 normal operation.

 http://www.dynonavionics.com/docs/D180_Feature_Battery.html

 This means that the AA's will have charging voltage applied to them

 constantly, & you'll likely have an acidic mess in the D-180 fairly

 quickly.



 How about bringing the backup power terminals outside the unit, & making

 up a Ni-MH battery pack with the same voltage/AH rating as the Li-ion

 pack? It would be a bit larger & heavier, but nothing like a lead-acid

 battery. And really inexpensive.



 Charlie

 <http://www.dynonavionics.com/docs/D180_Feature_Battery.html>



 *

 *

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 10:00 am Post subject: Failed brownout battery experiment

 	  Quote: 	
		  Short answer: that (series connection of the AA's) won't work.



 You could insert them in place of the original backup battery, but the Dynon backup  is recharged constantly by the plane's supply during normal operation. 

  http://www.dynonavionics.com/docs/D180_Feature_Battery.html This means that the AA's will have charging voltage applied to them constantly, & you'll likely have an acidic mess in the D-180 fairly quickly. 



 How about bringing the backup power terminals outside the unit, & making up a Ni-MH battery pack with the same voltage/AH rating as the Li-ion pack? It would be a bit larger & heavier, but nothing like a lead-acid battery. And really inexpensive. 	


   Good input Charlie, 



   If it's a lithium battery that's being replaced,

   then an array of 4 lithium cells could be fabricated

   to put in place of the factory product. In fact,

   if one tears a Dynon battery apart, the picture

   on the website suggests that the cell pack is

   made form four of these guys . . .



  http://tinyurl.com/krgpjtx



   So it seems that for about $16 you could refurbish

   the original pack . . . 



   Referring to the D180_IM we read:



 [backup battery] Will operate the FlightDEK-D180 only if Master 

 Power is not present. The transition from Master 

 Power to External Backup Power will bring up a 

 warning, requiring you to press ACK within 30 

 seconds to keep the unit operating. This warning will 

 also display when transitioning from either Master or

 External Backup to Internal Battery power. 



    This sounds like a free floating input from an

    external power source that is not intended to be charged

    from within the D180 nor is it loaded unless

    main power is missing and limited to 30 seconds

    of loading unless acknowledged by pilot input.



    So an external battery on the order of 10-14

    volts will probably secure satisfactory brown-out

    performance. If a DIY refurb of internal battery

    using off the shelf, tabbed cells is not a option,

    then an external pak of cells tied to the

    bus through a series diode and perhaps a 200

    ohms (limit charging current to very low value)

    would take care of brown-out events. This external

    pack might be 4 lithium cells or maybe 8 Ni-Mh

    cells intended to be (1) used hundreds of milliseconds

    per flight and (2) very lightly charged from

    the bus.



 

   Bob . . .    [quote][b]

email(at)jaredyates.com
Guest

Posted: Thu Aug 15, 2013 10:40 am Post subject: Failed brownout battery experiment

ceengland7(at)gmail.com
Guest

Posted: Thu Aug 15, 2013 12:27 pm Post subject: Failed brownout battery experiment

On 08/15/2013 01:00 PM, Robert L.       Nuckolls, III wrote:

     

      	  Quote: 	
		          	  Quote: 	
		  Short answer: that         (series         connection of the AA's) won't work.

         

         You could insert them in place of the original backup battery,         but the         Dynon backup  is recharged constantly by the plane's supply         during         normal operation. 

                    http://www.dynonavionics.com/docs/D180_Feature_Battery.html         This means that the         AA's will         have charging voltage applied to them constantly, & you'll         likely         have an acidic mess in the D-180 fairly quickly. 

         

         How about bringing the backup power terminals outside the unit,         &         making up a Ni-MH battery pack with the same voltage/AH rating         as the         Li-ion pack? It would be a bit larger & heavier, but nothing         like a         lead-acid battery. And really inexpensive. 	
       

         Good input Charlie, 

       

         If it's a lithium battery that's being replaced,

         then an array of 4 lithium cells could be fabricated

         to put in place of the factory product. In fact,

         if one tears a Dynon battery apart, the picture

         on the website suggests that the cell pack is

         made form four of these guys . . .

       

                http://tinyurl.com/krgpjtx

       

         So it seems that for about $16 you could refurbish

         the original pack . . . 

       

         Referring to the D180_IM we read:

       

       [backup battery] Will operate the FlightDEK-D180 only if Master         

         Power is not present. The transition from Master 

         Power to External Backup Power will bring up a 

         warning, requiring you to press ACK within 30 

         seconds to keep the unit operating. This warning will 

         also display when transitioning from either Master or

         External Backup to Internal Battery power. 

         

          This sounds like a free floating input from an

          external power source that is not intended to be       charged

          from within the D180 nor is it loaded unless

          main power is missing and limited to 30 seconds

          of loading unless acknowledged by pilot input.

       

          So an external battery on the order of 10-14

          volts will probably secure satisfactory brown-out

          performance. If a DIY refurb of internal battery

          using off the shelf, tabbed cells is not a option,

          then an external pak of cells tied to the

          bus through a series diode and perhaps a 200

          ohms (limit charging current to very low value)

          would take care of brown-out events. This external

          pack might be 4 lithium cells or maybe 8 Ni-Mh

          cells intended to be (1) used hundreds of milliseconds

          per flight and (2) very lightly charged from

          the bus.

       

                

             Bob . . .       

     	
     From the same web page:

             

                 	  Quote: 	
		                The battery and         charging circuitry are conveniently encased within the EFIS         itself and automatically charge that battery anytime external         power is applied. 	
     

     Charlie

     

           [quote][b]

email(at)jaredyates.com
Guest

Posted: Thu Aug 15, 2013 12:36 pm Post subject: Failed brownout battery experiment

Well, maybe the little circuit does something else...  Charging was

just a logical guess on my part.



On Thu, Aug 15, 2013 at 4:25 PM, Charlie England <ceengland7(at)gmail.com> wrote:

 	  Quote: 	
		   On 08/15/2013 01:00 PM, Robert L. Nuckolls, III wrote:



 Short answer: that (series connection of the AA's) won't work.



 You could insert them in place of the original backup battery, but the Dynon

 backup  is recharged constantly by the plane's supply during normal

 operation.

 http://www.dynonavionics.com/docs/D180_Feature_Battery.html

 This means that the AA's will have charging voltage applied to them

 constantly, & you'll likely have an acidic mess in the D-180 fairly quickly.



 How about bringing the backup power terminals outside the unit, & making up

 a Ni-MH battery pack with the same voltage/AH rating as the Li-ion pack? It

 would be a bit larger & heavier, but nothing like a lead-acid battery. And

 really inexpensive.

   Good input Charlie,



   If it's a lithium battery that's being replaced,

   then an array of 4 lithium cells could be fabricated

   to put in place of the factory product. In fact,

   if one tears a Dynon battery apart, the picture

   on the website suggests that the cell pack is

   made form four of these guys . . .



 http://tinyurl.com/krgpjtx



   So it seems that for about $16 you could refurbish

   the original pack . . .



   Referring to the D180_IM we read:



 [backup battery] Will operate the FlightDEK-D180 only if Master

 Power is not present. The transition from Master

 Power to External Backup Power will bring up a

 warning, requiring you to press ACK within 30

 seconds to keep the unit operating. This warning will

 also display when transitioning from either Master or

 External Backup to Internal Battery power.



    This sounds like a free floating input from an

    external power source that is not intended to be charged

    from within the D180 nor is it loaded unless

    main power is missing and limited to 30 seconds

    of loading unless acknowledged by pilot input.



    So an external battery on the order of 10-14

    volts will probably secure satisfactory brown-out

    performance. If a DIY refurb of internal battery

    using off the shelf, tabbed cells is not a option,

    then an external pak of cells tied to the

    bus through a series diode and perhaps a 200

    ohms (limit charging current to very low value)

    would take care of brown-out events. This external

    pack might be 4 lithium cells or maybe 8 Ni-Mh

    cells intended to be (1) used hundreds of milliseconds

    per flight and (2) very lightly charged from

    the bus.



   Bob . . .

 From the same web page:



 The battery and charging circuitry are conveniently encased within the EFIS

 itself and automatically charge that battery anytime external power is

 applied.

 Charlie

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 3:10 pm Post subject: Failed brownout battery experiment

 	  Quote: 	
		   



  	  Quote: 	
		  The battery and charging circuitry are conveniently encased within the EFIS itself and automatically charge that battery anytime external power is applied. 	


 Charlie

 	


   The opening thought for this thread was to search out

   an alternative to the expensive, built-in battery.

   If it can be cloned from stock cells, then that

   would be the obvious  $low$ move.



   If not, then an external battery from li-ion or

   ni-mh with a trickle charge circuit would be a

   second choice.



   Doing the system integration to pin 15 was the

   unknown task . . .



 

 

   Bob . . .    [quote][b]

user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Thu Aug 15, 2013 5:28 pm Post subject: Re: Failed brownout battery experiment

The Dynon D-180 has 3 power inputs, the Master Power input on pin 1, External Backup Power on pin 15, and internal backup power using Dynon's proprietary Li-Ion $130 battery.   Pins 1 and 15 require between 10 and 30 volts.  The D-180 draws about 1.5 amps.  If voltage is available on pin 1, then the D-180 will not use power from pin 15.  No power is used from either input when the unit is turned off.  There is an alarm if power fails on pin 1.  But the alarm will silence automatically when power is restored on pin 1.  During engine start, the pilot never sees that alarm because it is only there for a millisecond.

  After the internal battery failed, I thought the same as Bob suggested: Buy 4 Li-Ion cells off eBay to replace the original ones.  It seemed like a simple and inexpensive solution until the new cells arrived in the mail and I tried replacing the old ones.  There is more to the battery pack than just batteries.  There is a circuit board about 1/2" x 2" that is glued to the batteries.  Evidently this circuit board monitors the voltage on each cell and charges each cell individually rather then treating all 4 cells as a single battery.  After all, these are Li-Ion cells that could cause a fire if not charged properly.  Normally I would never work on an electronic circuit with the power turned on.  But one can not turn off a battery.  Who knows if I damaged the circuit board by soldering live wires onto it in random sequence?  Another problem is that the battery compartment opening is just barely big enough to slide Dynon's battery pack in.  Just a few extra thousandths and the battery will not slide into the opening.  Of course my battery pack was too high to go in.  I took off some of the electrical tape and did manage to force it in.  But being worried about cells shorting out to the metal enclosure, I took my batteries out and abandoned the idea.  Why take a chance on a fire caused by my homemade Li-Ion battery pack?  Running the internal battery wires and plug outside of the case is not an option because the battery compartment door is on the side of the case and blocked by the D-180 mounting tray.

  As Charlie pointed out, the internal battery cable puts out a charging voltage.  I did not want to connect another type of battery to that.  So I decided to use pin 15, the External Battery input which does not receive a charging voltage from the D-180.  And it is accessible on the back of the case.

  I could just leave the D-180 turned off during engine start as Ed suggested.  But I like having it on to give the altimeter time to stabilize.  And monitoring electric fuel pump pressure is part of the pre-start checklist.

    I will continue to experiment and post my results.

Joe

_________________
Joe Gores

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 7:03 pm Post subject: Failed brownout battery experiment

At 08:28 PM 8/15/2013, you wrote:

 	  Quote: 	
		  



The Dynon D-180 has 3 power inputs, the Master Power input on pin 1, 

External Backup Power on pin 15, and internal backup power using 

Dynon's proprietary Li-Ion $130 battery.   Pins 1 and 15 require 

between 10 and 30 volts.  The D-180 draws about 1.5 amps.


	


    Okay, this means that 1 and 15 feed a switchmode power

    supply.  This will be a constant wattage input of 14w

    max according to the manual. So an 18-pack of AA alkaline

    cells as a backup battery would offer a backup supply of

    27 volts which would be loaded to the tune of 0.5A max

    for the few milliseconds of brownout.



    This figure is well within the capability of an AA

    alkaline. Given that the pak is loaded for hundreds

    of milliseconds once each flight, the battery pack

    service life should be measurable in years.



    Since it's only intended to provide brown-out

    mitigation, then you have no risk of latent failure

    going unnoticed before flight.



Evidently this circuit board monitors the voltage on each cell and 

charges each cell individually rather then treating all 4 cells as a 

single battery.



    Yup, just about everybody is doing smart batteries

    when populated with li-ion cells. Given that you

    never plan to run these things down, they'll only

    need to support the brown-out transient. So a

    series array trickle charged through a resistor

    is not even going to warm up. In fact, you'd

    probably want to use only 3 cells so that you can

    produce a nearly constant current through a resistor.



    Say the cranking transient draws 1.5A at 11 volts

    from a string of 3 cells for 500 milliseconds. That's

    about 7J of energy max. Okay, assume 80% charging

    efficiency so over the next hour, you'll want to

    stuff about 10J back into the cells. 10J at 10v

    for in 1 second is about 1 amp of recharge current.

    For one hour, it's 1/3600 or 277 microamps!



    I suspect these cells would not be seriously

    insulted with say, 1 milliamp of 100% duty

    cycle trickle charge, so a 5K resistor with

    a diode in series to prevent back feed would

    offer a top-off-trickle charge to the array.



    A similar approach could be considered for

    ni-mh array. Problem is the self-discharge

    rate of these cells would probably disqualify

    them. So a free standing AA alkaline pak or

    drip-charged li-ion pak seem the most viable

    battery options.



    How about an active option? A step up module

    like this one



http://tinyurl.com/m7t78eh



    could be set up to supply say 19 volts to

    pin 15 of the Dynon, but would certainly

    support 14 watts for 500 milliseconds during

    a brown-out.



    You might have some RFI issues with this

    necessitating some filters and perhaps

    a metallic enclosure . . . but it's

    small and the price is right.





   Bob . . .

klehman(at)albedo.net
Guest

Posted: Thu Aug 15, 2013 7:30 pm Post subject: Failed brownout battery experiment

FWIW I have a similar dc to dc converter in a plastic box running a 28v 

Turn & Bank instrument off 12 volts and have no RFI issues.

Ken



On 15/08/2013 10:58 PM, Robert L. Nuckolls, III wrote:

 	  Quote: 	
		   

 <nuckolls.bob(at)aeroelectric.com>



 At 08:28 PM 8/15/2013, you wrote:

> 

>

> The Dynon D-180 has 3 power inputs, the Master Power input on pin 1,

> External Backup Power on pin 15, and internal backup power using

> Dynon's proprietary Li-Ion $130 battery.   Pins 1 and 15 require

> between 10 and 30 volts.  The D-180 draws about 1.5 amps.



     Okay, this means that 1 and 15 feed a switchmode power

     supply.  This will be a constant wattage input of 14w

     max according to the manual. So an 18-pack of AA alkaline

     cells as a backup battery would offer a backup supply of

     27 volts which would be loaded to the tune of 0.5A max

     for the few milliseconds of brownout.



     This figure is well within the capability of an AA

     alkaline. Given that the pak is loaded for hundreds

     of milliseconds once each flight, the battery pack

     service life should be measurable in years.



     Since it's only intended to provide brown-out

     mitigation, then you have no risk of latent failure

     going unnoticed before flight.



 Evidently this circuit board monitors the voltage on each cell and

 charges each cell individually rather then treating all 4 cells as a

 single battery.



     Yup, just about everybody is doing smart batteries

     when populated with li-ion cells. Given that you

     never plan to run these things down, they'll only

     need to support the brown-out transient. So a

     series array trickle charged through a resistor

     is not even going to warm up. In fact, you'd

     probably want to use only 3 cells so that you can

     produce a nearly constant current through a resistor.



     Say the cranking transient draws 1.5A at 11 volts

     from a string of 3 cells for 500 milliseconds. That's

     about 7J of energy max. Okay, assume 80% charging

     efficiency so over the next hour, you'll want to

     stuff about 10J back into the cells. 10J at 10v

     for in 1 second is about 1 amp of recharge current.

     For one hour, it's 1/3600 or 277 microamps!



     I suspect these cells would not be seriously

     insulted with say, 1 milliamp of 100% duty

     cycle trickle charge, so a 5K resistor with

     a diode in series to prevent back feed would

     offer a top-off-trickle charge to the array.



     A similar approach could be considered for

     ni-mh array. Problem is the self-discharge

     rate of these cells would probably disqualify

     them. So a free standing AA alkaline pak or

     drip-charged li-ion pak seem the most viable

     battery options.



     How about an active option? A step up module

     like this one



 http://tinyurl.com/m7t78eh



     could be set up to supply say 19 volts to

     pin 15 of the Dynon, but would certainly

     support 14 watts for 500 milliseconds during

     a brown-out.



     You might have some RFI issues with this

     necessitating some filters and perhaps

     a metallic enclosure . . . but it's

     small and the price is right.





    Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Aug 15, 2013 7:57 pm Post subject: Failed brownout battery experiment

At 10:20 PM 8/15/2013, you wrote:

 	  Quote: 	
		  



FWIW I have a similar dc to dc converter in a plastic box running a 

28v Turn & Bank instrument off 12 volts and have no RFI issues.

Ken


	


    Good data . . . thank you.



   Bob . . .

uuccio(at)gmail.com
Guest

Posted: Fri Aug 16, 2013 12:40 pm Post subject: Failed brownout battery experiment

 	  Quote: 	
		   How about an active option? A step up module

   like this one

 

 http://tinyurl.com/m7t78eh

 

   could be set up to supply say 19 volts to

   pin 15 of the Dynon, but would certainly

   support 14 watts for 500 milliseconds during

   a brown-out.


	


Did you mean 14 *volts*?

How can you tell that it would support that for a half a second brownout?

user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Fri Aug 16, 2013 1:34 pm Post subject: Re: Failed brownout battery experiment

Today I tried using 2 "D" cells to boost the voltage during engine start.  But the Dynon D-180 still rebooted.

Next I tried 4 AA cells.  Success!

With the ignition off, I cranked the engine.  The D-180 did NOT reboot. 

Now if I could only find some CR14505 3 volt AA batteries to go into my 2 cell panel mounted battery holder.

I might take Bob's suggestion and use a DC to DC booster.

Schematic attached.

Joe

Brownout Batt.pdf

Description:

Download

Filename:

Brownout Batt.pdf

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_________________
Joe Gores

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Fri Aug 16, 2013 3:16 pm Post subject: Re: Failed brownout battery experiment

Any electronic device that fails during engine start is not well designed for the environment it is sold for. 



An old Car Talk line: Ask the manufacture to fix it. If they say 'they're all like that', just say 'fine; fix them all. Start with this one'.



Slumping voltage on power lines is easy to fix. Dynon certainly knows how to design the circuit. It's a good place to use a supercapacitor if the slump is low enough and long enough to warrant it, otherwise a capacitor will do.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

rickofudall

Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

Posted: Fri Aug 16, 2013 4:43 pm Post subject: Failed brownout battery experiment

Eric, Dang it! I was feeling like the kid at the back of the room who waves his arm valiantly even though he's not entirely sure he has an answer. Good to know I might have been learning something while I've been hanging out here. My question would have been, why not a capacitor to do the job rather than a battery? Would not a capacitor be able to take a charge from the system and then patiently wait to give it back when needed?

 Rick Girard

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On Fri, Aug 16, 2013 at 6:16 PM, Eric M. Jones <emjones(at)charter.net (emjones(at)charter.net)> wrote:

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		  --> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>

  

 Any electronic device that fails during engine start is not well designed for the environment it is sold for.

 

 An old Car Talk line: Ask the manufacture to fix it. If they say 'they're all like that', just say 'fine; fix them all. Start with this one'.

 

 Slumping voltage on power lines is easy to fix. Dynon certainly knows how to design the circuit. It's a good place to use a supercapacitor if the slump is low enough and long enough to warrant it, otherwise a capacitor will do.

  

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user9253

Joined: 28 Mar 2008
Posts: 1935
Location: Riley TWP Michigan

Posted: Fri Aug 16, 2013 5:10 pm Post subject: Re: Failed brownout battery experiment

I had thought about a capacitor.  It would have to be isolated with a diode or resistor or relay so that it does not give its energy to the starter motor.  And it would have to maintain at least 10 volts for 1/4 second.  What amount of capacitance is required?  Super capacitors are expensive.

Joe

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Joe Gores

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Joined: 24 Mar 2009
Posts: 95
Location: Medicine Lodge, KS

Posted: Fri Aug 16, 2013 6:23 pm Post subject: Re: Failed brownout battery experiment

Okay, it's pretty easy to run the numbers from the perspective of the transfer of energy from a capacitor to some load. The energy stored on a capacitor is (C*E^2)/2 = Joules. We deduced a need for 7 Joules to be available to the D180 at 10V or greater.



The charging source is the battery. A fully charged battery would rest at about 13.0 volts. So energy stored at 13 volts minus remaining energy at 10 volts must be 7Joules or more. 



(C*13^2)/2 - (C*10^2)/2 = 7



169C/2 - 100C/2 = 7



69C/2 = 7



34.5C = 7



C = 7/34.5 = 0.2 Farads



The capacitor should be good for at least 15 volts unless you're going to disconnect it with the alternator running. As you've noted, it would also need to be diode or switch isolated from the bus to prevent back-feed. A diode would offer significant impact to the e-squared nature of energy stored . . . so perhaps relay or switch contacts should be used to unhook the capacitor from the bus milliseconds before starter is engaged.



AA cells are not well suited to 1+ amp discharge situations but as you've discovered, D-cells took the hit nicely. A d-cell array is certainly cost attractive but gives you another battery to maintain. But it gets pre-flight tested every start-up. I suspect service life on a d-cell array would be quite long.  A super-cap is maintenance free but not cheap and pretty hefty in size.  The DC to DC converter is small, maintenance free and the price is certainly right.



It appears you have a constellation of options to consider.

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