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Z-13 Ammeter Relocation Question

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jmjones2000(at)mindspring
Guest

Posted: Fri Mar 13, 2015 4:55 pm Post subject: Z-13 Ammeter Relocation Question

How would I elegantly wire a single shunt to the Z-13 diagram to show me the electrons flowing into and out of the battery?



Z-13 shows ammeters on each alternator B-lead.  This will indicate the amount of electrons leaving the alternator and going into either the aircraft load, the battery, or both.  I am more interested in the amount of electrons coming into and going out of the battery.  I have and electrically dependent engine, and the standby alternator is a 20 amp B&C gear driven alternator (BC-410H).



As suggested by Bob in an earlier post, I have done a load analysis and know the position of the cockpit switches in the event of a primary alternator/regulator failure, and also the switch positions if the secondary alternator/regulator fails. 



There is a low voltage warning system installed that will show me when an alternator fails by flashing a light.  



Correct me if I am wrong, but with an ammeter in a position to monitor the electrons coming and going to the battery, it can be used as a tool to monitor the health of the battery. 



The way I understand it the alternator is intended to carry the entire running load of the electrical system. If the current draw is greater than the alternator output (for any reason), it would show a discharge on the battery.  I have a Dynon electric engine monitor and have the ability to fine tune where the “red” or ‘yellow” arcs are at.  It would be easy to show a warning if the amps began indicating less than zero (indicating a discharging battery). 



It would seem beneficial to be able to watch the battery take the charge after start, and to taper off with time, indicating the health of the battery.



I would like to hear some other opinions on why locating a shunt on each alternator is a better idea. 



I would also like to see the best option for hooking up a single shunt to the battery if I decide to go that way.



Thanks for the help!

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user9253

Joined: 28 Mar 2008
Posts: 1921
Location: Riley TWP Michigan

Posted: Sat Mar 14, 2015 5:43 am Post subject: Re: Z-13 Ammeter Relocation Question

The Dynon Skyview installation guide shows 3 possible locations for an ammeter shunt.  See page 7-52.

http://tinyurl.com/Dynon-Install-Guide

I never thought that a battery ammeter was very useful until reading about this accident.

http://forums.matronics.com/viewtopic.php?t=16757524

A battery ammeter might have helped the pilot realize why the aircraft system voltage was dropping so fast.  He then could have opened the battery contactor before the engine quit.

Joe

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_________________
Joe Gores

jmjones2000(at)mindspring
Guest

Posted: Sat Mar 14, 2015 10:54 am Post subject: Z-13 Ammeter Relocation Question

For $62, a 500A shunt and digital ammeter can be purchased. In the unlikely event of a shorted battery, the shunt would act like a 500A current limiter and remove the battery from the system. This is assuming the shunt is hooked up directly to and at the battery.  



 	  Quote: 	
		   On Mar 14, 2015, at 05:43, user9253 <fransew(at)gmail.com> wrote:

 

 

 

 The Dynon Skyview installation guide shows 3 possible locations for an ammeter shunt.  See page 7-52.

 http://tinyurl.com/Dynon-Install-Guide

 I never thought that a battery ammeter was very useful until reading about this accident.

 http://forums.matronics.com/viewtopic.php?t=16757524

 A battery ammeter might have helped the pilot realize why the aircraft system voltage was dropping so fast.  He then could have opened the battery contactor before the engine quit.

 Joe

 

 --------

 Joe Gores

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=439356#439356

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nuckolls.bob(at)aeroelect
Guest

Posted: Sat Mar 14, 2015 4:18 pm Post subject: Z-13 Ammeter Relocation Question

The single most important instrumentation

   in the airplane's electrical system is active

   notification of low voltage. The bus cannot rise

   above 13.0 volts without aid of a functioning

   alternator.



   If the battery is being sized and maintained to

   accomplish battery-only endurance operations with

   certainty, then its capacity is a known quantity.

   Once the capacity falls below this design goal,

   prudent operations call for replacing it.



   This happens when the battery has lost about 20%

   of its as-installed capacity. This value will be

   reached before it begins to show signs of weakness

   by either (1) lethargic engine cranking or (2)

   rapid decay of the recharge current after the

   alternator starts.



   If the airplane is not electrically dependent

   and no battery-only endurance goals are in place,

   then your best indicator of battery condition

   will be cranking performance. If it got the engine

   started, you're good to fly.



   In the well crafted electrical system, ammeters

   yield no useful flight-ops information. When the

   alternator is running, all loads are, or should

   be, known. Hence as long as the low volts lite

   is out, all is right with the universe.



   If the alternator quits, all endurance loads are

   known as well as the battery's ability to grunt

   said loads to design goals. Again, ammeters are

   cool gages with wiggly pointers . . . but not

   useful for flight-ops guidance (or clues as to

   battery condition).



   Now, if you truly want a -0+ battery ammeter,

   you'll need to arrange for the shunt NOT to carry

   starter current so that the ammeter sees only

   flow to/from the battery. This still doesn't measure

   loads in the endurance mode but it will let you

   interpret recharge behavior after a start.

   

   Like so . . .



 [img]cid:.0[/img]



  

 

   Bob . . .

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