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Charging System Theory - A few Questions

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darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat May 16, 2009 4:27 pm Post subject: Charging System Theory - A few Questions

Ok, I have a couple questions for people that are smarter than myself when it comes to electronics.  These questions have to do with the charging system and how it works.



I've got a 914 and had a dual alternator setup on it for awhile...this worked flawlessly until my external alternator crapped out on me.  I had it rebuilt but have not put it back on yet for many reasons, one being that it runs on the vacuum pump gear which only turns .52:1 to the engine so it doesn't really come alive until 3000 to 3500 rpm.  This is not a problem by itself but I tend to think that this type of loading may have lead to its early demise...probably not but maybe.  Anyway, I think the built-in generator provides just enough power for my needs anyway but have a few questions on this setup.  Here they are:



1. I flew for two hours this morning and the whole time my system voltage showed 14.0V on my EIS.  Now I have an ammeter on the positive lead of the battery showing amp draw in (+) or out (-) of battery.  This varied consistently through the two hour flight between +5 and -5 with most of the time around +2.  The battery is kept on a tender so it was completely charged when the flight started.  I was told by a guy at the airport that a battery will only take the amps it needs as it needs them so a discharged, or low charged battery would take and show more amps going in than a fully charged battery.  Is this how it works?  



2.  I also was wondering about the regulator/rectifier.  Does this regulate the amount of power going to the battery?  In other words, does it sense battery voltage and send current as needed to the battery to maintain the charge or is it always charging regardless of system or battery voltage?



After the flight, I checked my battery with my multi-meter and it show 13.0V so it was still fully charged after two hours of flying so the system is obviously working (again the EIS aslo showed 14.0V the entire flight), I am simply curious as to how it works.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

kerrjohna(at)comcast.net
Guest

Posted: Sat May 16, 2009 5:55 pm Post subject: Charging System Theory - A few Questions

Darin, did you fly to Logan? Â A Kitfox landed and departed while I had the Hatz up. Â After about 45 minutes over the airport the engine quit. Â Will update for the interested when the cause is determined.



My understanding is that the voltage regulator does just that, regulates the voltage out of the alternator/generator to no more than 13.8 (Theoretically). Â The generating beast puts out voltage more or less linearly according to rpm. Â You saw this with your gear drive alternator. Â My understanding is as suggested that the battery draws the amps needs to become charged. Â Can't understand why you would have negative amps unless the equipment draw changed and exceeded the capacity of the alternator.

John

---

KITFOXZ(at)aol.com
Guest

Posted: Sat May 16, 2009 6:36 pm Post subject: Charging System Theory - A few Questions

Hello Darin,

  

 I'll take a crack at your questions.  Although I am not a degreed  electronics engineer, I have worked my whole life as an electronics tech.   I earned my education in electronics through the United States Navy  Avionics B School.  This is a course of study comparable to many university  electronics engineering programs of the time.

  

 First, your aircraft does not have a true "charging system".  It  simply has a battery and an alternator/regulator that are in parallel with each  other.  They are both sources of DC power.  The alternator and it's  rectifier/regulator work as a system that produce a regulated output voltage of  13.8 - 14 VDC.  The Rotax built-in alternator has a very limited current  output capability and so that regulated output of 13.8 - 14 VDC may fall below  it's regulated voltage point if the ship's load is great enough.

  

 One of the battery's purposes is to help stabilize the alternator's output  during these peak load times.  That is why you see the ammeter show a  negative value at times.  --The alternator is not keeping up with the power  demands of the ship's power bus and so the battery is supplying the deficit  power.  It is suffering a net discharge.

  

 When the battery's voltage drops below the output voltage of the  alternator's, --the battery is taking on a charge.  It charges back up to  the applied voltage of 13.8 - 14 VDC  This is true unless the ship's power  buss is using more power than the alternator can produce.

  

 The fact that you see an average of +2 amps on your ammeter demonstrates  that on average you are producing enough power to the buss to supply all  system's needs and keep the battery charged.  If you turned on your landing  lights, electric deicing boots, electric seat heater and your radar jamming  countermeasures transmitters, your average ammeter reading would be deep in the  negative and your battery would soon be dead.

  

 The guy at your airport is essentially right in that the battery's  fully charged voltage is about 14 volts.  It will not charge any higher  than that because the regulator's output is limited to that value.  If the  regulator were to output a higher voltage, the fully charged battery would heat  and boil more electrolyte out and soon would go dry without attention.  The  chemistry of the battery will not allow it to raise it's voltage too much  higher.   

  

 You may think of the battery and alternator as being in equilibrium most of  the time.  The battery's voltage is pushing back at the alternator's output  and they are equal.  When the battery's voltage is below this point,  some alternator current flows to it to charge it back up.

  

 You can succeed in your arrangement as long as you know when your load is  exceeding your alternator's output and take action to reduce power consumption  as needed.  As long as you average in the positive range of your ammeter  reading you should be good.

  

 I don't think the gear ratio of your external alternator to shaft speed had  anything to do with it's failure.  I would be curious to know what the  specific failure was though.

  

 I hope this is helpful to you.  There are others on the list who may  be able to offer more.

  

 John P. Marzluf

 Columbus, Ohio

 Outback (out back in the garage)     

  

  In a message dated 5/16/2009 8:29:05 P.M. Eastern Daylight Time,  gerns25(at)netscape.net writes:

  	  Quote: 	
		  -->    Kitfox-List message posted by: "darinh"    <gerns25(at)netscape.net>



Ok, I have a couple questions for people    that are smarter than myself when it comes to electronics.  These    questions have to do with the charging system and how it works.



I've    got a 914 and had a dual alternator setup on it for awhile...this worked    flawlessly until my external alternator crapped out on me.  I had it    rebuilt but have not put it back on yet for many reasons, one being that it    runs on the vacuum pump gear which only turns .52:1 to the engine so it    doesn't really come alive until 3000 to 3500 rpm.  This is not a problem    by itself but I tend to think that this type of loading may have lead to its    early demise...probably not but maybe.  Anyway, I think the built-in    generator provides just enough power for my needs anyway but have a few    questions on this setup. Here they are:



1. I flew for two hours this    morning and the whole time my system voltage showed 14.0V on my EIS.  Now    I have an ammeter on the positive lead of the battery showing amp draw in (+)    or out (-) of battery.  This varied consistently through the two hour    flight between +5 and -5 with most of the time around +2.  The battery is    kept on a tender so it was completely charged when the flight started.  I    was told by a guy at the airport that a battery will only take the amps it    needs as it needs them so a discharged, or low charged battery would take and    show more amps going in than a fully charged battery.  Is this how it    works?  



2.  I also was wondering about the    regulator/rectifier.  Does this regulate the amount of power going to the    battery?  In other words, does it sense battery voltage and send current    as needed to the battery to maintain the charge or is it always charging    regardless of system or battery voltage?



After the flight, I checked my    battery with my multi-meter and it show 13.0V so it was still fully charged    after two hours of flying so the system is obviously working (again the EIS    aslo showed 14.0V the entire flight), I am simply curious as to how it    works.



--------

Darin Hawkes

Series 7 

914 Turbo

Kaysville,    Utah





Read this topic online    here:



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Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat May 16, 2009 7:14 pm Post subject: Charging System Theory - A few Questions

1.  That's pretty  much it...  A discharged battery will absorb current from

the generator.  The purpose of the regulator is to keep the voltage high

enough so the pattery can absorb power... this is generally at 13.8V.  BTW I

don't personally recommend putting the battery on a tender and leaving it

for extended periods of time.  If you want to do that look into a pulse

charger.  Even a small continuous current can boil a battery in time.



2.  The regulator rectifier does two jobs.  It converts AC current produced

by the alternator to DC current which your radios, etc use.  It also keeps

the output of the alternator at around 13.8V  As a discharged battery starts

to charge it will drop the voltage slightly causing the regulator to allow

the alternator to produce more current to keep the whole system at around

13.8V  The further discharged your battery is the higher the ammeter + will

read.  The voltage should remain more or less consist ant...  That is the

job of the regulator.



Note there is a margin of usability on the voltage.  14.0 V is ok (at) 15V I'd

land and check out things.



Noel



--

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat May 16, 2009 7:21 pm Post subject: Charging System Theory - A few Questions

John:  

   

That is exactly when the ammeter will go negative  

   

Certified aircraft in Canada are only allowed to install loads to 80% or the capacity of the alternator if they do not have a load meter.Â  If they do have a load meter they are allowed to install no more than 100% of the generating capacity of their engine.  

   

Homebuilt or amateur built aircraft can do as they please but for me the 80% Â rule is good common horse sense...   

   

Noel  

       

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of kerrjohna(at)comcast.net

 Sent: 16 May 2009 11:21 PM

 To: kitfox-list(at)matronics.com

 Subject: Re: Charging System Theory - A few Questions  

  

  

     

Darin, did you fly to Logan?  A Kitfox landed and departed while I had the Hatz up.  After about 45 minutes over the airport the engine quit.  Will update for the interested when the cause is determined.    

   

    

My understanding is that the voltage regulator does just that, regulates the voltage out of the alternator/generator to no more than 13.8 (Theoretically).  The generating beast puts out voltage more or less linearly according to rpm.  You saw this with your gear drive alternator.  My understanding is as suggested that the battery draws the amps needs to become charged.  Can't understand why you would have negative amps unless the equipment draw changed and exceeded the capacity of the alternator.  

    

   

    

John

 ---

_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

Float Flyr

Joined: 19 Jul 2006
Posts: 2704
Location: Campbellton, Newfoundland

Posted: Sat May 16, 2009 7:26 pm Post subject: Charging System Theory - A few Questions

A very nice description... Much better than my hack at it!  I take it military aircraft are allowed to have more equipment thant 100% of generating capacity on board.  

   

noel  

       

From: owner-kitfox-list-server(at)matronics.com [mailto:owner-kitfox-list-server(at)matronics.com] On Behalf Of KITFOXZ(at)aol.com

 Sent: 17 May 2009 12:01 AM

 To: kitfox-list(at)matronics.com

 Subject: Re: Charging System Theory - A few Questions  

  

  

     

Hello Darin,  

    

   

    

I'll take a crack at your questions.  Although I am not a degreed electronics engineer, I have worked my whole life as an electronics tech.  I earned my education in electronics through the United States Navy Avionics B School.  This is a course of study comparable to many university electronics engineering programs of the time.  

    

   

    

First, your aircraft does not have a true "charging system".  It simply has a battery and an alternator/regulator that are in parallel with each other.  They are both sources of DC power.  The alternator and it's rectifier/regulator work as a system that produce a regulated output voltage of 13.8 - 14 VDC.  The Rotax built-in alternator has a very limited current output capability and so that regulated output of 13.8 - 14 VDC may fall below it's regulated voltage point if the ship's load is great enough.  

    

   

    

One of the battery's purposes is to help stabilize the alternator's output during these peak load times.  That is why you see the ammeter show a negative value at times.  --The alternator is not keeping up with the power demands of the ship's power bus and so the battery is supplying the deficit power.  It is suffering a net discharge.  

    

   

    

When the battery's voltage drops below the output voltage of the alternator's, --the battery is taking on a charge.  It charges back up to the applied voltage of 13.8 - 14 VDC  This is true unless the ship's power buss is using more power than the alternator can produce.  

    

   

    

The fact that you see an average of +2 amps on your ammeter demonstrates that on average you are producing enough power to the buss to supply all system's needs and keep the battery charged.  If you turned on your landing lights, electric deicing boots, electric seat heater and your radar jamming countermeasures transmitters, your average ammeter reading would be deep in the negative and your battery would soon be dead.  

    

   

    

The guy at your airport is essentially right in that the battery's fully charged voltage is about 14 volts.  It will not charge any higher than that because the regulator's output is limited to that value.  If the regulator were to output a higher voltage, the fully charged battery would heat and boil more electrolyte out and soon would go dry without attention.  The chemistry of the battery will not allow it to raise it's voltage too much higher.     

    

   

    

You may think of the battery and alternator as being in equilibrium most of the time.  The battery's voltage is pushing back at the alternator's output and they are equal.  When the battery's voltage is below this point, some alternator current flows to it to charge it back up.  

    

   

    

You can succeed in your arrangement as long as you know when your load is exceeding your alternator's output and take action to reduce power consumption as needed.  As long as you average in the positive range of your ammeter reading you should be good.  

    

   

    

I don't think the gear ratio of your external alternator to shaft speed had anything to do with it's failure.  I would be curious to know what the specific failure was though.  

    

   

    

I hope this is helpful to you.  There are others on the list who may be able to offer more.  

    

   

    

John P. Marzluf  

    

Columbus, Ohio  

    

Outback (out back in the garage)       

    

   

      

In a message dated 5/16/2009 8:29:05 P.M. Eastern Daylight Time, gerns25(at)netscape.net writes:  

   	  Quote: 	
		    

--> Kitfox-List message posted by: "darinh" <gerns25(at)netscape.net>

 

 Ok, I have a couple questions for people that are smarter than myself when it comes to electronics.  These questions have to do with the charging system and how it works.

 

 I've got a 914 and had a dual alternator setup on it for awhile...this worked flawlessly until my external alternator crapped out on me.  I had it rebuilt but have not put it back on yet for many reasons, one being that it runs on the vacuum pump gear which only turns .52:1 to the engine so it doesn't really come alive until 3000 to 3500 rpm.  This is not a problem by itself but I tend to think that this type of loading may have lead to its early demise...probably not but maybe.  Anyway, I think the built-in generator provides just enough power for my needs anyway but have a few questions on this setup. Here they are:

 

 1. I flew for two hours this morning and the whole time my system voltage showed 14.0V on my EIS.  Now I have an ammeter on the positive lead of the battery showing amp draw in (+) or out (-) of battery.  This varied consistently through the two hour flight between +5 and -5 with most of the time around +2.  The battery is kept on a tender so it was completely charged when the flight started.  I was told by a guy at the airport that a battery will only take the amps it needs as it needs them so a discharged, or low charged battery would take and show more amps going in than a fully charged battery.  Is this how it works?  

 

 2.  I also was wondering about the regulator/rectifier.  Does this regulate the amount of power going to the battery?  In other words, does it sense battery voltage and send current as needed to the battery to maintain the charge or is it always charging regardless of system or battery voltage?

 

 After the flight, I checked my battery with my multi-meter and it show 13.0V so it was still fully charged after two hours of flying so the system is obviously working (again the EIS aslo showed 14.0V the entire flight), I am simply curious as to how it works.

 

 --------

 Darin Hawkes

 Series 7 

 914 Turbo

 Kaysville, Utah

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=244303#244303======================

 =======================              - MATRONICS WEB FORUMS =======================            - List Contribution Web Site sp;                         =

 

 

   	
  

    

       

  

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_________________
Noel Loveys
Kitfox III-A
Aerocet 1100 Floats

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat May 16, 2009 8:17 pm Post subject: Re: Charging System Theory - A few Questions

 	  kerrjohna(at)comcast.net wrote: 	
		  Darin, did you fly to Logan?  A Kitfox landed and departed while I had the Hatz up.--- 	




Yes John that was me.  I saw you with your Hatz out and thought that was you orbiting the airport.  I heard you make the call and stayed on the radio until I heard you announce "high final...dead stick"  and thought at least you had made it to the runway.  Sounds like it was a successful deadstick landing though and that is good.  I for one would be interested in hearing the cause when you find it.  By the way, that is a beautiful biplane!  Nice job.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sat May 16, 2009 9:14 pm Post subject: Re: Charging System Theory - A few Questions

 	  KITFOXZ(at)aol.com wrote: 	
		  Hello Darin,

  

 I'll take a crack at your questions.  Although I am not a degreed  electronics engineer, I have worked my whole life as an electronics tech.ï¿½  I earned my education in electronics through the United States Navy  Avionics B School.  This is a course of study comparable to many university  electronics engineering programs of the time.

  

 First, your aircraft does not have a true "charging system".  It  simply has a battery and an alternator/regulator that are in parallel with each  other.  They are both sources of DC power.  The alternator and it's  rectifier/regulator work as a system that produce a regulated output voltage of  13.8 - 14 VDC.  The Rotax built-in alternator has a very limited current  output capability and so that regulated output of 13.8 - 14 VDC may fall below  it's regulated voltage point if the ship's load is great enough.

  

 One of the battery's purposes is to help stabilize the alternator's output  during these peak load times.  That is why you see the ammeter show a  negative value at times.  --The alternator is not keeping up with the power  demands of the ship's power bus and so the battery is supplying the deficit  power.  It is suffering a net discharge.....



 John P. Marzluf

 Columbus, Ohio

 Outback (out back in the garage)     

  

  	




John,



Thanks for that reply...answered all my questions and them some!  That all makes sense and is basically how I understood the system but was not sure.  The fact is that I would like to be able to run my lighting, strobes and navs along with a few other things like my deicing boots and radar jamming counter measures transmitters (actually just my heater fans) so I need to get my other alternator back on and see why it is causing my oil temp gauge to fluctuate wildly.  Which brings up another question (I'll make it blue text to stand out):



Do I need another noise suppression capacitor on bolt on alternator?  it is the same (or very similar) to the Rotax add-on altenator but it runs on the vacuum pump pad.  It is internally regulated and rectified but does not have any internal noise suppression.  I noticed that the wiring diagram in my engine installation manual shows the add-on alternator requiring a capacitor also.  I ask because someone told me I didn't need one on both onboard and add-on alternators but it is there in the manual.  I ordered one from John and have it so I am going to put it on unless someone can tell me why I don't need it.  I get quite a bit of noise from it when I transmit...to the point that the tower has a hard time understanding.  This doesn't happen when running on the Rotax generator that is on a capacitor.



By the way, the alternator coil leads broke.  The shop that rebuilt it said the original leads were very small and brittle and a couple other broke just in the disassembly.  Apparently, the place that supplied the alternator did quite a bit of custom machining (custom shaft with spline gear, mount and stock mounting bracket removal) but the attachment of the coil leads was pretty crappy.  They are now done with larger copper and ring terminals on each lead.  It is a Nippondenso 60A alternator if you are curious but turned down like it is it only produce 30A - 40A....plenty for my bird.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

KITFOXZ(at)aol.com
Guest

Posted: Sun May 17, 2009 4:51 am Post subject: Charging System Theory - A few Questions

Darin,

  

 Another Capacitor?  OK, this will take a few more paragraphs to  answer.  The short answer is that yes, it will help.  All alternators  produce voltage that is full of peaks and valley's.  Batteries produce  smooth DC power.  This is problematic for sensitive avionics equipment  because they run best on pure Swiss chocolate smooth DC.  The alternator's  regulator minimizes these peaks and valleys but, still they are there.

  

 A large value (22,000 microfarad) filter capacitor will do a bunch of  smoothing of that pulsing, peaking, jerking short duration valley,  voltage being supplied by your alternators.  If pure DC voltage is  depicted by a smooth straight line across the page, a long line of cursive lower  case m's and i's across the page is what the output voltage will look like  unfiltered.  This alternator "noise" is a part of what you hear in your  radio audio.  A filter capacitor located as close to the alternator  regulator's output as is practical is best to minimize it.  

  

 The water bucket analogy:

  

 Consider a bucket of water.  The bucket is full of water and there is  a small hole in the side of it near the bottom.  A stream of water is  coming out of the hole propelled by the weight of the full bucket of water (head  pressure) and it is projecting out several inches to the side before gravity has  it's way with the stream and forces it to the ground.  Let's just say for  fun that the stream hitting the ground is doing so at thirty-six inches from the  bucket horizontally.  This must be a big (deep) bucket I am talking  about!

  

 As long as the bucket is kept full, the stream is a full 36 inches  strong.  Let the bucket get partially empty and the stream is hurting for  distance.  (Insert prostate jokes here) 

  

 Instead of water, your filter capacitor stores electrical current.   Keep the capacitor full of electrons and the ship's buss will not feel much  effect from any of those valleys (low bucket water) --when the alternator is  outputting a valley.   Add a peak or pulse of higher voltage to the  capacitor's stores and the buss only detects a minimal increase in "water  pressure".  The capacitor is a pretty good passive voltage filter  mechanism. 

  

 THE MOST IMPORTANT REQUIREMENT OF ALL ELECTRONICS (AVIONICS) EQUIPMENT IS  TO HAVE THE LUXURY OF SOLID, SMOOTH AND AMPLE DC POWER! 

  

 --Mess with that and you get what you get, --noisy radio receivers,  unintelligible radio transmissions, GPS receivers that crash and reboot, RADAR  jamming electronic countermeasures transmitters that tell the enemy it's  just you and your noisy sh*t overhead again!    

  

 The ship's battery plays a big role in keeping the buss smooth like Swiss  chocolate.  The battery is actually a better filter than the capacitor but  it is located some distance from the alternator and this hurts.  If noise  is not suppressed as soon as practical and hopefully right at the source, the  ship's buss will still be affected.

  

 Shut the engine down and you have the ideal environment, no alternator  noise, no ignition impulse noise, and no electrostatic noise from all engine  vibration related mechanical parts clanging together.

  

 We all should sell our Foxes and go sailplaning!

  

 John

  

 John P. Marzluf

 Columbus, Ohio

 Outback (out back in the garage)

  

    

  

  In a message dated 5/17/2009 1:16:12 A.M. Eastern Daylight Time,  gerns25(at)netscape.net writes:

  	  Quote: 	
		  John,



Thanks for that reply...answered all my questions and them    some!  That all makes sense and is basically how I understood the system    but was not sure.  The fact is that I would like to be able to run my    lighting, strobes and navs along with a few other things like my deicing boots    and radar jamming counter measures transmitters (actually just my heater fans)    so I need to get my other alternator back on and see why it is causing my oil    temp gauge to fluctuate wildly.  Which brings up another question (I'll    make it blue text to stand out):



Do I need another noise suppression    capacitor on bolt on alternator?  it is the same (or very similar) to the    Rotax add-on altenator but it runs on the vacuum pump pad.  It is    internally regulated and rectified but does not have any internal noise    suppression.  I noticed that the wiring diagram in my engine installation    manual shows the add-on alternator requiring a capacitor also.  I ask    because someone told me I didn't need one on both onboard and add-on    alternators but it is there in the manual.  I ordered one from John and    have it so I am going to put it on unless someone can tell me why I don't need    it.  I get quite a bit of noise from it when I transmit...to the point    that the tower has a hard time understanding.  This doesn't happen when    running on the Rotax generator that is on a capacitor.



By the way, the    alternator coil leads broke.  The shop that rebuilt it said the original    leads were very small and brittle and a couple other broke just in the    disassembly.  Apparently, the place that supplied the alternator did    quite a bit of custom machining (custom shaft with spline gear, mount and    stock mounting bracket removal) but the attachment of the coil leads was    pretty crappy.  They are now done with larger copper and ring terminals    on each lead.  It is a Nippondenso 60A alternator if you are curious but    turned down like it is it only produce 30A - 40A....plenty for my    bird.



--------

Darin Hawkes

Series 7 

914 Turbo

Kaysville,    Utah

	


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  [quote][b]

occom

Joined: 26 Aug 2006
Posts: 404

Posted: Sun May 17, 2009 7:23 am Post subject: Charging System Theory - A few Questions

Nobody has adresses HOW the regulator rectifier works so I'll toss in that 

bit.



Most of the alternators I've seen on the Rotax's are permanant magnet type, 

meaning they have a magnet as the rotor in their center. When the magnet is 

rotated, it's magnetic field causes electricity to be excited in the coils 

surrounding it. In an open circuit this voltage can be quite high, 40V is 

common. This electricity is alternating current. and must be changed into 

direct current before we can use it. this is done externally on the stock 

alternator using a recitifier bridge (a set of diodes). What you have now is 

DC as far as it matters for us, but this type of alternator with the 

permanant magnet cannot adjust it's output to match demand. It will put out 

all it can, all the time and the faster it spins the more power it puts out 

so we have to put a gate (regulator) of some type on the output to keep the 

rush of electrons from frying all the stuff that gets hooked up to it. 

There's two ways to go with regulators as we use them here. In most of them 

we open a gate to send the excess power directly to ground whenever votage 

exceeds a determined point, this is a shunt regulator and the type Rotax 

supplies. The alternative is to hold back the invading hordes by slamming 

the gate shut, opening the circuit. The second one is called a series 

regulator. There are advantages and disadvantages to each. The Key West 

regulator is a series type I believe, while all the tympanium types supplied 

by Rotax are shunt regulators. Noise suppression, important to anyone with a 

radio is supposed to be easier with shunt regulators.



The important thing here is that with a shunt regulator, the generating coil 

is putting out basically all the power it is capable of, all the time. If 

this power has to be shunted to ground, as it would if you had very low 

loads, the regulator will get warmer than if you are using all the power 

elsewhere. So if your system is properly sized and you are not actually 

depleting the battery during a normal flight then adding generating capacity 

will be a way to make your system noisier and less happy (just the opposite 

of what you would guess).



The last way of doing it, and the best (IMO) is the excited field 

alternator. In this one, the permanent magnet is replaced buy an 

electromagnet, thus there is nothing generated until power is supplied to 

energize the magnet. In these ones the regulator supplied the magnet coil 

only enough power to make the output exactly match demand. Cool, quiet, and 

efficient it is somewhat more expensive and complex. In any case it's not 

used on Rotax, Jabiru, Hirth, or many others. It is used on your car though.



Although I believe this to be accurate and reliable information, as with 

anything you read on the internet use common sense.

Do not archive,

patreilly43(at)hotmail.co
Guest

Posted: Sun May 17, 2009 7:23 am Post subject: Charging System Theory - A few Questions

John C Thank you for the electrical explainations. Make sure you chime in as early as possible on electrical topics. Most electrical engineer degreed people don't explain as simply and concise as you. Experience outweighs formal education every time. As Mark Twain said C "Don't let too much schooling get in the way of getting a good education".

 do not archive 

 Pat Reilly

 Mod 3 582 Rebuild

 Rockford C IL 

 	  Quote: 	
		   Subject: Re: Charging System Theory - A few Questions

 From: gerns25(at)netscape.net

 Date: Sat C 16 May 2009 22:14:28 -0700

 To: kitfox-list(at)matronics.com

 --> Kitfox-List message posted by: "darinh" <gerns25(at)netscape.net>

 KITFOXZ(at)aol.com wrote:

 > Hello Darin C

 > 

 > I'll take a crack at your questions. Although I am not a degreed electronics engineer C I have worked my whole life as an electronics tech.ï¿½ I earned my education in electronics through the United States Navy Avionics B School. This is a course of study comparable to many university electronics engineering programs of the time.

 > 

 > First C your aircraft does not have a true "charging system". It simply has a battery and an alternator/regulator that are in parallel with each other. They are both sources of DC power. The alternator and it's rectifier/regulator work as a system that produce a regulated output voltage of 13.8 - 14 VDC. The Rotax built-in alternator has a very limited current output capability and so that regulated output of 13.8 - 14 VDC may fall below it's regulated voltage point if the ship's load is great enough.

 > 

 > One of the battery's purposes is to help stabilize the alternator's output during these peak load times. That is why you see the ammeter show a negative value at times. --The alternator is not keeping up with the power demands of the ship's power bus and so the battery is supplying the deficit power. It is suffering a net discharge.....

 > 

 > John P. Marzluf

 > Columbus C Ohio

 > Outback (out back in the garage) 

 > 

 > 

 John C

 Thanks for that reply...answered all my questions and them some! That all makes sense and is basically how I understood the system but was not sure. The fact is that I would like to be able to run my lighting C strobes and navs along with a few other things like my deicing boots and radar jamming counter measures transmitters (actually just my heater fans) so I need to get my other alternator back on and see why it is causing my oil temp gauge to fluctuate wildly. Which brings up another question (I'll make it blue text to stand out):

 Do I need another noise suppression capacitor on bolt on alternator? it is the same (or very similar) to the Rotax add-on altenator but it runs on the vacuum pump pad. It is internally regulated and rectified but does not have any internal noise suppression. I noticed that the wiring diagram in my engine installation manual shows the add-on alternator requiring a capacitor also. I ask because someone told me I didn't need one on both onboard and add-on alternators but it is there in the manual. I ordered one from John and have it so I am going to put it on unless someone can tell me why I don't need it. I get quite a bit of noise from it when I transmit...to the point that the tower has a hard time understanding. This doesn't happen when running on the Rotax generator that is on a capacitor.

 By the way C the alternator coil leads broke. The shop that rebuilt it said the original leads were very small and brittle and a couple other broke just in the disassembly. Apparently C the place that supplied the alternator did quite a bit of custom machining (custom shaft with spline gear C mount and stock mounting bracket removal) but the attachment of the coil leads was pretty crappy. They are now done with larger copper and ring terminals on each lead. It is a Nippondenso 60A alternator if you are curious but turned down like it is it only produce 30A - 40A....plenty for my bird.

 --------

 Darin Hawkes

 Series 7 

 914 Turbo

 Kaysville C Utah

 Read this topic online here:

 http://forums.matronics.com/viewtopic.php?p=244335#244335

&g========================> 

[quote] 

   	  Quote: 	
		  [b]

darinh

Joined: 20 Apr 2006
Posts: 327
Location: Utah

Posted: Sun May 17, 2009 8:15 am Post subject: Re: Charging System Theory - A few Questions

John,



Thanks again for the reply.  I liked the water bucket analogy...I am a civil engineer working in the water industry.  I can follow water because I can see it...electrons are a bit harder for me to see.

_________________
Darin Hawkes
Series 7
914 Turbo
Kaysville, Utah

Guy Buchanan

Joined: 16 Jul 2006
Posts: 1204
Location: Ramona, CA

Posted: Sun May 17, 2009 8:20 pm Post subject: Charging System Theory - A few Questions

At 10:14 PM 5/16/2009, you wrote:

  	  Quote: 	
		  Thanks for that reply...answered all my questions and them some!  That all makes sense and is basically how I understood the system but was not sure.  The fact is that I would like to be able to run my lighting, strobes and navs along with a few other things like my deicing boots and radar jamming counter measures transmitters (actually just my heater fans) so I need to get my other alternator back on and see why it is causing my oil temp gauge to fluctuate wildly.  Which brings up another question (I'll make it blue text to stand out): 	


 By the way Darin,

         I don't know if you're already doing it, but you should definitely cross-post these to the Aeroelectric List. It is also Matronics so you subscribe the same way you subscribed to this list. Unfortunately you'll get lots of chaff, but particularly if Bob Nucholls replies, you get some good wheat too.



 

 Guy Buchanan, Kitfox List Moderator

 San Diego, CA

 K-IV 1200 / 582-C / Warp / 300 hrs. and counting     [quote][b]

_________________
Guy Buchanan
Deceased K-IV 1200
A glider pilot too.

Dick Maddux

Joined: 24 Jun 2008
Posts: 516
Location: Milton, Fl

Posted: Mon May 18, 2009 4:40 am Post subject: Charging System Theory - A few Questions

Dave, Thanks for the super explanation of the electrical system ! It was  easy to understand and the electrical system is finally coming into focus !!  This has always been a problem area for me . I really appreciate all of the  replies from everyone ! It will help me analyze my own electrical  problem when it happens (at least a little bit)

                                                  Dick Maddux

                                                  Fox 4-1200

                                                  Pensacola,Fl

 A Good Credit Score is 70001367178/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=115%26bcd=Mayfooter51809NO115>See Yours in Just 2 Easy Steps!

  [quote][b]

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