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12 Volt .vs. 24 Volt

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bwolf1(at)tds.net
Guest

Posted: Mon May 18, 2009 5:42 am Post subject: 12 Volt .vs. 24 Volt

I have a feeling that this subject has been discussed before, but I  

need help deciding on a voltage system for my Velocity.  I intend a  

robust electrical system to support a high end IFR panel.  The highest  

draw item will probably be an electric hydraulic pump which pulls  

about 30 amps at 12 volts.  I know a 24 volt will save some weight in  

wiring because of the lower amperage.  However, after reading Bob's  

response to a Blue Mountain article



http://www.aeroelectric.com/articles/richter/response_1.pdf



the weight saved appears minimal.  I don't know for sure, but I have a  

feeling that the vast majority of OBAM airplanes are built around 12  

volt systems.  My question is, why do the likes of Cessna and Cirrus  

build their single engine airplanes with 24 volt systems?



Thanks...Brooke

Bruce(at)glasair.org
Guest

Posted: Mon May 18, 2009 6:25 am Post subject: 12 Volt .vs. 24 Volt

Similarity of construction.



Bruce

Glasair III (28v)

www.Glasair.org 



--

Peter Laurence

Joined: 10 Jan 2006
Posts: 50

Posted: Mon May 18, 2009 7:33 am Post subject: 12 Volt .vs. 24 Volt

 	  Quote: 	
		  


	


I have a feeling that this subject has been discussed before, but I  

need help deciding on a voltage system for my Velocity.  I intend a  

robust electrical system to support a high end IFR panel.  The highest  

draw item will probably be an electric hydraulic pump which pulls  

about 30 amps at 12 volts.  I know a 24 volt will save some weight in  

wiring because of the lower amperage.  However, after reading Bob's  

response to a Blue Mountain article



http://www.aeroelectric.com/articles/richter/response_1.pdf



the weight saved appears minimal.  I don't know for sure, but I have a  

feeling that the vast majority of OBAM airplanes are built around 12  

volt systems.  My question is, why do the likes of Cessna and Cirrus  

build their single engine airplanes with 24 volt systems?



Thanks...Brooke



I wired a Velocity XL RG for a friend as a 12v system. Dual B&C alternators

and Regulators.



No issues for over four years and five hundred hours.

Peter

skywagon

Joined: 11 Feb 2006
Posts: 184

Posted: Mon May 18, 2009 8:30 am Post subject: 12 Volt .vs. 24 Volt

Why 24 v. systems.... in the commercial world it is usually about costs and 

profits.  Less copper used, less cost.

David

---

mrspudandcompany(at)veriz
Guest

Posted: Mon May 18, 2009 9:03 am Post subject: 12 Volt .vs. 24 Volt

Similarity of construction.



	(Please elaborate!)

Bruce

Glasair III (28v)

www.Glasair.org 

I have a feeling that this subject has been discussed before, but I  

need help deciding on a voltage system for my Velocity.  I intend a  

robust electrical system to support a high end IFR panel.  The highest  

draw item will probably be an electric hydraulic pump which pulls  

about 30 amps at 12 volts.  I know a 24 volt will save some weight in  

wiring because of the lower amperage.  However, after reading Bob's  

response to a Blue Mountain article



http://www.aeroelectric.com/articles/richter/response_1.pdf



the weight saved appears minimal.  I don't know for sure, but I have a  

feeling that the vast majority of OBAM airplanes are built around 12  

volt systems.  My question is, why do the likes of Cessna and Cirrus  

build their single engine airplanes with 24 volt systems?



Thanks...Brooke

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nuckolls.bob(at)aeroelect
Guest

Posted: Mon May 18, 2009 10:29 am Post subject: 12 Volt .vs. 24 Volt

At 10:44 AM 5/18/2009, you wrote:

 	  Quote: 	
		  



Why 24 v. systems.... in the commercial world it is usually about 

costs and profits.  Less copper used, less cost.

David




	


    Close. When I went to work for Cessna in '64, we had

    14v airplanes (150, 172) and 28v airplanes (182, 206,

    210). When you need to run high-energy electro-whizzies

    you can get more WATTS of engine driven power from

    essentially the same WEIGHT of system if it's 28v.

    But as quantities of all airplanes sold dwindled,

    it was economically more efficient to simply install

    the same hardware in all aircraft. The alternators

    were the same size and weight, batteries could be

    sized to the task for total energy stored. Common

    landing lights, nav lights, strobe kits, etc made

    for fewer line items of electrical goodies in

    inventory and more wider applicability of fewer

    parts for field spares.



    It had nothing to do with any practical level

    of weight savings. We kinda like 14v stuff in the

    OBAM market: unlike the uniquely aircraft

    "pallet of paints" for 28V hardware, 14V automotive

    hardware is stocked in thousands of varieties and

    sources virtually everywhere on the planet.



    The "improved performance" and "lighter weight"

    canards are difficult to measure/prove without

    carefully detailed studies with slice-n-dice

    instrumentation. For us get-in-n-go airplane

    drivers, the 14 vs. 28 volt differences are

    not readily observable. So the big driver is

    simply cost of ownership in terms of $acquisition$

    and $time$ to maintain. 14v has it hands down.



        Bob . . .



        ----------------------------------------)

        ( . . .  a long habit of not thinking   )

        ( a thing wrong, gives it a superficial )

        ( appearance of being right . . .       )

        (                                       )

        (                  -Thomas Paine 1776-  )

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

BobsV35B(at)aol.com
Guest

Posted: Mon May 18, 2009 10:53 am Post subject: 12 Volt .vs. 24 Volt

Good Afternoon,

  

 Definitely NOT 'Lectric Bob here!

  

 I DO like twenty-four volt systems. I also agree that any weight saving is  probably minimal on an overall basis, nevertheless, I do subscribe to the theory  that ounces count. 

  

 Twenty-four volts allows us to use lighter weight starters, alternators,  wires, even relays. The trouble is that most twenty-four volt units weigh as  much as their twelve volt counterparts. If you want to take full advantage of a  twenty-four volt system you also have to use lighter components. If thirty  amps at twelve volts will handle all of your aircraft requirements, all you need  is fifteen amps with a twenty-four volt system. How many fifteen amp alternators  do you see available? 

  

 If you go ahead and use a thirty amp twenty-four volt alternator, you have  not taken full advantage of the weight saving capabilities of the twenty-four  volt regime.

  

 Cessna went to twenty-four volts for everything from the 152 on up many  years ago. It was cheaper and lighter for the whole fleet and only having to  deal with twenty-four volt components made inventory control a lot easier.

  

 Commonality of parts and all of the economies that breeds!

  

 If you want to be able to jump start your airplane form a twelve volt car,  twenty-four volts may not be for you.

  

 Personally, If I ever have the feeling that I need a jump start for my  airplane, I would also determine that I had made some sort of error in managing  my flying machine. 

  

 If I leave the master on and deplete the battery, I will pull the battery,  have it properly serviced, and chalk the experience up to my own stupidity. (I  have, unfortunately for me, had to do that more than once.) 

  

 What I have NOT done, however, is jump start my airplane!  If I need  the battery at all, I want it to be fully charged and properly serviced before I  fly.

  

 Happy  Skies



Old Bob

AKA

Bob Siegfried

Ancient Aviator

628 West 86th  Street

Downers Grove, IL 60516

630 985-8502 

Stearman  N3977A

Brookeridge Air Park LL22   

  In a message dated 5/18/2009 12:07:06 P.M. Central Daylight Time,  mrspudandcompany(at)verizon.net writes:

  	  Quote: 	
		  

Similarity of construction.



    (Please    elaborate!)

Bruce

Glasair III (28v)

www.Glasair.org 

I    have a feeling that this subject has been discussed before, but I     

need help deciding on a voltage system for my Velocity.  I intend    a  

robust electrical system to support a high end IFR panel.     The highest  

draw item will probably be an electric hydraulic pump    which pulls  

about 30 amps at 12 volts.  I know a 24 volt will    save some weight in  

wiring because of the lower amperage.     However, after reading Bob's  

response to a Blue Mountain    article



http://www.aeroelectric.com/articles/richter/response_1.pdf



the    weight saved appears minimal.  I don't know for sure, but I have a     

feeling that the vast majority of OBAM airplanes are built around 12     

volt systems.  My question is, why do the likes of Cessna and    Cirrus  

build their single engine airplanes with 24 volt    systems?



Thanks...Brooke



	




 A Good Credit Score is 700 or67178/aol?redir=http://www.freecreditreport.com/pm/default.aspx?sc=668072%26hmpgID=115%26bcd=Mayfooter51809NO115>See Yours in Just 2 Easy Steps!

  [quote][b]

lists(at)stevet.net
Guest

Posted: Mon May 18, 2009 12:44 pm Post subject: 12 Volt .vs. 24 Volt

And don't forget to add that you can save much more weight in the  

operation of your aircraft by going on a diet!  Drop 10 to 15 pounds  

off your personal frame and it will make up for many many incremental  

weight saving devices in your airframe.

Steve

________________________________________________________________________



On May 18, 2009, at 11:23 AM, Robert L. Nuckolls, III wrote:



 	  Quote: 	
		   The "improved performance" and "lighter weight"

   canards are difficult to measure/prove without

   carefully detailed studies with slice-n-dice

   instrumentation. For us get-in-n-go airplane

   drivers, the 14 vs. 28 volt differences are

   not readily observable. So the big driver is

   simply cost of ownership in terms of $acquisition$

   and $time$ to maintain. 14v has it hands down.



       Bob . . .

Bruce(at)glasair.org
Guest

Posted: Mon May 18, 2009 1:40 pm Post subject: 12 Volt .vs. 24 Volt

Sorry, poor choice of words on my part. What I meant was "Commonality of

Manufacturing". It easier for the factory to use one battery, one relay,

one bulb, one starter, across the entire line than a mixed bag for each

different aircraft.



Where 28v has 14v beat is in delivery of power. I remember flying my 14v

C177RG at night with everything, including all the lights turned on.

When I reached for the gear lever and flipped it down, everything went

dim! Just about every 14v RG airplane I've flown does that. Not the 28v

ones, just the 14v. Power, when you need it, you need it!



Bruce

www.Glasair.org 



--

rtitsworth

Joined: 16 Jan 2006
Posts: 76
Location: Detroit, Mi

Posted: Mon May 18, 2009 5:12 pm Post subject: 12 Volt .vs. 24 Volt

If you're thinking heated prop, Elec air conditioning, Elec cabin heat,

heated seals, or other high-energy goodies, then a 24V system/alternator

offers twice the "power" for roughly the same system weight as a 12v

alternator.  It's not the (potential) smaller wire savings that is

significant/relevant, rather it's twice the available power from the same

weight alternator, contactors, etc (i.e. the heavy items).



This is also perhaps a consideration if you're planning on a small backup

(B&C type) alternator.  The 24v version again has twice the available

"power" as the 12v (same weight/package) - i.e. more things you can drive on

the E-bus.



It used to be that 24V goodies were hard to come by.  However, an evening

with an aircraft spruce (or west marine) catalog will revel that many common

items are now available 12v or 24v (14/2 for the same price.  More over,

most modern avionics items now operate over the entire 12-28 range.



With some "shopping", perhaps the only items that needs converting down to

12v is the cigarette lighter port and Ray Allen trim tab servos.



.02

--

bwolf1(at)tds.net
Guest

Posted: Tue May 19, 2009 2:36 am Post subject: 12 Volt .vs. 24 Volt

Thanks to everybody for their comments.  It is much easier to make  

informed decisions when armed with the insight that this group  

provides.  Thanks to Bob and everybody else for making this possible!



Brooke

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