REFLECTOR: 24 volts vs. 12 volts -- Important 'Upside'

[Wayne]

Buying 24 V alternators and 24 V batteries is way more than twice as 
expensive as 12 V stuff, if that matters.
----- Original Message ----- 
From: "Jim Agnew" <jim_agnew_2 at yahoo.com>
To: <bobj at computer.org>; "Velocity Aircraft Owners and Builders list" 
<reflector at tvbf.org>
Sent: Monday, January 24, 2005 8:47 AM
Subject: RE: REFLECTOR: 24 volts vs. 12 volts -- Important 'Upside'


> Not true, an alternator requires cooling for the heat produced in direct
> relationship to the watts produced.  12V x 50A = 600 watts = 24V x 25A. 
> If you
> have the same amperage output at 24V you have a 120W alternator.
>
> Jim
> --- Bob Jackson <bobj at computer.org> wrote:
>
>> An important 'upside' of 24v. is that it also effectively doubles an
>> alternator's current output capacity, usually with little, if any, 
>> increase
>> in weight.  Having extra amperage available will be important to us to 
>> use
>> for seat heaters (and possibly electrical heaters) for a warmer cabin 
>> during
>> long flights at high cruising (cold) altitudes.
>>
>> Bob Jackson
>>
>>       ----- Original Message -----
>>       From: Douglas Holub
>>       To: Velocity Aircraft Owners and Builders list
>>       Sent: 1/16/2005 9:11:08 PM
>>       Subject: Re: REFLECTOR: 24 volts vs. 12 volts
>>
>>
>>       If anyone is interested, I did some calculations: 30 feet of 2 AWG
>> wire weighs 6 lbs, and will drop .468 volts with a 100 amp load; 30 feet 
>> of
>> 4 AWG wire weighs 3.78 lbs and will drop .373 volts with a 50 amp load.
>>
>>       Doug
>>         ----- Original Message -----
>>         From: Joe
>>         To: Velocity Aircraft Owners and Builders list
>>         Sent: Sunday, January 16, 2005 10:13 PM
>>         Subject: Re: REFLECTOR: 24 volts vs. 12 volts
>>
>>
>>         Doug,
>>         No real downside if all the components you use are rated for 24v
>> (radios etc.)  You will need speed brake and trim actuators for 24v or 
>> build
>> a voltage divider into those circuits.  I was going to go 24v myself, but
>> since I am doing an auto conversion finding a 24v starter and/or 24v ECU
>> made it easier to stay 12v.
>>
>>         Be careful with your statement about wires being smaller by 1/2,
>> wire size to current capability is not linear.  The wire length also has 
>> to
>> be included into wire sizing so that there is no more than a 0.5v drop on
>> 12v circuits and 1.0v on 24v circuits.  AC 43-13 is a good source for 
>> sizing
>> wire in aircraft applications.
>>
>>         One possible downside, if you want 110 vac power for say a laptop
>> computer, you might have a hard time finding a 24V inverter.
>>
>>         Joe
>>           ----- Original Message -----
>>           From: Douglas Holub
>>           To: reflector at tvbf.org
>>           Sent: Sunday, January 16, 2005 10:37 PM
>>           Subject: REFLECTOR: 24 volts vs. 12 volts
>>
>>
>>           If I have a 24 volt system I'll use half the current so my 
>> wires
>> can be smaller by 1/2 and I'll save a pound or two. What's the downside?
>>
>>           Doug
>>
>>
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>
> =====
> James F. Agnew
> Jim_Agnew_2 at Yahoo.Com
> Tampa, FL
> Velocity 173 Elite Aircraft Completed & Flying
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