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

[Jim Agnew]

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