REFLECTOR: 24 volt electrical system

[Andrew Ellzey]

Al,

I have been looking at the Odyssey PC-680 or the PC-625 batteries also, are you charging these batteries in parallel or are you using another system such as Batterylink ACR to charge your batteries from the alternator? I also assume by your statements that you are running a 12 volt system with the second battery as a backup or standby system. Where did you buy your batteries, AS or another dealer?

Andy
  ----- Original Message ----- 
  From: Al Gietzen 
  To: 'Velocity Aircraft Owners and Builders list' 
  Sent: Wednesday, September 27, 2006 6:20 PM
  Subject: Re: REFLECTOR: 24 volt electrical system




  Since a given load draws half the current at 24 volts that it does at 12 you can use smaller wire with the same results. you can use wire that's only 1/4 the size, which is a pretty big deal when you're are running #18 and everyone else is running #14. Most small planes have nearly 50 pounds of wire in them. How would you like to save 10 pounds of dead weight?

  I'm sure 24V system has some advantages; but the 50 lb. number is way too big.  The vast majority of wires in my all electric airplane are #22.  Wires smaller than that are more difficult to work with and do not make as reliable a crimp; so even with 24v you may find that you'll want to use a least #24 or larger.  A few big ones are #18, and, of course there is the one big #2 running from contactors to starter.



  Engine start will drop a 12-volt system to around 9 volts causing EFIS systems to reboot, radios to loose presets and fuel totalizers to restart. A 24 volt system will only drop to about 18 volts during engine start, which is well above the 10.5 volt minimum for modern, digital avionics. No backup batteries, no switching, no relays, and no fiddly, complex systems to solve a non-problem.

  If my (2) PC-680 batteries are a bit low to begin with, the EFIS sometimes reboots after engine start. Otherwise no other effects.



  FWIW,



  Al



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


  _______________________________________________
  To change your email address, visit http://www.tvbf.org/mailman/listinfo/reflector

  Visit the gallery!  www.tvbf.org/gallery
  user:pw   Check new archives: www.tvbf.org/pipermail
  Check old archives: http://www.tvbf.org/archives/velocity/maillist.html
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.tvbf.org/mailman/private/reflector/attachments/20060927/2eebd8d2/attachment.htm