> 4. Re: LiFePo4 ~ Why not move to 24 volt systems? (Alan Wilson) > > > > Message: 4 > Date: Thu, 28 Feb 2013 09:13:33 +1100 > From: "Alan Wilson" <a...@ozemail.com.au> > Subject: Re: [Aus-soaring] LiFePo4 ~ Why not move to 24 volt systems? > To: "'Discussion of issues relating to Soaring in Australia.'" > <aus-soaring@lists.internode.on.net> > Message-ID: <005501ce1537$aedee1b0$0c9ca510$@ozemail.com.au> > Content-Type: text/plain; charset="us-ascii" > > My contribution to the battery aspect of this thread is to question why we > are so infatuated by 12 volts? [I once wrote Standards, and Standards often > impede innovation] > > > > I also agree that the electrical systems must be designed and implemented > taking into consideration volts, amps, temperature high and low, wiring, > insulation, noxious gases, fusing, short circuit and thermal runaway, G > load, weight and many other factors > > > > At Oshkosh 2006 the Blue Mountains Avionics presentation said for light > aircraft the move to 24 volt systems was a no brainer, just so logical. > Most > instrumentation and radio's require 10 volts and a 12 volt system decays to > 10 volt reasonably fast. Microair's need probably 10.5 before the > transmitter goes garbled, Cambridge falls over at about 8 volts. Mike > could > perhaps comment on the minimums for Borgelt instruments. PDA's and XCSoar > have a USB 5 volt input so may work longer on a 12 volt system? Some > avionics are designed for 35 volt DC maximum input [but XCOM and Microair > apparently have 16 ~ 17 volt maximum input specification] > > > > But starting with 24 volts gets much more out of the battery before > avionics > fail. Even moving to say 16 volt to keep within radio specification could > lead to increased useful battery life. > > > > Cranking amps for starter motors is at the high drain end of the drain > spectrum but arguably is early in a batteries discharge cycle in the glider > application. > > > > So why not have 16 ~ 24 volt systems in gliders? > > > > Alan Wilson > > [ARMIT Comm Eng] > > Canberra > > > I would argue the best reason not to go to 24Volts over 12 volts would be > the option of 48 volts. > Still under the "qualified" 50 + volts for professional installation, a 48 volt system would haave many advantages over both minor voltages (and again over 6V systems, if memory goes back that far) Its no big issue to drop voltage for specific requirements, you can siphon off 5, 12 or 24 volts easily with simple electronics.
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