That's right, absolutely NAC. Electrical question

[Richard J Lebens]

Start out in a perfect world - 100% efficiency.  The rated output of the supply is 24 @ 3.75 Amps which works out to 90 Watts.  (It probably does not run at it's rated output)  90 Watts at 12 volts will require 7.5 Amps.  8 hours would use 60 Amp-hours which seems to be within a 12 volt deep cycle battery capability.

Now the real world   Guess (I have no clue) that the 24 volt supply is 85% efficient, the inverter 60% which will require 177 Watts at 12 volts or 14.7 amps, beyond the capability of a battery.  Now if the device only needs half that 3.75 Amps you have a much better situation.

Of course a boost regulator that gets rid of all that inefficiency would work a lot better but that would cost money.

Somebody check my math.

   1. NAC.  That's right, absolutely NAC.  Electrical question

      (John Larson)
So I have this former customer, a charity case, pretty much, with a 
sleeping/breathing problem.  He lives in a 1970 VW bus with only 
occasional access to 110v power.  He uses a respiration helper device 
when he sleeps.  I have the label for the power supply (which has a 24v 
output at 3.75A), and I need to figure out what kind of load that'll put 
on a 12 battery through a 400w 90A inverter.  He already has the 
inverter so we want to try to use it.  I'm planning to install some kind 
of battery isolator, possibly a Ford starter relay (of which I have a 
number) activated by the KOEO position on the ignition switch.  If it 
would be better, I can purchase a dedicated component.  I'm planning on 
using a deep cycle battery and keeping it charged with the alternator 
(and possibly a solar panel, if necessary).  I know there are some of 
you that can do the math while walking and chewing gum, so this one 
should be a breeze!  I'm not one of those people ...................  
Would it be better to just use a 12vDC>24vDC device and forgo the 
12vDC>110ACv>24vDC?

Cost effective way?  Best way?

Thanks!  John



_______________________________________________
quattro mailing list
quattro at audifans.com
http://www.audifans.com/mailman/listinfo/quattro