[Rover] AC/DC Inverter question

Thu, 22 Aug 2002 21:01:55 -0700

Jacob,
   Another possible consideration is that every time you change from DC
to AC and back, (inverters and battery chargers) you loose some
efficiency.  By letting the 12V dc items run on the deep cycle batteries,
and just using the inverter for the laptop, I would thing the whole
system would be more efficient.  There would likely be much less RF hash
and other noise as a result of using a much smaller inverter also.  
   As others have mentioned, a battery isolator is very good insurance
that you will not strand yourself in the boonies somewhere.  It can be
either an electronic type which essentially uses a pair of diodes, or the
solenoid type which still used in many RV's.
   Contrary to another post, I have never seen one which will charge the
main battery 'first' and then charge the secondary battery.  In the  dual
diode versions there is about 0.7 volt drop across each of  diode
junctions.  So in actuality, it will begin by charging which ever battery
has  lower terminal voltage. From there on out, it is a function of 
internal resistance of the battery, which change as the battery charges. 
    The solenoid type just puts both batteries directly in parallel
(usually when something like the ignition switch is on) , and they will
equalize themselves buy virtue of the weaker battery being somewhat
charged by the stronger one.   The charging system just looks at the
terminal voltage of the combined pair.   
  In a practical sense; in either case, you probably would not be able to
tell which was being charged 'first' without some test gear. 
   The solenoid style may be a bit more efficient from a battery charging
standpoint, but is a bit less foolproof, because if you have to leave the
ignition switch of for some other reason (or forget it is on), you can
run down both batteries at the same time.  The electronic (dual diode)
version makes it nearly impossible for this to happen.   

Rod Johnson  WE7X (ex KA7YOU) Grid CN97AL - near Issaquah, Wa

On Thu, 22 Aug 2002 16:10:53 -0400 "Jacob Tennant" <[email protected]>
writes:
>Yes, my radio & amp both run off of 12Vdc. However I was thinking it 
>would
>be nice to have the PS's with me and connected 24/7 so as to be able 
>to
>swith over to a generator when sitting still, AC power ready at home. 
>Plus I
>need to get a inverter for the laptop anyway so was thinking I would 
>just
>kill 3 or 4 birds with one stone.
>
>Was hoping to run all of this off of a second battery anyway that 
>would be
>independent of the vehicles charging system. On charge via small 
>generator
>when stopped or at home for the night.  Daily use would only be for 2 
>to 3
>hours at a pop.
>
>Jacob Tennant  K8JWT
>----- Original Message -----
>From: "Thomas Jennings" <[email protected]>
>To: <[email protected]>
>Sent: Thursday, August 22, 2002 8:07 AM
>Subject: Re: [Rover] AC/DC Inverter question
>
>
>> Jacob,
>> I would recommend that you us a true sine wave inverter with a power
>> rating of over 1000 watts or more.  We found that if the inverter 
>gets
>> loaded it generates lots of noise and spurs.
>> But doesn't you rig and amp run off of 12v?
>> Also check if your computer is noise on the bands you will be using
>> while roving.
>> Good luck and 73
>> Tom kv2x
>>
>> Jacob Tennant writes:
>>
>> > Looking into a power inverter to run my radio system out of my car 
>with.
>> >
>> > Trying to figure out how big of one do I need?
>> >
>> > Radio=10watts RF
>> > Amp=160watts RF
>> > Laptop=57watts AC
>> >
>> > So what size? 300watts, 700watts, 1000watts?
>> >
>> > Presently I have a 15amp power supply but was looking at a 25amp 
>power
>> > supply to run the radio & amp, as for now I only have 6meters, but 
>plan
>to
>> > get other bands as I can via transverters along with 100+watt amps 
>for
>each.
>> >
>> > My ultimate goal is to make the system as easy to take into the 
>house or
>> > other site as possible yet still be a good mobile setup.
>> >
>> > Have the radio mounted on top of the present power supply so as to 
>use
>in
>> > the house as well as mobile mouted via floorboard & a couple of 
>load
>hauling
>> > straps around the car seat frame, using the PS as a riser to bring 
>the
>radio
>> > up to a useable level off of the cars floor. Also looking at 
>mounting
>the
>> > amp on top of the radio for convienence.
>> >
>> > HELP! ! !
>> >
>> > Jacob Tennant  K8JWT
>> >
>> > _______________________________________________
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>> > [email protected]
>> > http://mailman.qth.net/mailman/listinfo/rover
>>
>>
>>
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