[Elecraft] Mobile from 117 VAC

[K9MA]

Most likely, the AC inverter built into the car does not produce a sine 
wave, and your radio probably won't like it.

You could just connect some heavy wire, with a fuse, directly to the 
battery terminals, and run the radio on that.  However, car batteries 
don't deep cycle well at all, and there's the chance of not being able 
to get the engine started.  You can buy a small, 30 AH deep cycle 
battery, which will run a 100W radio for some hours of normal 
operation.  A voltage booster will step the voltage up to 13.8 V, so the 
transmitter will operate at full power.  One big advantage of the 
separate battery is that you can carry it a ways from the parking lot if 
you have to.

Charging the battery from the vehicle is a bit tricky, though. You can't 
just connect it in parallel with the vehicle battery, as the alternator 
will charge it at much to high a current.  I was unable to find an 
affordable commercial device that could safely charge such a battery 
from the vehicle.  One could build a current limiter, but it would take 
some effort.  For me, the path of least resistance was to buy a 120V 
battery charger, and run it on a 150W sine wave inverter I already had.  
(Using the above connections to the vehicle battery; that's a bit much 
for the cigarette lighter plug.)  Such a charger may or may not work 
with the built in inverter in the vehicle.

73,
Scott K9MA

On 10/8/2017 22:19, Dauer, Edward wrote:
> Previous threads provided a great deal of info about arranging automobile electrical systems to power HF rigs.  But as I recall, it all focused on using the battery / alternator supply for the 13 VDC.  Though I wanted to go mobile and still do, for a number of reasons I could not configure my car to do it properly.  I am now thinking of buying a new SUV which has 117 VAC outlets in its rear cargo space.  That makes me wonder – could I just use an ordinary 117 VAC to 13 VDC power supply, exactly as I do at home, just plug it in and – staying within the car’s rated current draw – operate without worrying about where the ground goes vis-à-vis the battery, what-all needs to be bonded with what-all-else, how everything needs to be mummified in ferrite, etc?  Or are the problems all the same even though different?  My objective is simple.  I want to be able to drive to a rare county, set up my buddipole in a parking lot, and use either a XX3/KXPA or a K2/100 to knock out some CW QSOs.  I do NOT want to take an electric drill or a rivet gun to a new car.
>
> Has anyone gone mobile using a car’s 117 VAC outlets?  Any thoughts to share?  Any thoughts from anyone who for any reason hasn’t done it?
>
> Ted, KN1CBR  (operating this week as N0A in the NAQCC anniversary event.  Give a call if you hear me.  Mostly 20 or 40 CW)
>
> Tnx.
>
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-- 
Scott  K9MA

k9ma at sdellington.us