[aprssig] Tesla Field Day mode (reducing the 250W overhead)

Robert Bruninga bruninga at usna.edu
Tue Mar 26 13:50:33 EDT 2019

Found this in my DRAFTS box, so sending it now.

Yes, 24 hours of battery operation for Field Day from an EV or
plugin-hybrid can work well!  90% of all FD entries operated at 150W or

N8HKU author of the QST article on running an event for 5 hours reports
that his plugin-hybrid's overhead was about 250W (like the Prius too) and
the station only drew about half that.  He could have done that for about
12 hours before the engine would start.

So the solution to lasting all 24 hours is to only run the FD station as
normal from the 12v car battery (with any inverters needed) with the "HV
system" OFF, and then only power-up the car periodically to recharge the
12v battery.  This would drastically reduce the lost 250W overhead power,
and more than double the duration to last the full 24 hours of Field Day
but It would need constant monitoring of the 12v battery to know when to
power up the car's HV DC/DC converter system to recharge it.

But this way, even the small 5.5 kW battery in a plugin-hybrid would last
the full 24 hours of Field Day and meet the rules of not charging by gas.
Oh!  And also this allows for the addition of a 12v solar panel to help
along with no special additional hardware.  My take would be to bring a
separate 12v battery for FieldDay loads so as to not risk running down the
Plug-in hybrid EV.  Then parallel it with the car every few hours when it
is time to charge.

This x5 all-battery multiplier for all contacts for all 24 hours is nice
for score counters...  And only takes a minimum of solar panels if at all.


-----Original Message-----
Subject: Re: [aprssig] Tesla Field Day mode (versus the rules)

>> As to power, it looks like operating at more than 150 Watts divides
>> all scores in half, and so generally  it is unlikely that many
>> stations haul out kW linears to Field.

> That might explain why our score went UP in the last few years
> despite (or presumably BECAUSE OF) losing a kilowatt station.
> He used to score a lot more than any of the rest of us,
> but not more than the rest of us ALL ADDED TOGETHER   :-D

>> A plugin hybrid with 20 times the battery capacity has been
>> demonstrated to run a poertable operation for 6 hours and still only
>> used half the battery capacity without an engine start.

Yeah Pat's Outlander was 17hrs to use 80%, at which point the
engine/generator kicks in for about 20 mins to recharge it. Didn't last
the whole weekend though.

> So it looks like this topic is worthy of a closer look to all the
> details and nuances against the variety of rules to optimize the

We're one of those "have fun" FDs rather than point-pinching. It was fun
to prove we COULD operate at least 2 stations and a shelter for 17hrs on a
PHEV battery alone, and an estimated 10 days on a PHEV with a full tank of

"Nosey" Nick Waterman, VA3NNW/G7RZQ, K2 #5209.
use Std::Disclaimer;    sig at noseynick.net
I can please only one person per day. Today is not your day.

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