Been there do FD every year as solar since 2004.
Field day based on more than a decade of doing solar for 100W
VHF station. The 100W is from Tentec 6n2 (20w radio) and a pair
of bricks. Bricks are run at less than max unless required and
off for the night time to preserve battery (66ah).
NOTE: I run my Home station fully off grid with a solar system
charging an industrial 150Ah Flooded NiCd stack for the last
decade. Leading up to that many more years of experience
with smaller lead and under 100W solar. Please no comments
on NiCd charge efficiency, they were near new and free. The
charge controller is my design as with 600W of solar now, no
one made one then with the right profile for NiCd that didn't
wipe out HF. The upside is 10 cells of wet Nicd has a standing
voltage above 12V, typically 13.8-14.8.
So experience and having done something(s) wrong the first
few times speaks.
Test at home first! Hook it up and run for a few hours. That means
the setup (hookup and initial power on) how the radio behaves
with and without sun. Is a battery boost controller needed?
are the connectors solid and polarized adequately.
The MPPT controllers get the most of the panel(s) into the battery
but noise for many is an issue. Next best is PWM you generally
loose 15% of total charge capacity but most are silent.
Morningstar is my first pick for controllers for lead based cells.
If your pocket can afford it excess charge capability is good to the
limit of what the battery can stand (peak current). as in 400W
means 22A in hard sun (#10wire minimum and thicker). Battery
has to tolerate at least 30A charge rate (400W +MPPT).
Oh 400W of panels is not light! they are about 16-17pounds each.
Also any rigging needed to make them fast the sun.
Use thick wires as I^R costs charge power! That includes from
the panels to charge controller, battery, and hence to the radios.
FUSE everything, redundantly! Also insure nothing can be
connected backward. Also never run direct from solar as open
circuit and light load is typically 18 to 21V, deadly to most radios.
MPP voltage is 17-18V for most panels at rated power!
For a 100W station you need enough battery for the overnight typical will
be 100AH with a DC boost or a radio that tolerates 11V. Lead when
not under charge will sag to under 12V. Use very heavy cables
from battery to radio (#12 minimum, #8 is not unreasonable).
Put bluntly you want watt-hours from the battery and a 100AH
battery is good for maybe 650WH (to 40% depth of discharge).
Bigger is always better.
To keep it charged during the day for typical HF SSB/CW station
between 200W of solar is enough (depending on RX/TX duty cycle).
Keep in mind you want to have a maximum charge current below
the max charge rate for the battery C/5 MAX or about 20A (about
250W for about 100AH). Too much current and they battery heats
and boils off electrolyte (Fatal for gell/AGM). Also the radio only
wants about 240W peak at 100W and more like 20-30W on RX.
The charge controller can help with that but only to a point.
If your adding computers and lights, add battery and solar accordingly.
Try to not use 12v to 120V inverters, they can be noisy and on a
good day maybe 70-80% efficient (wasted power). Some claim
higher but at some specific load and at low power loads the
efficiency goes down. Count on less, hope for more.
Charge controller Morningstar has worked for me and HB design
as well (Not MPPT). Renology, too noisy, I tried a few of theirs.
At 100W but reduced input when not needed as a scaled
to smaller station. Battery at 66AH of battery, 130W of
solar and Morningstar. The solar was 3x 20W parallel
(Morningstar sunsaver) and a 70W with same. They
are not MPPT they are PWM so they are small and
very quiet and seem to work well in parallel. Overnight
ops are at 20W output. FD that way works at VHF as
antenna makes up for it (yagies). Or HF as QRP
(reduced power).
Either way the panel must face the sun for full output,
and moved from eastward to westward to get the maximum
exposure for the day (maximize solar hours). Shade and
more than 60 degree off angle seriously reduces power out.
Battery must be able to support peak load and no sun time
(over night at minimum) here in the northeast that means
charge the battery with solar before FD in case of rain.
On a rainy day expect 3-10% of possible power, variable
due to how overcast as daylight is not direct sun.
Backup is small genset (800-1000W or so) and a decent
8-10A battery charger or genset that has battery
charging capability. If you have wind...
Allison