Information about setting up a Solar Powered Amateur Radio Station
Soon after having
written this article, I was informed that
deep cycle batteries can be discharged
regularly by about 50% or more... Wikipedia
indicates that this is the best lifespan
versus cost ratio for most deep cycle
batteries... So, I telephoned the company
again from which the battery was purchased
and was told that they recommend that
this lead acid battery shown in this
article should be discharged by about 20%
to maximize the life span of the
battery... It would pay to check the
recommendations for your particular battery...
interest nowadays in alternative forms
of power but the most popular
for Amateur Radio Operators would have
to be Solar Power...
Although I don't
know much about solar systems, I can
share with you what I do know...
There are basically
3 components to a Solar Installation... The
Battery, the Solar Panel and the Controller
to regulate the current and voltage sent
to the battery from the solar panel...
The sizes of
these depend on the amount of current
you need to draw from the battery and
the duration... Once you work out these
2 requirements, you're able to figure out
the capacities of the 3 components... In
my case for example, I operate CW on
HF so the current draw on the battery
would be about 20 Amps... By the way,
for a 100 watt radio, using Ohm's Law,
you would expect the current drawn using
a 12 volt supply to be about 8
amps or so ( 100W = 12V x 8.3A )
but because most modern solid state radios
are only about 50 or 60% efficient on
CW and a little more efficient on SSB,
the current drawn is nearly double that...
That's why most 100 watt radios which
have 13.8 volt dc power supplies are
rated at around about 20 amps or
To illustrate, let's
say the transmitter was run key down
drawing 20 amps for 1 hour. This means
that the battery has used 20 Amp Hours
in that period (20A x 1H)... Batteries are
rated in terms of their voltage and
the number of Amp Hours they can
supply... However, batteries used with solar
panels need to be of the ' Deep Cycle
' type... They should only be discharged
up to about 20% of their capacity to
extend their lifespan... If, for example,
you have a 100 Amp Hour battery, it
shouldn't be discharged by more than 20%.
ie 20 Amp Hours so that 80 Amp
Hours of the battery's capacity should still
CW using a Yaesu FT-1000MP Field.
The battery shown
in these images has a rating of 670
Amp Hours... 20% of that is approximately
130 Amp Hours... So, if the transmitter
was to run for 6 and a half
hours at 20 Amps, the battery would be
down to the allowable ' discharge level '...
There are many different types of batteries
available nowadays but I bought a 'wet'
lead acid type made by Exide in the
USA because it's a proven and reliable
type of battery, old technology... It
consists of 2 volt cells in series to
form 6 volt batteries, 2 of which make
up the 12 volt supply... A battery
this size can power a small house but
you would need a number of panels to
recharge the battery quickly due to the
regular current drain by house hold
appliances etc... The expected life span is
10 years or more if looked after
properly... ie. not run down too far
and also topped up with distilled water...
(This battery is still in use after 11
years - March 2020)...
BPSK31 using an Icom
The voltage at
the battery fluctuates depending on its
charging cycle... It may swing from 12
volts or so of a night to about
14.5 volts or so in the daytime... I
have 3 different radios that I've used
with this battery and the voltage swing
doesn't seem to affect them... The amount
of current coming from the solar panel
is dependent on the size of the panel,
it's direction towards the Sun and the
availability of sunshine... Since we're not
at the Radio QTH all the time and
drawing current, the battery doesn't need to
be charged quickly on a regular basis...
One 80 watt panel is sufficient for my
needs ie. to keep the battery charged...
The direction that the panel faces is
important to maximise the exposure to the
Sun... Also, the angle to the horizon
should be optimized to ensure that the
Sun hits the panel as near as
perpendicular as possible throughout the year,
especially in the winter... High tech panel
installations track the Sun... When mounting
solar panels (usually framed in Aluminium)
on sections of dissimilar metal, insulators
should be used to prevent corrosion at
the point of contact. I used sections
of black plastic irrigation pipe with a
hole drilled through the sides of it...
The plastic pipe is compressed when the
nuts are tightened...Stainless steel nuts, bolts
and spring washers are also recommended...
The ' Charge
Controller ' or ' Regulator ' sends the right
amount of current and voltage from the
panel to the battery... It's job is to
ensure that the battery is not overcharged,
thereby extending the life of the battery...
The panel shown, can deliver in the
order of 20 volts or so depending on
the availability of sunshine. The controller
regulates the voltage down to a charging
voltage of around 13.8 to 14.4 volts
for 'boost' charging and about 13.5 volts
for 'float' charging... These are
approximate values... When there is a large
current drain from the battery, the
regulator will allow maximum regulated current
to flow into the battery from the
solar panel... When it is fully charged,
little current is sent to the battery...
With the polycrystalline panel shown, a
maximum current of nearly 5 Amps can
be produced with a cloudless sky... The
maximum Amp Hours this panel can manage
at this QTH seems to be about 35
AH or so a day... When buying the
battery and panel, the sales people will
sell you the appropriate controller as
well... A solar controller like this one,
with an LCD screen, is able to tell
you a lot of information... eg. the
voltage at the battery terminals at present,
the amount of current going into the
battery at the moment, the number of
Amp Hours already gone into the battery
so far today, the total Amp Hours sent
to the battery each day etc... To
reduce the risk of sparking when connecting
the panel to the controller, I have
either done it of a night time or
thrown a thick blanket over the panel
consideration is the wires connecting
components... To reduce voltage drop, ensure
that you use heavy gauge wires and
also use fuses in the main lines...
Ask the sales people questions, they want
your business... By the way, it pays
to clean your solar panels regularly.
Rainwater does not do the job very
well as a film of grime builds up
on solar panels over time...
Many deep cycle
batteries can last a long time depending
on usage. If you do not demand too
much current from them, the life expectancy
of some can be ten years or more...
The battery shown in this article, as
mentioned, has been in use for about
nine years now... Although deep cycle
batteries are not cheap, once you have
a solar system up and running, there
are no ongoing power bills...
I hope this
is helpful in building your own Solar
Powered Amateur Radio Station.
Rob, VK5SW's Solar Shack. March. 2011.
Remote Radio on Receive. Dec. 2018.