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I BOUGHT A BATTERY

 * September 24, 2016
 * Dave Barnhart
 * Batteries
 * 0 Comments

The Odyssey batteries cam highly recommended from a friend who operates mobile
in the boonies a lot.  Despite my earlier calculations, I decided on something
with about 45Ah of capacity.  The folks at Odyssey provide a nice detailed
technical spec.

I also liked this battery because it is small and light:

Length: 9.8″
Width: 3.8″
Height: 8.1″

Weight: 27.5 pounds

I plan to make an excursion up north in a few with for a trial run.




SOLAR CHARGE CONTROLLER FOR LITHIUM BATTERIES

 * March 24, 2014
 * Dave Barnhart
 * Batteries
 * 1 Comment

Genasun now offers a range of MPPT solar charge controllers designed
specifically for lithium batteries.

Disclaimer: I have no connection to Genasun and I have not used this product.

The offer three models:

5 amp/12V: $115
10 amp/12V: $180
350 Watt/12V/24V/36V/48V: $170

 Click Here to go to Genasun’s online store

 




ACTUAL CHARGING CAPACITY OF 20W SOLAR PANEL

 * March 8, 2014
 * Dave Barnhart
 * Getting Started
 * 1 Comment

In this photo you can see the actual rate of charge being supplied to the 12V
gel cell battery by my 20W solar panel and charge controller.

Outside air temperature is about 60 degrees. The panel is pointed directly at
the sun in a clear cloudless blue sky at about 9am.

The system (solar panel and charge controller) are producing 14.8 watts. That’s
an efficiency of approximately 75% (I suspect that figure would be higher if the
charge controller were MPPT instead of PWM).  You can see that the system is
producing 1.14A of current, which is more that what is required to
simultaneously operate the Elecraft KX-1 and charge the Kenwood TH-F6A.




LOW COST SOLAR POWERED HAM RADIO STATION

 * March 6, 2014
 * Dave Barnhart
 * Getting Started
 * 0 Comments

I’ve been able to solar-power a small ham radio station for about two hundred
dollars. The radios in this setup have relatively modest power requirements:

 * Elecraft KX-1
 * Kenwood TH-F6A 2M/440 handheld

Here is a diagram of the station’s power supply:



Solar Panel

The solar panel is a small 20W panel purchased from EcoDirect.com for $56.95
(Model VLS-20W). It is large enough to operate the KX-1 and charge the TH-F^A
continuously (when there is sunshine) and keep the battery fully charged.



Charge Controller

The charge controller is the Morningstar SG-4 PWM 4.5A Charge Controller. This
is a PWM controller so it is less efficient than an MPPT controller but in this
low-power application it will be just fine.  It also cost only $25.75.



Battery

The battery is a 7.5Ah Gel CEll.  I purchased mine from BatterySpace.com for
$18.80, but these can be found anywhere. In this application, there is nothing
magic about the capacity (7.5Ah). You’ll reliably and repeatedly get 4.5Ah out
of this battery. (For an explanation of why 4.5 instead of 7.4 Ah, read this
post.)  It contains enough charge to operate the KX-1 for about 6 hours.

Why didn’t I use a Lithium battery, you ask? Lithium batteries, preferably
Lithium Phosphate (LiPo) are much smaller and lighter.  However, most charge
controllers are intended for use with gel cell batteries. Lithium battery packs
also need charge-balancing periodically.



Power Meter/Analyzer

The Power Meter/Analyzer is from Turnigy. I bought it from Powerworx.com (the
ANderson PowerPole people) for $59.99.

Why a Wattmeter / Power Analyzer? The meter operating inline continuously allows
me to keep tabs on the battery voltage. It is really important to avoid
discharging the battery below about 11.9V (Click here to learn why). It is also
useful for measuring the actual current draw of the radios (as well as the
output fro the solar panel and charge controller). This particular meter comes
with Anderson Powerpole connectors already installed.



Connections

All connections use Anderson Powerpoles. The more I use them the better I like
them.



Radios

The Elecraft KX-1 draws about 700mA on transmit and 30mA on receive.  For the
Kenwood TH-F6A, I use its own internal batteries and recharge them from the 12V
Gel Cell.  The TH-F6A draws about 300mA while charging.




HOW MUCH BATTERY CAPACITY DO I NEED?

 * March 5, 2014
 * Dave Barnhart
 * Batteries, Getting Started
 * 0 Comments

The battery capacity you will need for your solar powered ham radio station
depends upon several factors (I’m also assuming that you will be using a Sealed
Lead Acid (SLA) battery.)

 * The radio’s current draw on receive
 * Percentage of the time you expect to be in receive mode
 * The radio’s current draw on transmit
 * Percentage of the time you expect to be in transmit mode
 * How long you intend to operate

Let’s say:

 * 2Ah on receive
 * 20Ah on transmit
 * 50% receive / 50% transmit
 * operating 4 hours per day

Since I’m in receive mode half the time, and consume 2Ah on receive, that means
I’ll consume 1 amp in receive mode per hour.

Since I’m in transmit half the time, and consume 20Ah on transmit, that means
I’ll consume 10 amps in transmit mode per hour.

My hourly current draw is the sum of those two, or 11 amps.

If I’m going to operate for 4 hours per day then I need 44Ah of capacity.

Expressed as a formula, it looks like this:

((Pr * Ir) + (Pt * It)) * Ho

Pr = Percentage of an hour in receive mode, expressed as a decimal from 0 to 1
Ir = Current draw in receive mode, in amps
Pt = Percentage of an hour in transmit mode, expressed as a decimal from 0 to 1
It = Current draw in transmit mode, in amps
Ho = number of hours of operation

Using our example of 44Ah of needed capacity, let look at batteries.  The
following chart is from solarnavigator.net:

Battery State of Charge Battery Voltage 100% 12.7 90% 12.5 80% 12.42 70% 12.32
60% 12.20 50% 12.06 40% 11.9 30% 11.75 20% 11.58 10% 11.31 0% 10.5



What this chart says is that if your battery’s voltage is 12.2V then it contains
60% of its rated capacity. It’s important to note however that if you use up
100% of the battery’s rated capacity you have killed it, meaning you have
drastically shortened its life.  In fact, to preserve battery life you never
want to get into the yellow zone in the above chart. This means that if it says
20Ah on the side of the battery it really means that you can use only 14.4Ah
(the top 60%) without permanently damaging it.

To be technically precise, this measurement should be taken when the battery is
not under load and has been resting for 3 hours, but the chart is close enough
for our purposes. Also keep in mind that the industry standard for battery
ratings is to assume that the discharge takes place continuously over a period
of 20 hours. Longer or shorter

Using our example and the above chart, to obtain 44Ah of capacity we need to buy
a battery with a capacity of 44 / .6 = 73.33Ah.

Here is the formula to account for this:

(((Pr * Ir) + (Pt * It)) * Ho) / .6

If your soar panel is simultaneously charging the battery (and if you only
operate on sunny days) then you can get by with a smaller battery. If the solar
panel and charge controller can deliver 60 watts (12V * 5 amps) to the battery,
then for each hour of operation you’ll be recharging the battery by 5 amps.  In
four hours that’s 20 amps. Theoretically then you could get by with a 53.33Ah
battery. Given system inefficiencies however that is probably optimistic. (I’ll
update this post after I run some actual real-world tests.

And one final consideration: Batteries sitting on the shelf will gradually lose
capacity over time.  Trickle chargers are inexpensive and the battery should be
kept on one when not in use.




VIDEO: PRIMER FOR SOLAR POWERED HAM RADIO

 * March 4, 2014
 * Dave Barnhart
 * Getting Started
 * 0 Comments

This is the best thing I’ve seen as an introduction to solar power for ham
radio:






ANTENNA TUNING DAY

 * March 2, 2014
 * Dave Barnhart
 * Getting Started
 * 0 Comments

The temperature was in the sixties this morning and so it was time to erect the
40M inverted Vee I built a few weeks ago and trim it to length.

I could have done the job in my backyard but decided that it was a perfect
opportunity to get out for a bit.  There is a nice park a few miles from my hows
with great views. The ramada is down in a saddle between two hills so it is a
lousy spot to try an make any contacts, but it is scenic nevertheless.

As you can see, the portable station fits in a plastic 50cal ammo can. Trimming
the antenna for resonance at the bottom end of 40M went very quickly. (An aside:
Antenna analyzers like my MFJ-269 are amazing tools. When I started in ham radio
35 years ago we had nothing like it.)

Did I make any contacts today?  No.  I didn’t expect to, given the limited time
I had, my inexperience as a QRP operator, and my lousy location.  That will
change.




ANDERSON POWERPOLES

 * March 1, 2014
 * Dave Barnhart
 * Getting Started
 * 0 Comments

I am using Anderson Powerpoles throughout this project. I became a fan of
crimp-on connectors (instead of soldered) a long time ago while building my
airplane.

A crimped connection provides much better strain relief than a soldered
connection. A crimped connection can be made miles from a source of power
required to heat a soldering iron.

I started using Anderson Powerpoles in my ham shack a couple of years ago. It
made sense to use them from the start for this project.




THE ADVENTURE BEGINS

 * February 27, 2014
 * Dave Barnhart
 * Getting Started
 * 1 Comment

Hi.  I’m Dave, WB7OBG. I live in Phoenix, Arizona where there is no shortage of
sunshine. The idea of a solar-powered ham radio station has always intrigued me.

We’re going to start out small, inexpensive and low-power.

I have an Elecraft KX-1 and currently power it from a 12V 7AH gel cell.  I’ll be
using a small (20 watt) solar panel and charge controller to charge the battery.

My handheld of choice is the Kenwood TH-F6A. Keeping things simple, We’ll be
charging it from the 12V gel cell.

From there we’ll see where solar powered hamradio it takes us.



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About Solar Powered Ham Radio
Join me as I explore powering a ham radio station vis solar power. Learn what
works, what doesn't work, and what's practical .
Contact Me
I'm Dave, K7RPM. You can find me at QRZ.com, of course. If you want to reach me
via email:
dave@davebarnhart.com

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