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Relatively Easy Solar Power

from Kenneth M. Beck, WI7B on August 6, 2012
View comments about this article!

"Editor's Note: Due to the popularity of some of eHam's older articles, many of which you may not have read, the team has decided to rerun some of the best articles that we have received since eHam's inception. These articles will be reprinted to add to the quality of eHam's content and in a show of appreciation to the authors of these articles." This article was originally published on: 04/04/2009

Relatively Easy Solar Power
Running your station HF and VHF/UHF radios on renewable solar energy.

The point of this short article is to show that a station based on renewable solar power is within the reach of any radio amateur for the price of a mobile rig and, honestly, minimal effort.

I've taken a 15 Watt amorphous silicon solar panel (shown above) and fitted it to the metal roof above the shack. It's used to trickled-charge a 12V deep-cycle battery. Diode-blocking protects the panel from reverse current as the battery reaches full charge.

In direct sunlight, the panel produces 20V unloaded. However, it is able to provide charge even in overcast and rainy conditions. It was purchased from Silicon Solar for under $120.

The deep-cycle 12V 33 amp-hours (AH) SLA absorbed glass matt (AGM) battery with the finished wire set is displayed above.

Although it is capable of working in a range of temperatures, maximum efficiency is maintained by keeping the battery inside. AGM technology allows 99% of produced hydrogen and oxygen gases to recombine in the battery, while acid leaking is mitigated. It was purchased at a Battery-Plus mall outlet for under $80.

In typical use, the battery is charged-up by a mean 10% of its AH capacity per day. This allows just under 10 minutes of 100% transmit capacity at 100W on my Kenwood rig for total renewal. For emergency use (non-diurnal renewing) this can be extended to 60% of battery capacity (19.8 AH) or about 55 minutes of transmit without detrimental effect.

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Relatively Easy Solar Power  
by AA4PB on August 6, 2012 Mail this to a friend!
For continuous, unattended charging I'd recommend the addition of a charge controller to prevent possible over-charging of the battery.
Relatively Easy Solar Power  
by W4KYR on August 6, 2012 Mail this to a friend!

One can buy one of those 3 solar panel set from Harbor Freight for under $200 if on sale. It includes a charge controller and a couple of lights.

Solar panels are a good alternative energy source, but in most cases they are dependent on batteries. Deep Cycle batteries are a must.

Although a riding lawn mower battery will do in a pinch if you are constantly charging it while using the radio. Keep in mind that after some time (a few years) the batteries will have to be replaced.

Never connect a radio directly to a solar panel as they put out 17 volts or more.

Most of today's radios will be OK with the high side of 12 volts, but after awhile the rig may start having issues from the lower power as the battery drains.

Some radios may not perform well with 12.3 volts when it requires 13.8. Look into a voltage booster to take the 12+ volts and convert it to a steady 13.8 volt output.

All hams should start somewhere with solar, even if it is just a couple of AA rechargeable batteries and a AA solar charger.

Cost? You can do ok with solar for a price of a HF rig. Two Harbor Freight(3 panel)sets for $200 X 2 = $400, two deep cycle battery group 27 $70-$80 x 2 = $160 , voltage regulator $100. $660 total.

You might wish to invest in a couple of extra panels and keep them in storage if you do decide a permanent installation. You will use them to replace the ones damaged by hail or wind.

I don't suggest in getting an inverter unless you get a pure sine wave one. The modified sine wave inverters can do damage with sensitive electronics.

The use of inverters with a solar panel system adds to the cost, but gives more flexibility in the long run. You might need extra panels, batteries and a larger charge controller.

Many people have started out in solar with nothing more than just a solar panel. Regardless, get a decent a charge controller.

Relatively Easy Solar Power  
by N6DMR on August 6, 2012 Mail this to a friend!
The Harbor Freight 3 panel unit is on sale now for $159.95, it is a 45 watt setup.

I run a 130 watt panel on my motorhome thru a charge controller. This is about 15 amps. I found that the solar charge controller does a better job of bringing my batteries up to peak (14.2 volts).

I have my Flex 5000 direct and my laptop powered off the 4 deep cycle batteries in my coach via a 1000 watt inverter. I have about 480 amphours but I try to not drain the batteries more than 40% - 50% so in real time it is about 200 amphours.

Duane N6DMR
Relatively Easy Solar Power  
by KC5EZ on August 7, 2012 Mail this to a friend!
Just got mine hooked up. During the day 14.5 volts, at night using HF and VHF at the same time 12.6V. Never gets below 12.3V. Harbor Freight might be good, but I think is a better deal. You get 4 panels and a voltage inverter for $60.00 more. Take your Ham Shack OFF the power grid and be environmentally friendly!

Relatively Easy Solar Power  
by K0JEG on August 7, 2012 Mail this to a friend!
The Harbor Freight 45W kit is OK, but takes up a lot of room for the power generated. You can get more power output in a single panel with something like this:

However it doesn't come with the "controller" or the really ugly florescent lights. And the controller on the Harbor Freight kit doesn't do anything to protect your battery.
RE: Relatively Easy Solar Power  
by K0IZ on August 7, 2012 Mail this to a friend!
With a 15 watt panel (rated at 17 volts), really more like 11 watts or so), that's about 1 ahr charge. Really don't need a controller for that (would take a month to charge from flat battery). Obviously higher power panels, or smaller batteries, would benefit from controller.
Relatively Easy Solar Power  
by KK5JY on August 7, 2012 Mail this to a friend!
I would echo those who have said to use a charge controller. If the panel is small, it might have a difficult time overcharging a large AGM battery, but if you have enough panel power to charge the battery quickly, you have enough panel power to overcharge the battery. Even AGM batteries will outgas hydrogen if you overcharge them.

You can buy simple on-off charge controllers that cut in at 14 volts, and out at 13 volts; these are available on Amazon for less than $20. This is really cheap insurance for your battery and your house.

Charge controllers that will do a proper charge sequence on your battery (bulk charge, absorption, trickle, and sometimes equalize) can be had for around $35 for 10A models.

There is an entirely new breed of charge controllers out there that will track the maximum power point of your panels, and convert excess voltage into current for you. Since most 12V panels have a maximum power point near 20V, this is a really nice feature. These controllers are called MPPT controllers, and are not cheap. But they are very cool. In a multi-panel solar array, an MPPT controller can harvest enough additional energy from the panels to be equivalent to adding a panel or two.

Even if MPPT is outside your price range, I would highly recommend a simple smart charge controller, such as the SunForce digital charge controllers. They will make your battery last much longer.

For a good discussion on how deep-cycle batteries should be treated for maximum service life, see one of the many good sites on that subject. Here's an example:

K0BG's mobile ham radio site also has some good information about using batteries to power ham gear.
Relatively Easy Solar Power  
by REMOVED_ACCOUNT_2015-01-09 on August 8, 2012 Mail this to a friend!
Have purchased their products before. Excellent.
RE: Relatively Easy Solar Power  
by AA4PB on August 8, 2012 Mail this to a friend!
K0JEG: "the controller on the Harbor Freight kit doesn't do anything to protect your battery."

Why do you say that? I don't have any direct experience with that kit, but in the manual on the Harbor Freight web page it looks like a "real" charge controller that would limit overcharging of the battery.
RE: Relatively Easy Solar Power  
by K0JEG on August 8, 2012 Mail this to a friend!
AA4PB, it looks like they updated the controller box, at least on the output side. I'd like to see what's inside before using it though. The one I used a few years back just had a direct connection to the battery from the panels, and switches for the lights. If there's actually a shunt controller in that box I'd be surprised.
RE: Relatively Easy Solar Power  
by K8QV on August 8, 2012 Mail this to a friend!
Harbor Freight seems to offer cheap Chinese imitations of real tools. You probably shouldn't assume the best. Just saying.
RE: Relatively Easy Solar Power  
by AF6AU on August 8, 2012 Mail this to a friend!
If you need enough amperes to charge up a depleted group 27 or 31 deep cycle in 1 day, you are going to need a lot more than harbor Freight's 45 watt 3 amp panels. Better off watching Craig's list, you can sometimes get used panels there for a good deal. I bought a 230 watt panel that had the connection box damaged for $100. It makes 36 volts (24V @ 9 amps,)or 18 volts unloaded (12V @ 18 amps) depending on how it's wired, so I feed it into a cobbled up 3x 2n3055 pass transistor + a lm317 regulator. Under full sun I can pull a constant 13 amps from it at 14 volts. Harbor Freight's panels are okay for a beginner, but costly. If you are resourcful (and cheap like me), you can find a lot more power for the buck, but you may have to cobble up a controller, or regulator, but you will have enogh power to fully recharge a group 31 deep cycle in 1 full sunny day.
Relatively Easy Solar Power  
by N3LKA on August 9, 2012 Mail this to a friend!
I built my own panels. I was fortunate to come across some laminated tempered glass for really cheap. I can fit 40 cells on each panel. I'm in the process of building another one. I use a morning star controller with 2 deep cycle AGM batteries.

The setup is used for when we lose power and we need light and a tv to watch. I use a small 600w peak inverter for the tv and 12V fluorescent drop light for lanterns.

I know I could could improve it a bit, but it works for what I need.
Relatively Easy Solar Power  
by TTOMAS59 on August 10, 2012 Mail this to a friend!
I would be interested in a solar panel for qrp (5 watt) operation. Can anyone recommend materials for this set up?

Thanks, Tim
Relatively Easy Solar Power  
by KD4LLA on August 11, 2012 Mail this to a friend!
My experience w/ a 60 watt panel, 10 amp charge controller and whatever sun is available is that the output is about 3 amps/hr. Just think of how long it takes to charge a battery @3amps...

Batteries are the weak point.
RE: Relatively Easy Solar Power  
by AF6AU on August 13, 2012 Mail this to a friend!
That would be easy, but there's more info needed... What voltage you need?
How long will you opeate? Day only, or night too?
Any accessories (lights?, keyer?)?

It's best to go with a panel, charge controller, and a battery, all matched for capacity. Then you have nightime ability, cloudy day charging, and power for lights and other things. If only a QRP rig, a 7 amp hour gel cell and a 15 watt charger panel would work great, and run the rig and a LED camp light longer than you could probably stay awake.


RE: Relatively Easy Solar Power  
by KI4TON on August 13, 2012 Mail this to a friend!
Not too sure about AGMs - they are too expensive for my budget - but definitely gel cells and even regular lead-acid batteries are damaged by overcharging. You can do some calculations to find the maximum safe unregulated panel for a given battery, but it isn't worth it. Panels and controllers are pretty cheap today.

I haven't checked prices in a while, but Arizona Wind and Sun (?) used to have better prices than most people. For larger purchases anyway.

The best way to charge a battery today is to get a Maximum Power Point Tracking controller and a panel rated at 18 or 24 volts. To charge a lead acid panel you need to raise the voltage to a pretty high level. MMPT controllers do this and manage the amperage, and also prevent overcharging on a sunny day. I have never been a fan of inverter/chargers. (One part will break, and you need to replace the whole thing) but they are getting better.

Batteries are expensive; take care of them.
RE: Relatively Easy Solar Power  
by VK3BFR on August 14, 2012 Mail this to a friend!
I run QRP from solar power and do it on the cheap. I have a 10watt panel (taken from an old electric fence system)connected to a 40AH gel cell (a reject from a UPS system)via a home made regulator. The regulator charges the battery up to 14v and switches off and waits for the voltage to drop to about 13v before switching on again. The system runs a Ten Tec 509 Argonaut, an FT817, an FT270 and occasionally an FT897. Sometimes the FT897 dies in the arse but not often.


Relatively Easy Solar Power  
by AG6IF on September 11, 2012 Mail this to a friend!
I have 2 similar batts in parallel, 80 watts in panels (20 20 40) hitting a charge controller, and everything wired into a rolling suitcase with power pole distribution.
My HF, APRS, and Echolink, rig(s) run off of this 24x7. I have a power supply wired into this as well, and using a lamp timer, it comes on a couple times during the night to top the batts a bit just in case of long qso's on echolink which eat more power when the transmitter is running... This Works great!
Panels are under $2 a watt now. Check my diagrams and pics on qrz under my callsign AG6IF. 73!
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