Been through a lot, but it still pulls in the stations.
This one has a solar panel that never did work.

This article will show you how to power almost any radio with solar.


120studio.com
Copyright 2015.  All rights reserved.


Introduction

I've got a portable radio with a built-in solar panel.  That panel doesn't work.  I didn't want to throw away the radio, because it actually works pretty well otherwise.  The radio looks like it's been through the mill, but there are a lot of good things about it.

So I decided to fix the solar-panel situation, the right way.

As we'll see, it's pretty easy to rig up any radio to work with a solar panel.  Even on a cloudy day!



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In This Article

The Radio

The Solar Panel

Do This First

Another Test

Converting the Voltage


Conclusion



The Radio


The Kaito Voyager is one of those "emergency" radios that has the hand-crank, the flashlight, the blinking red LED's, and that sort of thing. 

These are great to have with all the severe weather we're getting nowadays. 

I liked the idea of a radio that didn't need batteries or wall power.  Sometimes you just want something that works during a power outage, even if you forgot to buy batteries lately.




An experimental antenna, shown here because I just like this picture.
Photo taken with a point-and-shoot digital camera.



I don't know if it's quite the perfect "emergency radio".  The crank on my Voyager broke off in about two seconds.  I had to use some real ingenuity to rig something that would not break off again.   I'm not saying the crank would break off for you, but this is a weak point they should improve.  

The radio was worth saving; it's got a dual-conversion tuner, and the dynamo mechanism itself is actually very good.  

One endearing thing about the KA500 is the circuitry.  It's all through-hole components;  no surface-mount stuff that I could see.  It looks like something you could actually repair, if you wanted to.  Even the circuit board material has that 1970's or 80's look.  Sweet.  I wish more radios were made like that today, even if this thing is kind of plasticky on the outside.

The radio has a built-in solar panel, which is probably inadequate even when it works.  The solar power on mine didn't work at all;  I'm guessing it was some fine wire trace, broken somewhere.  I didn't feel like taking or breaking the radio apart to get at it.

There had to be some other solution.  Maybe even one that would work for other radios!

Hey, actually... does that mean you could turn any radio into an "emergency radio"?

Well, you could solar-power just about any radio. Choose from a huge variety of portable radios; pick one that has a DC power input, and you can rig it for solar.

    


Solar Panel


We're going to get a solar panel that's made to charge a 12-volt car battery.  Or, at least maintain one.  These would work. They are about the minimum power rating that I would consider.  Better yet, get this panel.  Larger panels gather more light when it's cloudy, or when you have the panel placed less-than-ideally.

Got one of those panels?  Now we're going to use an adapter to bring the voltage down to whatever the radio needs.

Why do that?

If you ever want to use that panel to maintain a car battery, you'll have the ability.  It's a lot more versatile than a 5- or 6-volt panel.

You can power any radio with solar, as long as you know how to convert the voltage properly.  For now, let's assume we start with 18 volts DC or less.




Do This First


We're going to make sure the solar panel is OK.

Most of them have a diode to block reverse current.  Only the real junk ones would lack this;  they would drain your battery if you left them connected.

Be careful, though.  Quality Control will miss a bad one sometimes.  Once in a while you'll get a brand-name panel that lets reverse current flow.   Many people found out the hard way, when their nice new solar panel drained their battery within days.  

Even when the sun was out! 

That happened with a panel that I had, so I know it's a real possibility. 

Open up the back of the solar panel, removing any screws that hold it together.  Inside, look for a diode near the power cord jack. 

The cathode is marked by a silver band at one end of the diode.  This end should point toward the negative terminal, which would be the outer shroud on the power cord jack.   Conventional current flows from positive to negative.

If there's no diode, you'll have to install one.  If there is one, test it.  The diode could be present, but shorted.  This would allow reverse current to flow.  If you think that's happened, snip one lead of the diode, check with your DMM, and then resolder it.   Don't snip too close to the diode, or the soldering iron itself could kill the diode.  That could be what happened at the factory.  That, or static electricity.

If the diode is bad, replace it.

Mine has a 1N4001 diode.  That is more than sufficient for any panel that's only a few watts.   Basically, as long as it can handle currents of half an amp, and reverse voltages of 24 volts, it should work. 

If you want to waste less voltage, install a Schottky diode;  these have a low voltage-drop.  It's not required, though.



Another Test

Here's one more way to test the panel, if you want to get fancy.  Hook it up to the battery you want to charge, but put an ammeter in series. 

Make sure you hook it up right, so you know which way the current is flowing. 

If current flows back through the panel at any time, your panel needs the diode mod.  Don't think that just because your panel has an LED that it will block reverse current.  I had one that didn't.  It drained batteries, even when the sun was out.

Next, make sure you know what the voltage output of your panel actually is.  I don't mean the one published on the spec sheets.  Test it yourself.

Grab your handy-dandy voltmeter or DMM.   Take the solar panel outside.  Put the red lead of the multimeter to the positive output of the solar panel.  Put the black lead of the multimeter to the negative terminal of the solar panel.   If you have the battery clip adapter connected, it's easy:  red is positive, and black is negative.

Now, what's the voltage?  

If you're going to use a panel to charge a car battery, that voltage should be about 13.8 volts, give or take a couple tenths. Take note here, because the no-load voltage of the panel could be 18 volts. Under load, the voltage will drop. Read the manufacturer's instructions if you're not sure what it should be for your panel.

Trickle-charge panels don't even have their own charge controllers, usually.    They're just made so the voltage will drop to the desired level when they're connected to a battery.

In the next section we'll see how to deal with that.




With a couple of watts, you can power almost any portable radio.  This is a 2.5W panel, I believe.

I would recommend a five- or six-watt panel just to be sure.
It has more light-gathering ability, which is desirable.






Converting The Voltage


Some radios can run on 12 to 14 volts.  The Sangean WR-11 can do this.   A solar panel would let you enjoy all that retro-styled elegance in the outback, if you want.  Or you could listen to the radio out in the wastelands, post-Zombocalypse.  I don't know that the oldies station would still be broadcasting, but then again, if we let "everything is going digital" run its course, there won't be anything good left anyway. 

Many radios use 4.5, 6, 7.5, or 9 volts DC.  These are voltages you get from stacking standard 1.5-volt flashlight batteries. 

So, you'll need a step-down converter.

Get a couple of these right now.  They are so cheap, you might as well get five or ten of 'em.  Besides, what if one fails? 

While you're at it, pick up some 1N4001 diodes. I would just get an assortment; good to have for fixing other stuff.

Remember:  a useful solar panel should put out enough voltage to charge a car battery.  Just step it down with a converter to power a small radio.  Who cares if it wastes a little bit of power for that;  the radio will still play OK.

The ones with LED voltage readouts are nice, but mine doesn't have that.  You can just use a voltmeter to check the output.  I set mine to 5 volts, to power the Kaito.



The DC Converter

Notice the slots cut in the project enclosure.  This module can handle 4 to 24 volts DC input;  some can handle up to 30.
Set the output voltage, verify with a voltmeter, and you're all set.  Just make sure to put the lid back on.






The Adapter Plug

Best bet:  get a universal DC power plug set, like the kind they used to sell at Radio Shack.  You can still get them here.  Get the 4.5 or 6V power adapter for the KA500.

Figure out which plug fits the DC input of your radio. The Voyager KA500 takes an "M" sized tip, but I don't know if the KA600 does. 

Make sure you get the polarity right.  On the Radio Shack plugs, when you line up "+" with "TIP", that means the inside of the connector is positive.  This is what most gadgets use.  Lately I've encountered only one device that doesn't, but I'm sure there are others.

Another strategy is to collect wall-warts until you find one with the right size plug.  Snip the wires, use your DMM to determine which is which, and attach correctly to the DC converter.

I would recommend getting a 3" x 2" x 1" project enclosure.  Saw a slot in either end, where the lid meets the enclosure, so you can pass the wires out of it.  This will protect your DC converter.  Put the lid on.  Seal the holes up with silicone, against the unforeseen rainstorm.


                 


Conclusion

You can power almost any radio with a cheap solar panel.  Don't bother with 6-volt panels or whatever; get one that can charge a 12-volt battery, and step it down to the correct voltage.

This setup will power most AM / FM radios straight from the panel.  Even on a somewhat cloudy day. 

If you want to power your radio at night... that's yet another reason to get the right solar panel.  Use it to charge a car battery, and power your radio from that. 

I hope you enjoyed this article or found it useful.   The only way this site can exist is with your help, when you use the links on here to purchase your gear.  Your support is greatly appreciated.

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