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Small PV Solar Cell Charger Questions Answered

I volunteer as a ski patroller at a ski resort in northern Vermont.  Like many other ski resorts, we monitor Family Radio Service (FRS) Channel 9-11 for skiers who might get lost or hurt within our resort's boundary or sometimes outside the resort boundaries.  Due to the FCC restriction that FRS channels are limited to only a half watt (0.5w) they have very limited range.  So in order to monitor channel 9-11 effectively, we keep FRS radios plugged in all over the mountain in all of our ski patrol huts where there are always patrollers on standby in case of injuries or lost skiers.  One of our huts does not have any electrical power, so we are constantly cycling freshly charged radios to and from that hut, almost every day.  It would be a lot less of a nuisance if we could charge that radio with solar power.  

On the wall outlet plug for charging station for the radios we use, the label says the power output from the ac/dc adapter says it outputs 9VAC 200mA.  I assume this means 9 volts alternating current at 200 milliAmps.  Could I simply find a PV solar cell that outputs 9 volts a/c and connect it to the wire that runs into the radio charger?  Most of the PV cells I found online have a watt rating, but I'm not sure if that matters or not.  Where is a good place to find a specific PV cell for this purpose, for reasonable price?

If anyone person in the Northeast is able to offer significant help for this, I could probably take care of one free lift ticket for your time and help.  I'm also posting an image of the wall outlet plug label and charging station.

Thanks, David


this plugged into a motorcycle battery would then charge the radio from a car type charger.

I'm lost.

If you let me know what batteries and how many the radio currently uses I'll draw you a little diagram tonight. Might make it clearer. It shouldn't be a hard project, I just didn't explain very well :)

PS: Later tonight after work, I can look at the NiMH batteries and tell you what the voltage and mAh ratings say, etc.

The radio's use either the rechargeable Nickel Metal Hydride (NiMH) battery pack that came with it, or they can use three AA batteries. The charging station will only charge the NiMH batteries that came with the radios.

I don't have the radios here in my office, but I'm 90% sure they are the same as the Motorola T9680 models that can be seen here:


If the link above doesn't work, try this one: http://tinyurl.com/t9680

Thanks, David

You wrote: Could I simply find a PV solar cell that outputs 9 volts a/c and connect it to the wire that runs into the radio charger?

As Jayefuu mentions, you only need to use a solar cell that puts out DC, however, hooking a cell (or bank of cells) up to the DC input to the battery directly will not help much. It will charge the battery, but at night, or when cloudy, it will DIScharge it also. You also need to put in a few "safety nets";  such as a diode to prevent discharge while "not" charging.   A small "over-charge" circuit would be advisable also.

Since the radio also works with batteries (DC) then after the 9VAC goes in then one assumed it's rectified. Since PV solar cells generate DC why not use them to charge a large external battery or similar then wire the external battery to the battery connectors within the radio?

This will save you converting the DC from the battery the solar cells feed into AC only to have the radio convert it back into DC.

What batteries and how many does the radio take normally?