Tiny Solar Power for a Rainy Day

Tropical Storms in the Gulf, tornadoes in Alabama and lots of rain.

That’s not a time when you’d normally think solar power, except how little the panels are putting out. It IS a good time to hole up with a small project.

In the last post, I mentioned the Tiny Watts group and their tiny projects. And I mentioned that Solar George had given me an idea. I had a couple of small solar panels from garden lights. I found them in the dumpster at a house I was rebuilding, so free solar is always good. I think I may have another from a light I bought that didn’t last long. Anyway, these two put out about 6 volts in good sun. A load will drag them down to 5v, so that sounds good. I would guess they are in the 2 watt neighborhood, so that sounds tiny. Next, I scratched up a couple of micro-USB cords and cut off the big ends, leaving a few inches with which to work. I buy those by the sackful, because they get lost or messed up. No telling how many are stuck in the seats of my truck.

Strip back the wires on the big end of the USB cord and plug into a USB charging source to determine what wire does what. USB has 2 data wires and a shield in addition to the power wires. I guess right that red and black were the positive and negative, but don’t assume yours is the same as mine. Check the polarity. Toss the big end and strip back the insulation of the small end a bit. Leave enough room to get some shrink tube or tape on the joints when the soldering is done.

Cut off the connector on the panel and figure which wire does what. In my example, blue was negative and brown was positive. Your mileage may vary. Red to brown, black and blue is the order of the day.

Warm up the soldering iron and find the solder, shrink tube and/or tape. I slipped on small shrink tube over each conductor of one end and then a bigger, longer piece to cover the entire joint. I didn’t have any heat sealing marine shrink tube or I’d have used it to seal out water and make a better physical grip. Wrap and solder the joints, slip over the shrink tube and heat shrink it with the solder iron, a torch or a heat gun.

I plugged it into my Motorola flip phone, the only kind that works where I live, and it told me I was using an unauthorized charger. It is fussy that way. No problem on my LG. I plugged it into my Tomo 18650 battery bank and it went to charging, even with the heavy overcast. I can use the 18650 cells, recycled from the many laptops I have outlived, in my flashlight or charge two phones at once and I can charge them at night. My Motorola gets along with it. Since the battery bank has two USB ports, you can even plug your iPhone cord in. The microUSB with the solar panel is more useful, I think, because it plugs into more things and you may be able to still end up charging the iPhone.

Yes, I know you can buy a battery bank kit with built in solar charger and even an LED light for just a few bucks on eBay, and I may even get one, but this project was recycling some good junk box stuff and making something useful. The long wire on this version will let me stick the panel outside and keep the stuff getting charged inside out of the rain. Order one of the kits and build your own if you don’t have stuff in your junk box. Good fun on a rainy day.

Warning: Different phones react differently, so keep an eye on it. This is unregulated, so don’t wander off, leaving the phone plugged in to overcharge or damage the phone. A 12v panel wired to one of those cheap USB cigarette lighter adapters may be safer.

–Neal