Well let me tell my little tale about solar electricity. I inherited a solar powered fence charger I set up a low strand to keep critters out of her tomatoes. I used it until we got busy with sports. Our kids, not us. So it sat in a leaky unheated shed. I set it out and got 8 volts when I put a meter to it. I let it go a few days and put the dead 6v 9ah battery back in it. I came back and the battery read 6.4 V. Pushed the on button and "CLICK"and the operating red light came on. 30 yrs old at least. Guess where it was made? The thing was all metal except for the panel. I'm guessing it has lost some power, but it works!
