On Monday, August 10, 2015 at 12:37:22 AM UTC-4, wrote:
I bought one of the solar chargers they sell at Harbor Freight for
around $20. They are made to charge a 12 volt battery at 1.5 watts.
Granted that is not a lot of power, but just to keep a battery topped
off, it worked fine.

I particularly bought it to keep a car battery charged for a battery
powered electric fencer, but I also took it when I went camping, so keep
my car battery charged after running my laptop computer off the car's
battery without starting the car to recharge the battery. The computer
often ran for several hours to play movies.

Anyhow, aside from the fact that it's cheap Harbor Freight junk.

That is likely the essential issue. You could look for bad solder
joints, an obviously defective component, then start debugging it
like any other electronic circuit. I bought a cheap VOM from HF,
not expecting much either. In less than a year, the voltage readings
went to off by 30%+. I think electronics are probably something to
be very wary of at HF.