Wall Plug to charge batteries

I have had 2 batteries plugged into a USB square that's plugged into a wall for over a week now and they still aren't fully charged....Is there a recommended power cube that works best with these USB cables that the batteries come with? I know some are lower power than others but this is really inconvenient to take this long. And I have solar panels on all of them but it's winter and we don't get enough sun.Also, any way to put TWO solar panels on one camera?? I have an extra panel....