I have the Battery Life+ Solar2 http://batterylife.com/chargers/blsolar2/
And it has safety features built into it such as Short circuit, open circuit, overheat & overcurrent. The instructions also say.
Now that said, this 2.5w charger is rated at a constant charging rate of 180mA (.18A) and cannot maintain my Pathfinders battery for more than a week. But take into account where I live and that I do have items that constantly draw of the main battery, and know it. Having this one, I now wish I had opted for the 5w, 410mA (.41A) version, in hopes that it would extend the time a bit more. Solar chargers with such low ratings are not meant to maintain a battery that has a constant draw nor are they really meant to power devices. They are simply meant to maintain a battery in a vehicle that is not frequently run.