You can buy a better charger (3-5 joule), a 5 watt HF panel and take a tired battery out of a car or tractor all for half what those POS cost. Got a whole pile of those all in ones and none work for very long. Dealer probably likes them because people have to keep buying new ones every year.

Buy a panel like this:

http://www.radioshack.com/product/index.jsp?productId=4218514&CAWELAID=515756387

Clamp it to your battery and clamp your charger to the battery and you are set.  You can even run the charger off just the panel in daylight hours.