I would get a good battery it should last a long time, I would not worry about it for at least a few months. Solar batteries need sunlight if it snows the array could be covered if you put it on your package tray it also could get covered up to get 1.2 amps the panel is 39x14xx1.2 and is $159
a 135ma (a tenth of an amp) 15x5x.75 $35
Did you know MB roadside assistance comes out free for life if you need a jump,or sell you a battery with install for about $150