Here's my system for emergency electricity during winter, when the sun is too low to give the solar panels any oomph. I carry some largish, rechargeable 12 v 7,2 ah batteries to the office, and charge them there (above). At the cabin, I hook them up to whatever needs some power, like a lamp (below). Most everything I have is fitted with a cigarette lighter-type outlet.
Below is another option, the "BattPak". Stick some AA-cells into it, and a cigarette lighter-style plug, and you're good to go. Works fine with that spawn of Satan, the cell phone, not so good for a laptop.