They hardly work, just get a power bar like this http://www.amazon.com/Jackery-Fast-charging-Aluminum-Portable-Capacity/dp/B00DTXA578/ref=sr_1_1?ie=UTF8&qid=1396564353&sr=8-1&keywords=charging+bar and charge it when you go into town.

There are better ones out there but shopping is different for me because i'm in canada