I go camping a lot and sometimes get worried about a dead battery (had it happen a few times). I have seen these 5600mah to 10,000mah power banks on Amazon pretty cheap,looking at a 5600mah PowerBank brand for 12.99 + 4.99 shipping, 5600mah UniCharge for 19.99 + 4.84 shipping or 10,000 RavPower for 19.99 and free shipping. Any ideas on these? If the PowerBank is OK, might get 2 of them. For a DIY, I have a few 7.4v and one 11.1v 5000mah Lithiums for RC car, I thought about getting a USB car charger and hooking it up to one one them and using it. I also have a couple NiMH batteries also. Any ideas on whether that will work or a bad idea?