I carry the following external battery pak when I know I may not being able to charge my phone for an extended period of time. Yes it is large 5.1 x 3.2 x 0.6 inches ; 5.3 ounces. But this allowed me to use my Evo yesterday for eight hours, this included two movies the internet and pandora net radio and was still nearly at full charge. I bought mine at target and I see amazon has them for $53.10 The following is from the amazon site Energizer XP4001 Power Pack. Dual USB outputs provide simultaneous charging of two devices or one device for twice as long. Perfect for two cell phones, two devices or two people! Up to 25 hours XTRA talk time or 120 hrs of XTRA music time. Share your power or double your power - either way it is twice as good! For more information go to www.poweryourGear.com. Also charges iPods, iPhones, cell phones, smart phones, GPS and more. Comes with 6 cell phone tips, 3 media tips, digital camera battery charging tip, AC adapter and carrying case. Product comes with FREE TIPS FOR LIFE on our website at XPAL Power.