It often seems that backup batteries are device specific, so you’ll need to buy – and carry – a one for each of your devices. The goBAT II Portable Charger and External Battery from Scosche can charge most any USB-chargeable device. It has a 5000mAh lithium ion battery that can charge up to two devices at once. It has two USB charging ports – one 1A and one 2.1A. The 2.1A port can charge either the iPad or the Samsung Galaxy Tab. The goBAT II has enough reserve power to recharge an iPhone 3G up to 3.3 times, iPhone 3GS up to 3 times, iPhone 4S up to 2.6 times or to charge an iPad up to 55%. The goBAT II comes with a microUSB cable for charging; you use your device’s USB cables for charging them. The Scosche goBAT II is $79.99 at Scosche.