I have been looking around for something to use as an UPS for my Raspberry Pi. I bought an Energizer XP8000 power supply weight 7.9 oz 4.3"l x 2.9"w x 0.9"h. It has an internal 5 volt 8000mah battery that has three outputs.
5 volts 1000 mA used for Raspberry Pi
12 volts 2000 mA
and 19 volts 2000 mA used for my laptop.
The XP8000 can be charged while using all three outputs. I currently am on six and a half hours of being unplugged from the 110 wall charger. The blue meter on the XP8000 has not even moved. By calculation I should get around 18 hours as the Pi uses .44 mAh.