I am looking for the best way to implement a battery supply for my project. It needs to be able to fit in an enclosure measuring 5 x 2.5 x 2 inches. It needs to have a voltage in the range of 7 to 12 volts and have a fair amount of capacity. (maybe around 1500 - 5000 mAh?) The battery(s) also should be easy to charge, such as through a regulated voltage supply, with no complex control circuitry. It can be multiple batteries. I am mainly looking for the best type of battery here. (NiMH, SLA, Lithium, etc.) Any suggestions?