[pen_sq]

I'm not interested enough to drain my Kindle battery playing music, but I imagine they didn't expand the battery size at all. Battery lifetime gains were done purely in efficiency improvements. They probably have newer chip designs that are even more keyed in to powering off quickly, while still reliably detecting events where they're needed on again. The same old life on speakers (sluurp), 4 hours IIRC.

To go a bit off topic - Power is one good reason to leave out an SD card. The cheapest card on the block probably skipped on doing power management, and dumps any sleep command in the same bit bucket as error correction data. I'm not an EE, but power-down costs another separate power transistor (plus buffer transistors - data lines hate being fiddled while the lights are out), which eats their razor margins. So I've been told. At any rate, it's not worth trusting your hardware's stability and reputation to some moron at B-Data storage chips (available in flash and kettle cooked; our BGA goes great with DIP!).