Just to update... I've using my external batery pack almost everyday since last week and it's been working really well. I was worried that I might have to solder in a diode to prevent electricity from flowing back to the external battery pack, but that's not the case. With fully charged external batteries, my N800 sees it as primary source of power and it keeps the internal battery charged. Even with all the re-boots (I was cloning os to sd cards), I was able to work three full days. This is while listening to fm/internet radio, surfing the interweb, watching Matrix and the Fellowship of the Ring, almost constant usage throughout. I don't have to worry about battery running out. I love the flexibility the external battery pack offers me.