Just be careful though. Like anything in the world, even Kensington Power Pack battery also sometimes goes bad, stop working suddenly. I wouldn't count on as a sole source of power.
Having said so, it's more likely that your USB pass-through is going to break before Kensington - as these USB pass-throughs are poorly built - so just be sure not to yank the wires, nor twist it. I normally only use when I'm home, watching TV or surfing the internet. I also took it out few times - but it's little cumbersome to have some wire and I look like I'm sucking something inside of my pocket. I can't care less on how I'd look, but I'm more conscious that my USB pass-through would break. So when I'm at work or on the run - I've been just using my batteries - and when I'm home, I start charging all the batteries and just stick to the USB.
I found on my 801, original battery performance isn't really that bad, but on my mini RN4081... OMG, what a difference Kensington makes.
