Well, after hazarding a huge snow storm and braving insane drivers to get the last parts I needed, I'm finished the power cable hack. The good news is - it's insanely easy to do. First - the usual warnings. This is not an HP approved or sanctioned project. While unlikely, it is possible that it could damage your dock or your Slate. As well, it will require you handling a soldering iron and a voltmeter. If you are not comfortable with this - do not attempt this project. Also, you will be sacrificing an HP Slate power supply. I recommend getting a spare one first. Using this cable might violate your warranty (although I'm not sure about that.. clearly it violates the warranty of the power supply you're about to hack up...). The project - to make a cable out of a spare HP Slate power supply that can be used with an external battery and with third party power supplies (like the ultra compact laptop/netbook power supplies). The parts: 1) Energizer "energi-to-go" or XPAL XP18000 battery. This runs around $150 and provides 3500mA output at up to 70WHrs. This is good enough to run a regular laptop for 6hrs (their claim) - so it should power the Slate for at least 9. With the 5hrs you get from the internal battery, you should see 11 - 15hrs of continuous use. Also, since the cable we're making matches the plug on the battery's charger, you can use the charger as a power supply for the Slate - eliminating an entire power supply, although the battery's charger at 3.45A is about 50% larger and heavier than the one that comes with the Slate. 2) A 2.5mm female barrel socket with plastic shell and strain relief. Mode Electronics 31-152-1 Should be available from any local electronics hobby shop, electronics parts shop or possibly from some Radio Shacks. 2a) A 2.5mm male barrel socket with plastic shell If you want to make a direct connect cable, you'll need this instead of the female socket. 3) If you don't have one - a soldering kit. 4) A pair of scissors, an exacto knife or similar blade. 5) A voltmeter. Now.. let's begin.