Navigation Power usage

Has anyone got the numbers for the power draw for the navigation system handy? It becomes annoying to have to redo the un-lockout every time I restart the car, so I've been wondering if I can't make a way for the nav to have power more of the time. What I'm envisioning, is a secondary, small 12-volt battery mounted, probably in the center console, so that it recieves power from the car's system when the car is on, then delivers power to the nav when the car is off. I wouldn't expect it to survive an overnight power-down, but for running into a store, it seems plausible. Secondly, can the nav tolerate having the rest of the car shut down around it while it stays active?

 

<div class='quotetop'>QUOTE(aaf709 @ Jun 30 2007, 06:06 PM) [snapback]470739[/snapback]</div>

'Cause the Coastal Kit is $99 plus shipping, while a small 12V battery and some wire is about $20. Plus, there's the desire to do it myself, which always feels better then getting a kit to do something.