35W is a huge amount to leave running in a car.  The blinking LED on a car 
alarm consume maybe maybe as little as 5 milliamps considering the duty 
cycle.  

When building a car computer, there are ways to get the OS and applications to 
load fast.   Perhaps you don't need to leave the power on?

If you really need the thing to run unattended, perhaps for remote access of 
some kind, you might need to look at non-standard CPUs and use only an unlit 
b/w LCD.  

Jeremy

On Thursday 01 February 2007 12:12 pm, Donovan Niesen wrote:
> I'm considering a project that would involve connecting a very
> low-power Computer on Module and an LCD display inside a vehicle.  The
> vehicle will not be driven or possibly even started for an entire week
> so what I'm wondering is if anyone knows how long I might have on a
> fairly standard car battery if I'm using ~35 Watts from the LCD and
> the CoM?
>
> My goal is a full 7 days so if I need to use a lower power LCD so be
> it.  Otherwise I will need to find a different way to power the
> device.
>
> And yes, the CoM will be running Linux.