consumer and otherwise electronics questions

[Antti.Roppola at brs.gov.au]

> thanks to a very kind person on this list, i now have an old laptop to
> mount in my car for the mp3 player i'm building. you can see a bit
> about it here: http://repose.cx/tech/muse
> 
> i've a couple of questions i was hoping some of the people here might
> know, as electronics isn't my forte:

Here's a fairly involved description of such a setup, including stuff
on power supply:
 http://www.chaos.org.uk/~altman/mp3mobile/

> * i'm also on the look-out for a laptop battery for an IBM thinkpad.
>   is there a way to determine if the notebook is running off 'mains'?
>   this would allow my laptop to shut down properly when power is cut. 

Well the LCD changes when you plug it in, so it knows. Don't think all
Thinkpad batteries are the same though, and most old laptop batteries
seem to be dead most of the time. I am looking for a source of cells I
can use the re-pack the battery for my Compaq 486. If you don't mind
having them seperate, an ordinary Nicad battery shoudl be OK (they won't
run the laptop as long, but if it's only to put the laptop into
hibernation *shrug*)

Antti