🚀 go-pugleaf

I would like to run a small computer on a car battery.  Low power drain is
a must, since it will be running constantly.  Here is approximately what
I will be wanting to power:

   80c286 1/3rd size board, running at about 4 MHz
   Some Alpha A-BUS cards for D/A, A/D, and digital in/outputs.
   A solid state SRAM disk drive, about 256k-384k, with its own battery.

The system will be able to monitor its battery life and shut itself
completely off to prevent excessive battery drain, but my goal is for
at least 2 days of operation without charging.

Question 1: How can I power the motherboard?  I am interested mostly in
efficency.  Would 5V regulator ICs do the job as well as anything?  I
assume most motherboards don't use -5 or -12 volts...  The A-Bus cards
themselves simply require any unregulated 12V source.

Question 2: How much battery life could I expect?  I have never seen
car batteries with amphour capacities stated; just their maximum
cranking amps.  I assume more cranking amps means a greater Ah capacity,
but this does not necessarily indicate a predictable relationship
between the two.  A dual battery isolator will be used to provide a
battery just for this job, however...  Probably the best die-hard I can
afford.

Thanks a million for any responses...

-- 
Jeff Noxon
jeffn@nuchat.sccsi.com
713/721-6820 CDT Houston TX