You could try something like the Dallas DS1287 or 12887 (which have extra
built-in RAM) or the Motorola MC146818.  I know the Dallas parts have a
built-in battery and nonvolatile RAM (spec says it'll last for 10 years
without power), I'm not sure about the Motorola.  They're used in PCs for
configuration storage and RTC.

-----Original Message-----
From: Hickman, Aaron <HickmanAB@MAIL.VMI.EDU>
To: PICLIST@MITVMA.MIT.EDU <PICLIST@MITVMA.MIT.EDU>
Date: Thursday, August 05, 1999 12:20 PM
Subject: battery backup for RTC needed


To All,

        I am looking for a simple battery backup solution for a project
involving an RTC.  I would like to keep the clock running should power,
normally
derived from an AC to DC converter, be interrupted.  I have no experience in
battery charging/backup designs.  Could someone point me in the right
direction,
preferably towards a design available on the internet?

Sincerely,

Aaron Hickman