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I have a gadget that uses the Maxim <a
href="http://datasheets.maximintegrated.com/en/ds/DS3231-DS3231S.pdf">DS3231SN#</a>
RTC chip and it's been on battery backup for five months in a room
where the temperature has varied by 10-20 degrees F throughout the
fall and winter. I just started it up and the clock has drifted
about one second in that time. I say "about" because one second is
at the limit of what I can detect by comparing it to another clock
set as close to current UTC as possible. So it might be off by 1.99
seconds. In any case this is adequate for me. :-)<br>
<br>
This chip is only available in an SOIC-16 package, but it's not hard
to solder and Adafruit sells <a
href="http://www.adafruit.com/products/1207">breakout boards</a>
that allow using it with a breadboard.<br>
<br>
-Pete<br>
<br>
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