[Beowulf] Mobo battery life in constantly on systems?

[Jim Lux]

At 04:14 PM 7/27/2007, David Mathog wrote:
>The question: what is the expected motherboard battery lifetime in
>systems that are continuously on?
>
>Background:
>
>The question arises because it was necesary to cycle the power today
>on a couple of nodes by unplugging them and then plugging them
>back in again.  When one came back up the BIOS settings were gone.
>That wasn't evident until a keyboard and monitor were plugged in.
>Losing BIOS settings when power is removed is pretty much the
>classic symptom of a dead motherboard battery.

battery life is pretty independent of power cycles. It's more 
sensitive to temperature than anything else (hot = shorter 
life).  The current draw is so small, you're essentially getting 
shelf life regardless.


>These nodes are now about 5 years old, and that is about the average
>battery lifetime in PCs that are turned off every night.  However these
>nodes have been on 99.99% of that time, so presumably the drain on the
>battery should have been nil.  Shelf life for motherboard batteries is
>typically about 10 years. There is no info on how old the batteries were
>that went into these systems, but presumably Tyan goes through a lot of
>batteries and these were probably fresh when installed.
>
>So bottom line, is this just a freak event or would you expect the
>other motherboard batteries to also die soon?

James Lux, P.E.
Spacecraft Radio Frequency Subsystems Group
Flight Communications Systems Section
Jet Propulsion Laboratory, Mail Stop 161-213
4800 Oak Grove Drive
Pasadena CA 91109
tel: (818)354-2075
fax: (818)393-6875