I know the stancor 120-901 relay is popular among listmembers for
dual-battery setups, so I ordered one when I was preparing to do my big
electrical project.

I finally got around to looking at the detailed spec sheet, and see that the
relay is rated for 12v of coil voltage, and is suited to take up to 10% more
than that.  (The spec sheet is here:
http://www.stancor.com/wrdstc/pdfs/Catalog_2006/Pg_052_53.pdf).   Of course,
10% more than that is just 13.2 volts, which is below what you'll see in
your van when driving around.  In fact, at the bottom of the spec sheet,
Stancor has printed the warning:
"Note: Caution must be used in coil selection for use in 12 volt systems
where battery charging may expose coil to continuous, higher-than-rated
voltage. Stancor will not be responsible for consequences of misapplied
solenoids."

So, is this relay not such a good choice after all?

On the other hand, it seems they have another relay (120-914) intended for
automotive use and rated up to 15volts (its on the same spec sheet).  If I
read the spec sheet, this will come online at 11.25 volts (75% of 15), which
should be fine.  Maybe this is an acceptable choice?

Thoughts?
-Wes