Tripping a relay.

    I'm constructing something similar those "solar lanterns" you see in 
people's gardens, except on a larger scale.  It charges up during the 
day, and automatically turns on at night.  I'll be using a photvoltaic 
panel to charge a 12v 12Ah battery. The battery will be driving, through 
a driver of course, about 90 feet of ELWire. Basically what I want to do 
is just use the light sensor and the RCX to detect when the sun has gone 
down and send its 9v signal to a relay, to let the juice flow from the 
battery to the EL driver.  My question is about the naming of relays. If 
the relay is labeled at 9V, does that mean it takes 9V to trip it? How 
is the load that the relay is capable of sustaining denoted. Basically I 
need 9v in and it has to only turn on 12V. Anybody got a favorite relay 
they like? If I get a relay that's rated well above the voltage and amp 
load that I need, will it still work? Thanks.

-- 
Dan Novy
Technical Supervisor
Flash Film Works