One of the best places would be the starter relay for + and ground wire to the starter for - . The relay is under the black cover behind the petcock. You said "without removing the plastic" but this one is a single screw.
You can check battery voltage there with the engine running or off. There are many other places to check voltage but being smaller wires they'll have lower voltage if they're carrying any current.
The fan does use current when the bike is off, but only as long as the fan runs. When the switch at the bottom of the radiator turns off the fan, there should be zero current draw.
Last edited by Grinnin; 08-11-2015 at 04:47 AM.