Time to start thinking about this again:
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I mounted the pack negative contactor this evening and wired it to the 12v keyswitch relay (recycled the fuel injection relay).
Man, is it ever LOUD when it pulls in. I mean
LOUD. Like...
!!CLACK!!
Now, I mounted it more or less on the passenger side shock tower, so it's telegraphing directly through the unibody, but still. I took it over to show Ivan, and it's got us reconsidering whether we should go ahead with the plan to put the other contactor on the go pedal to pull in/out pack +ve every time the pedal is pushed/released.
One of the joys of this little car is how utterly silent it is ghosting around at low speed. If the pack +ve pedal contactor can't be physically isolated to make it quiet, I definitely don't want it clacking away under the hood. It'll drive me nuts to have to listen to it every time I move my foot. The single keyswitch CLACK I can live with. It kind of adds drama to the "start up" process ... "Contact!"
The reason for the pedal-actuated contactor is: in case of controller failure, the driver's first instinct is to release the go pedal, theoretically cutting power pretty much instantly (assuming it doesn't weld). If we omit it, then a split second is lost, before jamming down the clutch pedal to mechanically shut things down.
Given that this is a low power machine, that split second is perhaps not an extreme problem. For someone with a lot more voltage & power in their pack, it's a problem.