A few updates to report:
The substation that is all of the gear necessary to isolate my pack has been improved again. I noticed with my original ideas that the discharge resistor which was across the main (ipso-facto, half) pack contactor meant that the two half packs were actually no longer isolated! Bit of an oversight, but rather than come up with a new and more complicated means to switch the HV relay, I decided I would just use a fourth contactor as the main isolation. This means there needs to be a sizeable switch yard on the outside of the pack. Altronics sells these clear faced ABS boxes which are just the right size that it won't be in the way of your balls on the bike, yet clears the lower part of the main frame of the bike.
There's enough room to bring all of the charge leads, 12 V leads, auxiliary contact leads and the main high voltage leads outside the main battery box and down into this main control box. I can put the relay logic for switching all of the contactors in here too. It's still tight, but flows much more logically. There's room for a 75 mV, 500 A shunt as well. The voltmeter would be able to go across the main outputs too, but isolation is going to be a big of a headache. So here is what should be close to the final high voltage wiring diagram:
Needless to say, all high voltage wiring will be kept inside conduits wherever possible. All of the low voltage wiring will be inside that soft insulation material to stop it from rubbing through anything.
So here's the logic:
With the key off and the bike parked, nothing is closed. All contactors and the HV relay are not energised. The discharge resistor is across the controller, which is isolated from the battery by the main contactor and the precharge circuit is open too.
Turning the key on energises the quarter pack contactors, the half pack contactors and the HV relay - opening the discharge circuit, and closing the precharge circuit. Some seconds later, the delay circuit allows current to flow into the main contactor coil, closing it too. The bike is now ready to ride.
Turning the key off de-energises all of the contactors and the HV relay, returning it to the normal controller discharge state.
Plugging in the charge leads causes the charge enable relay to energise, illuminating the charge LED and closing the quarter pack contactors, but keeps the half pack, main, and HV relay de-energised. This is so I can charge both half-packs at 350 V. It also means the bike cannot be ridden away, even if you turn the key on.
Make sense?