Does anybody know for sure if the HCH will continue to run without the main pack? Will IMA still charge the 12V batt with the main pack out of the circuit?

Errmm... why would you even want to do this? The onboard computer will almost certainly start throwing IMA warnings at you, accelleration will be worse than a constipated hippo, and your mpg will suffer as well.

Someday I might even beat that wascally kenny!

No whammies... no whammies... no whammies...

Supposedly, this is the primary difference between the Honda system and Toyota. Honda's cars can run without the IMA while Toyota won't.

Also, I am pretty sure the 12V is not in the loop for regen. It's just a regular 12V battery like in any other car. I think it's used as a backup for the main battery pack to get the engine started in case the battery pack fails.

Support the Troops - Drive a Hybrid!

Yeup... the HCH is designed to keep going on a total failure of main pack.

My understanding:

REMOVING the 144V battery will prevent the car from running. A DEAD 144V pack will not.

The car will run if the 144V battery is dead, but it needs to be in the circuit and capable of at least conducting current through it (a dead battery still conducts; it just doesn't store), to get from the IMA to the 12V.

The main battery needs to be electrically connected. Energy flows from the IMA to the main battery, and the main battery is DC-DC converted to recharge the 12V. Since there is no alternator, there is no way to recharge the 12v if the 144V is not present. Unless you jumper and do some voltage&current regulation off the IMA directly.