Picked up my new Jazz yesterday, and as we are low milleage long holiday people, it was one of my handover questions.
It will not start if the reduced size 12V battery is flat- it is for activation..
It can started by another car as normal.
It can be charged by a intelligent battery charger without being disconnected from the vehicle.
Although I don't know the exact arrangement for charging it when it's running, but the manual (p72) shows an icon that displays when it isn't charging. If it comes on while driving and you need to stop DONT turn the engine off it might not start.
Now p227 says don't let the high voltage battery get close to zero or it won't start.
I have been told that the high voltage battery can/will charge the 12V one.
But having only just taken the car from the dealer the hybrid battery indicated half charge and the short journey home and then supermarket reduced it to 3/4 bars.
During the second trip I selected the power train to display but on such a short journey was unable to get any meaningful info.
But the dealer said if it fails to start use the roadside assistance provided by Honda.
.