this may be useful.

i killed the 12v battery in my 07 HCHII and it would not start. The IMA battery was nearly fully charged, but the car was not capable of starting. This would lead me to believe that the 12v system is isolated from the high voltage system entirely. This makes sense to me, you almost certainly cannot charge the high voltage pack through the 12v system.

I do have the technical manual and could track down all the wiring, but thats an awful lot of work.

on a side note, if nothing is using the power the cells are collecting then they will just sit there. meaning that if you put the solar cell out in the sun and there is nothing connected to it then it will just sit in the sun and get warm, which is precisely what they do when they are being used.

if you find a way to tap into the high voltage pack to charge it please let me know.