I'd just turned On the air conditioning loading the 12V system down below 10 - ah ha, my 12V battery must not be making good connection! My DC-DC converter can not run so many accessories alone..
I rolled a window down and made a smooth recovery with minimal honking behind.
Back home I confirmed my theory and began to clean the 12V battery connection. With the 12V battery cable in my left hand furiously working it with a wire brush it slipped falling upon the high voltage battery. Zap!
Bitten by my minimalist exposed high voltage battery design!
1 motor controller logic board
12V to 5V USB converter
at least 1 cell monitoring board..
The damage was repaired by Manzanita Micro and we should be on the road tomorrow. :)