Had my neighbour drive it to --.-- km.
Very tiny bit left on the battery symbol.
Crawled out of bed to measure with a dizzy head.
Watchdog reads with handbrake pulled and selector in D and head lights on: 3.825V
Cell difference is 0.011 and NOT 0.005, so I wonder if the BMU and ECU are 'arguing' about that?
According to the display from 29Ah there is 8.4Ah or 29% left.
...but at that voltage I should have around 60% left.
Pulled the 12V.
After that I also pressed the START button for 20 seconds, just had a hunch. We do that to clear RAM in MacBooks and some other laptops 
I read somewhere that by disconnecting the 12V for a longer time the 15l petrol per 3 month counter gets reset !
So it is now obvious to me that the ECU has a volatile memory section that can be cleared too, by removing the 12V.
This might be the reason why it might not work with newer models as they changed something in the ECU to make the stored values resident.
This could simply be a matter of a software change to write the values in the resident EEPROM rather than the volatile SRAM.
Compared to the ECU the BMU would be a relative dumb device where you can't simply change it's Firmware.
I probably can only keep it disconnected for 5 hours before I will have to sleep and put the charger on overnight. Tomorrow at 12 noon I will know more.
