REX little mistery

[tjburbach]

Glad to hear that your problem has been resolved. It is odd to think it all came down to the 12V battery. You would expect that the DC regulator responsible for powering the 12V system should provide plenty of power for the car regardless of the battery condition. This makes me wonder if the root cause of the issue was some kind of test/check the car does while shut down which was failing (or giving an abnormal value) due to low battery voltage. I know the car monitors the gas tank pressure as it cools down checking for any leaks, I wonder what other kind of system checks are down while the high voltage battery is disconnected.

Anyway, glad everything is working!
-Tim

 

[alohart]

It is odd to think it all came down to the 12V battery. You would expect that the DC regulator responsible for powering the 12V system should provide plenty of power for the car regardless of the battery condition.

The DC-DC converter that connects the battery pack to the 12 V battery for charging isn't always on and should not be. It is a 12 V device that requires a minimum voltage to turn on. If the 12 V battery is incapable of providing that minimum voltage, the DC-DC converter can't turn on to charge the 12 V battery. Sort of a Catch-22.

 

[jadnashuanh]

FWIW, there's a bypass circuit for the 12vdc battery IF the car is plugged in. If the battery is too low to start the normal computers, there's one that ends up being powered by the incoming acv that will slowly charge the 12vdc battery until it has enough juice to run things 'normally'. If the battery is too weak, that may never achieve the needed voltage level. This is what I remember from reading one of the i3 training presentations, that was awhile ago, so I may be off a bit.

 

[brubix]

The DC-DC converter that connects the battery pack to the 12 V battery for charging isn't always on and should not be. It is a 12 V device that requires a minimum voltage to turn on. If the 12 V battery is incapable of providing that minimum voltage, the DC-DC converter can't turn on to charge the 12 V battery. Sort of a Catch-22.

This explains why I was stuck even if I had 4% residual charge.