goldbrick wrote: ↑Thu Aug 29, 2019 3:42 pm^^Both good points but I still claim the required electronics are all there and only firmware changes would be required.
For example, disconnect the 12V battery from the DC-DC converter for some period of time and apply a load to it and measure the voltage or voltage drop or something similar. Finding a sufficient load to use for this test might be an issue with the existing wiring but I can't imagine the electronics on a Leaf are not sensitive enough to detect a dead or dying 12V battery. I'm betting it just never occurred to Nissan product development that it would be a useful feature to have.
If nothing else, measure the 12V level while starting the car and watch the droop. If it gets close to the point where other electronics will no longer work correctly due to low 12V power display an intelligent trouble code to warn the owner before it stops working completely.