HVB Drain from 45% to 0% While Parked During Workday?

[murphy]

The contactors that activate the HVB are operated on 12 volts. If the 12 volt battery got low enough that the cars logic went nuts (technical term) anything is possible.

[lolder]

If the HVB contacts are closed and it is powering the car, the DC to DC converter keeps charging the LVB and system. When the HVB gets to it's emergency low shutoff point, the contacts open. The LVB powers the 12 vdc system until it dies.

[lolder]

I have had the low HVB three times in the last two years. The car will now not go as fast in EV and the display of available EV power is not as high as it once was. I believe the events are a cell permanently shorting. This doesn't change the total energy capacity much but it would lower the voltage and maximum power output capability. I usually have had a reconditioning event every 8000 miles but I haven't seen one since this started. Maybe once a cell shorts it is inhibited. I don't know what this bodes for the future. HVBs can tolerate shorted cells but not open ones as all the cells are in series. There are 204 cells in series so if 3 are shorted that's about a 1.5% voltage loss. Available power is related to the square of the voltage so peak power loss would be 6%. EV operation needs higher voltage the faster you go because of "back EMF" (voltage) of the motor so the maximum speed may be inhibited even more than the 6%.

Edited April 25, 2018 by lolder