When I turned on my Soul EV this morning, there was a large 'battery voltage' error displayed on the dash screen. The battery pack had about 85% charge, so I tried to drive the car anyway. I immediately noticed that it would not exceed 30mph/50kph so I turned around, parked the car, plugged it into our L2 charger, then took my wife's car to work. I wish I had thought to take a photo of the error message, but I was late for work and in a hurry.
I hoped that plugging in would charge the 12V battery, but no such luck. My wife called a few hours later in a panic - she said that she had tried to drive the car, but the dash was flickering on and off and the car would not move.
Disconnecting the lead-acid battery and charging it via a standard 12V automotive trickle charger seems to have resolved the issue, but it's still a little irritating that I could have been stranded. And that the low voltage dc-dc converter may not be functioning properly.