I have a 2018 Soul EV and it has a very intermittent problem that seems to be getting worse. Sometimes we will shut the car off to go into a store — maybe only 15 or 20 minutes — and when we come back, the 12V battery is dead. It has passed a load test with flying colors, and most of the time there is no problem. We have been very careful to be sure we are shutting down properly, not in accessory mode,
When it goes dead, I can put a voltmeter on it and I’ll get between 3 and 8 volts — clearly dead. I can easily get the car restarted with a small battery pack, and be on my merry way. Once started, it will recharge from the main battery, or I can recharge it by plugging in.
But the other day, it wouldn’t start after a brief trip to the grocery store. I jumped it, but when I got home (15 minute drive) the 12V was still dead — not even enough juice to open the charging door. When I put an amprobe around the battery cables before plugging in, it read 3A discharge rate.
Perhaps there is a relay somewhere that occasionally doesn’t make the connection between the batteries? When you are plugged in, does the 12V charge thru the main battery, or charge directly through the on board charger?
The 3A discharge rate would seem to indicate that something is still on, even with the 12V dead. I can’t hear anything running, and I thought everything except the propulsion motor ran on 12 volts. Can the DC-DC converter run in both directions, discharging the 12V into the main battery? Seems unlikely, but I can’t think where that juice is going.