I'm the original owner of a 2018. Never had any battery issues, but as most, got the multiple warning errors and charging issues within the first few months of buying it. When they became available, I had the dealer install the two software updates. Zero issues since then until this morning. When I started the car today, I noticed I left one of the map reading lights on, though my understanding is that the car turns them off when you lock the car. In any case, that's when the two errors showed up. Restarted the car (waiting until the display goes dark - remember this to overcome XM not working if you remote start the car) but they wouldn't go away. Drove away, and errors went away. SO... is it the 12v starting to go bad? Not too long ago I wanted to get it replaced at Sam's Club but they refused to do it as they don't change them on any hybrids or PHEVs. I guess I'll do it myself, but been waiting for a good day and would probably do it at Costco since it's closer than Sam's. I have a OBD reader that I periodically use to check the battery capacity (once a year). Can this also check to see if the battery is good or should I be better off stopping by an Autozone or somewhere to get the battery checked? Not due to visit dealer for another 3 months.. TIA.
Possible that it's a 12v battery issue. Check the terminals for corrosion. Depending on climate 12v batteries are only good for 4-5 years, generally. OBD reader will show the voltage of the 12v battery but not the capacity. If Autozone has a battery tester it would be worth a visit.
I can confirm that the "christmas tree lights" can be triggered by a 12V battery undervoltage, which usually results from draining the battery. Several of the lights do take a short drive cycle to reset, even after an OBD code clear. Recharging the battery can be done simply by engaging the DC-DC converter to send juice from the HV battery to the 12V, which can done by switching the car on. Plugging the car in will also engage the DC-DC converter and recharge the 12V, but the charge cycle won't start if the 12V is already too low when you plug it in. "Too low" is below 10.5V or so. The battery voltage should be ~11.2V when the car is off, and ~14.8V when the DC-DC converter is engaged and charging the battery. It is possible that the battery is aging -- mine is still the original 2018 factory one too, and is starting to show its age a bit -- but I just charged mine back up and the issue hasn't come back.
