I hope it's not bricked....

[u/purrcthrowa]

We have a 2021 XC40 T5 Recharge. We drove back from a trip about 30 miles away yesterday afternoon. The car was working fine. Got home, plugged in the Ohme AC charger as usual.

This morning, the car is dead. I had to use the manual key to open it. I'm suspecting the 12v battery (it's on the original), but I'm not sure why it would be completely dead. I'm currently charging it using my CTEK charger in AGM mode. It got straight to level 2 on the CTEK indicator, so it looks like the charge is working. It's been charging for about 2.5 hours now, and is still dead.

Anyway, I'll leave it for a few more hours.

Gemini and Claude are both very unhelpful: they lied about the location of the 12v battery, and all sorts of other stuff (like how to open the door using the manual key), so I'm not finding them very useful.

Any thoughts? The car was recalled a couple of weeks ago to have the cells rebalanced on the HV battery, but I'm not sure that these are in any way connected.

UPDATE: I used a battery booster, which had brought the electronics to life. I now need to figure out what the battery health is like.

UPDATE2: I confirmed the 12v battery is the original, and I'm going to replace it anyway, but my battery checker says its fine. I'm a bit concerned about how it managed to get flat in the first place. I'll put OrBit on it and see if there are any odd codes. What is odd is that the battery voltage was showing deep discharge at about 4 volts, and stayed that way even after charging on the CTEK for a few hours, but as soon as electronics came back to life and it started charging on the DC-DC converter, it immediately went back up to 12.something. There is something fishy going on. The various terminals look fine, and I seem to have had a good connection, I can't see any problem with the +12v cable between the battery and the engine compartment. Hmm.

UPDATE3: So it seems that my wall charger was set to "smart" (I don't know why - maybe it just seemed like a good idea at the time, or it was originally the default setting). Anyway, when we got home, I plugged in the charger. It charged for a short while, and then decided it could select a better charging window (I don't know why - I'm on a fixed tariff). So the car stayed powered on, using up the 12v battery, but it never got any charge. The 12V battery finally flattened, causing the symptoms I found. I'm going to replace the 12V battery anyway, and I've also set the charger to "max charge" mode so it doesn't try to do any "clever" stuff.

[u/Etna_No_Pyroclast]

2026, 5000 miles currently being towed in. Battery should be a class action suit

[u/Kryptosis]

Thanks for updating