[itsbmw]

Hello,

Got a BMW X3 G01 30e 2021 (pre facelift)

The charging terminals under the bonnet were showing 3.6v.
I left the cTek charger on for 6 hours in AGM mode, after which I took off the charger to check the voltage which showed 8.5v but then dropped to 4.8 in 5 minutes.

Is this indicative of a dead battery? Or do I need to keep it charging for longer?

I was hoping to take 2 of the AGM batteries out to charge directly, but I must disable the high-voltage system (HVS) first.
I did unlock the high voltage plug, but am unable to enter PAD mode because the battery is so dead.
If I connect a Jump pack and try to enter Pad mode, it does not say that the HVS is disabled, I assume it might be because I am using a Jump pack?
I do have other faults in the car as it is being repaired one of them is about the High Voltage system ( safe to continue driving) that was also there before the HVS was disconnected.

Is there a way to check if HVS is disabled using ISTA?

* I was able to start the car a week ago with a jump pack and have it running for about 5 minutes, but after turning the car off the battery was dead again.

If the battery/batteries? end up dead, will it most likely be both the 12v batteries that need to be replaced?

[glennbk]

do you have BimmerLink by chance? The car is 3 years old. I remember the days when batteries last 5 years. These days it's a crap shoot. as for both batteries needing replacement...usually one goes and the other is following in short order.

[bouchy]

Main battery is probably gone. Very little chance that there's problem with cables from rear to front terminals. Measure battery voltage directly in the rear. When main battery is changed, then measure the auxiliary battery in the front. Disconnect main battery first.

Using few watts of ballast is the best idea. Suddenly, "12.1" V might change to e.g. 6V.