[Bkkee]

Hi,

Sorry if it’sa long post as in trying to provide all relevant information, will appreciate some advice. My MY 2021 X7 was in for repairs for about 5 months during which time the car was mostly switched off and not driven more than 100miles. I received the car over a month ago and today (after driving it for about 600 miles getting the car back last month) it suddenly won’t start, the battery went fully dead to extent that no lights would turn on and the car won’t even lock/unlock. No error messages on dashboard prior to this issue. Tried jump starting it but it didn’t work. Called in roadside assistance, their 12v battery charger didn’t work either (only managed to turn on the interior lights) so tried with 24v charger, initially it didn’t work either but trying several times and alternating between 12v and 24v (24v to turn on the engine and then promptly changing back to 12v to keep the battery charging) it cranked the engine on. Kept the charger connected to charge the battery for about 10 mins when I noticed the error on iDrive screen that read “ Stop carefully. Do not continue driving. Failure of safety-relevant functions if you continue driving. Battery can no longer be charged. Please call roadside assistance.”. Roadside assistance guys suggested I go on a short test drive, after driving half a mile or so the car went into limp mode, first force changing to neutral gear, then dashboard lights and headlamp turning off and a few seconds later the engine switching off. Luckily was a hundred or so meters away from home so close to roadside assistance guys so with the help of their charger I drove the car back to home (while their charger was still connected to my car).

I’m not sure if it’s worn battery or anything to do with alternator or even worse the 48v Li Ion battery? I’m also surprised at the sudden occurrence of this issue with no prior warnings.

One other point to add, I detailed the car today which took me several hours and during this time the car was unlocked (lights and speakers etc off). I also noticed the 48v battery under the hood was slightly wet from washing the car. I would assume it would be normal for the battery to get wet from washing etc. so this wouldn’t have caused the problem? If it is alternator would have I not received some errors in advance?

Some pictures of the errors/warnings attached. Any suggestions will be highly appreciated.

Thanks

[Orient330iNYC]

if the car was left for a few months with a low state of charge, the main agm battery might be damaged and the LI Ion is completely flat.
if the main battery's charge drops, the car will use the 48V battery to bring it up to the min level, then repeat until the 48V battery is dead.
if the charge in the li ion battery is completely flat, the battery might also need to be replaced (Li Ion batteries do not like to be drained completely and the battery protection circuit might have kicked in and bricked the battery).

i suspect at a min you need a new main agm and possibly the 48V battery( im not sure if the 2021 is a mild hybrid with a 48V li ion or if its got a 12V li ion)


you should NOT be applying 24V of power to the car, that will likely fry something,none of the systems are designed for 24V.

[Bkkee]

Originally Posted by Orient330iNYC

if the car was left for a few months with a low state of charge, the main agm battery might be damaged and the LI Ion is completely flat.
if the main battery's charge drops, the car will use the 48V battery to bring it up to the min level, then repeat until the 48V battery is dead.
if the charge in the li ion battery is completely flat, the battery might also need to be replaced (Li Ion batteries do not like to be drained completely and the battery protection circuit might have kicked in and bricked the battery).

i suspect at a min you need a new main agm and possibly the 48V battery( im not sure if the 2021 is a mild hybrid with a 48V li ion or if its got a 12V li ion)


you should NOT be applying 24V of power to the car, that will likely fry something,none of the systems are designed for 24V.

Thanks, appreciate it. You are right, I had checked it is indeed 48v Li Ion (Mild hybrid). The fact that the engine had started and managed to drive half a mile or so due to external charging, would it not suggest that battery is charging fine but alternator may not be able to charge hence why battery went dead in the middle of driving, am just thinking out loud but could be wrong. (Roadside assistance guys did mention the battery hadn’t charged from driving).

[Orient330iNYC]

No, driving a short distance wont appreciably charge a dead battery. You can charge both main agm and li ion with the following( from the terminals under the hood)

1) 12v charger of greater than 20A capacity
2) hood must remain open.

[Bkkee]

Originally Posted by Orient330iNYC

No, driving a short distance wont appreciably charge a dead battery. You can charge both main agm and li ion with the following( from the terminals under the hood)

1) 12v charger of greater than 20A capacity
2) hood must remain open.

Thanks for the clarification. I’ve ordered a 20A 12v charger, fingers crossed it will work. By the way how would I know if alternator is the problem? Would a warning pop up when taking the car out for drive after charging it?

[Orient330iNYC]

Originally Posted by Bkkee

Thanks for the clarification. I’ve ordered a 20A 12v charger, fingers crossed it will work. By the way how would I know if alternator is the problem? Would a warning pop up when taking the car out for drive after charging it?

i would go a little higher... 25 or 30A
the SIB on this lists:
Important: Trickle chargers (< 20-amp output) or solar chargers will not be able to charge the 48 V battery,
but could prevent further discharge to the 48 V battery when the 12 V battery is properly maintained to
optimal SOC.

im not sure if it wont charge the li ion at 20A, but at 25 you've exceeded the listed.

based on what you described, i suspect this is what happened:
48 V battery may become totally discharged, and possible replacement needed if:
a) The vehicle has been charged using a 12 V charger with the hood closed during a long stationary period,
the. For example, the showroom or storage.
b) Vehicles stored for an extended period connected to a low output solar or trickle charger.
c) Vehicles stored for an extended period with no charger connected and not properly maintained 12 V
battery.
Fault memory:
803419 - Batt48: Total discharge
803408 - Batt48: Emergency announcement: Cell voltage too low
803437 - Batt48: Cell defect - total discharge
Important: Trickle chargers (< 20-amp output) or solar chargers will not be able to charge the 48 V battery,
but could prevent further discharge to the 48 V battery when the 12 V battery is properly maintained to
optimal SOC.
CAUSE
a) The 48 V battery does NOT charge when using a 12 V battery charger with the hood closed.
When charging the vehicle using a 12 V battery charger, the 48 V battery is ONLY able to charge with
the hood open.
b) Trickle chargers and solar chargers may not be able to properly maintain the 48V battery.
c) Prolonged used of the “Emergency charging function” causes the 48 V battery to become totally
discharged. This occurs when the 12 V battery is not properly maintained and the SOC of the 12 V battery
drops below the critical threshold value while the vehicle is in sleep mode. The vehicle is woken up and
recharged from 48 V battery. If the 12 V battery is not properly, maintained this cycle repeats until both
batteries become totally discharged.

full sib here
https://static.nhtsa.gov/odi/tsbs/20...02468-9999.pdf

[Bkkee]

Originally Posted by Orient330iNYC

i would go a little higher... 25 or 30A
the SIB on this lists:
Important: Trickle chargers (< 20-amp output) or solar chargers will not be able to charge the 48 V battery,
but could prevent further discharge to the 48 V battery when the 12 V battery is properly maintained to
optimal SOC.

im not sure if it wont charge the li ion at 20A, but at 25 you've exceeded the listed.

Thanks, I ordered a 25A charger and started charging with hood open. Surprisingly enough the battery got fully charged within a minute or so but I still kept the charger plugged, after a few minutes a double thudding ”music” started coming from under the bonnet (from area between the engine and front grille) and indicator lights started blinking, I’ve attached a video (please ignore car alarm from another nearby vehicle), not sure to what make of this;

View post on imgur.com

[streborx]

OP -- was your 5 month repair episode done at a BMW dealer (where keeping the batteries charged should have been SOP), or at an indy shop? I agree with other comments -- if your batteries were severely depleted and charge cycled during the 5 months, the batteries might now be compromised. I'd have a dealer test both.

[Bkkee]

Originally Posted by streborx

OP -- was your 5 month repair episode done at a BMW dealer (where keeping the batteries charged should have been SOP), or at an indy shop? I agree with other comments -- if your batteries were severely depleted and charge cycled during the 5 months, the batteries might now be compromised. I'd have a dealer test both.

Thanks for your comment. It was actually at an Indy shop (who had it passed on to BMW for a month or so during that time). I’ve also had it at a BMW dealer a month ago for an unrelated work and they had it plugged in for charge overnight with bonnet open. I’m in touch with the garage to get the car seen, too curious as to what it will come out to be the culprit.

[Orient330iNYC]

Originally Posted by Bkkee

Thanks, I ordered a 25A charger and started charging with hood open. Surprisingly enough the battery got fully charged within a minute or so but I still kept the charger plugged, after a few minutes a double thudding ”music” started coming from under the bonnet (from area between the engine and front grille) and indicator lights started blinking, I’ve attached a video (please ignore car alarm from another nearby vehicle), not sure to what make of this;

View post on imgur.com

something isnt right. i suspect you have a bad battery- it shouldn't have gone to full charge that quickly.

if the tow people really applied 24V to the car something might have gotten fried.

at this point a workshop needs to read the codes and diagnose.

[Bkkee]

Originally Posted by Orient330iNYC

something isnt right. i suspect you have a bad battery- it shouldn't have gone to full charge that quickly.

if the tow people really applied 24V to the car something might have gotten fried.

at this point a workshop needs to read the codes and diagnose.

I gave it a try yesterday again and for some reason it started charging. Charged to about 13.2v and 86AH (it’s a 105AH battery), briefly disconnected charger for a few seconds and reconnected, for some reason amp dropped down to 0 again but voltage remained the same. Had a first try at ignition since charging this morning and it worked. With ignition on the voltage reads above 14.2v. However the orange engine check light is still on however no warning messages on iDrive or vehicle check settings. Guess engine light suggests battery still needs replaced.

[streborx]

Low battery voltage will begin throwing all kinds of DTCs along with the CEL. Have you used an OBD scanner to read out the codes and reset them?

[Bkkee]

Originally Posted by streborx

Low battery voltage will begin throwing all kinds of DTCs along with the CEL. Have you used an OBD scanner to read out the codes and reset them?

I actually took the car on 10 mile or so drive while having car connected to bimmerlink, the battery (12v AMG) charge level remained at 83% throughout the journey while the 48v battery dropped from 95% to around 50-60% most of the time and recovering back to 88% towards the end of the journey. Battery no doubt needs replaced but not sure of 48v should be replaced as well.

Bimmerlink identified almost 300 errors majority of them to do with low/high voltage, only under 10 or so “present/active” errors, the rest being “not present” or “from memory”.