[Pit Viper]

Timing on this threat is ironic. I had watched a video that showed that compartment empty and was using it for storage. I was rather surprised to open it and find a battery, especially after the dealer very clearly explaining the remote jump points since the battery is in the trunk.

[bavarianride]

I charged my 330i (dual storage) with CTEK US 4.3 this evening and it started at stage 3 and got to stage 8 in 3+ hours.

I first turned off the engine, and then closed the driver door and then reopened it. That sequence turned off iDrive (I guess that means ignition is also off).

I then popped the hood and connected CTEK to jump terminals(and the hood is left opened). The car did not make any noise at all.

[Emily172013]

I've been using a Battery Tender since I bought my 2020 M340i. Leave it overnight, hood open or closed. No problems, always fully charged in the morning.

[doublevanosrc]

I have the same options(along with a few more) and have the 2nd LG battery upfront. I wonder which options required the addition of another battery.

Originally Posted by NYC_340i

Was curios so I checked mine and I do have that second battery under the hood.

Sept 2019 build M340xi with the following options:

Premium pkg
Executive pkg
Driver's assistance pkg
Driver's assistance pro pkg
Remote Start
Harmon Kardon
Wireless charging

Now if someone has a similar build and doesn't have it the mystery just deepens lol