[lmgee]

I have a 2021 330i xDrive. I noticed there appears to be a second battery in the engine compartment on the right side near the windshield. Inasmuch as the car is not an 330e nor an M model with mild hybrid, what is the second battery for?

[Jtw318]

Originally Posted by lmgee

I have a 2021 330i xDrive. I noticed there appears to be a second battery in the engine compartment on the right side near the windshield. Inasmuch as the car is not an 330e nor an M model with mild hybrid, what is the second battery for?

Aren't the 2021s a mild hybrid?

I could be wrong obviously, but sounds like it was fitted with the 330e battery? lol. I think in the none E's that spot is just empty.

Have a picture?

[G22b58]

Can you read the label? I suspect it is a 12V Li-Ion battery. My understanding is that these are better at cycling charge in order to save fuel and not cycling the starter lead battery as much.

[lmgee]

Thanks G22b58, it seems that you were right on target!

[G30M]

my car is a mild hybrid and does not have this battery. the space is empty, very tempted to put a bag of fruits/potatoes in there when i visit the grocer

[G22b58]

I thought "Imgee" found the secondary 12V Li-Ion battery in the same location instead of the MHEV-battery. My MHEV M440i has a 44V Li-Ion (440Wh) in the indicated location (in section Mild Hybrid page 371 in my owner's manual)

[G30M]

thanks, so some cars have both a lead acid battery and a 12V li ion battery (AND a 44V Li ion battery!!)

[G22b58]

MHEV models have the 44V Li-Ion battery on the (cars) right side in the engine compartment. It is my understanding that "Imgee" found that the non-MHEV 330i instead has a 12V Li-Ion at the same place instead of a MHEV battery.
If you don't have a 44V Li-Ion battery at this place in your M340i, isn't your car the earlier model (without 48V system)?
Do you have a Stop/Start-disable button next to the engine Start-Stop button?

[G30M]

my car has the battery charging and discharging on the energy flow section and the dealer says it has mild hybrid, but empty space for my grocery

[k4sh_90]

Mine is a 20, and has the second battery. It's a dual supply system, I think primarily to reduce battery wear with the auto start/stop and running vehicle electronics.