Hello all,
One of my 2021 BMW’s is a summer toy and I do not drive it in the winter.
The battery gets discharged pretty fast and I get the message that battery is low. Today I got a message that was saying something like “extremely lor battery level or something.
For this reason I would like to charge it or put a trickle charger on it.
The vehicle is -as almost all new ones- equipped with a Mild Hybrid Technology which includes a second 48V Lithium battery under the hood on the passenger side.
The problem is that whatever charger I have (mine are amatorial ones) do not work.
The chargers are connected as the manual suggests via red connector and ground connector under the hood. BMW interdicts specifically in the book to charge the AGM big battery through the trunk as that may affect the system.
But they miserably do not offer any advice about charging it except “connect under the hood” process, which actually does not work.
I have a BMW trickle charger and it doesn’t work as the battery is an AGM.
I do have, however, an OEM BMW charger (CTEK) and also a Noco Genius 5.
The chargers are fine for my other BMW but for some reason they do not work on my 2021’s MHT vehicles. CTEK or Noco, behave exactly the same.
Anytime you connect those chargers to the vehicle, they make a noise that is similar to a little motor, and then a click will follow. This process is repeated indefinitely without ending up in charging the big rear battery.
My mechanic tried my chargers and they do the same. He tried two brand new vehicles from the dealership lot as well with the same noise and same result.
The battery could be charged with his professional huge charger but not with mine.
Obviously, I want to avoid going under a certain voltage as that will trigger the battery electronic board to declare the battery dead which will automatically force me to buy a new one.
Why on earth BMW put those electronic boards on the AGM batteries is out of my understanding as any regular new battery can actually be charged normally.
Anyway, both my 2021’s came with MHT and they both behave the same when the charger is connected.
As many members have already a 2021 or later that is equipped with this Mild Hybrid Technology, I presume there is someone in here that had the same problem or is trying to charge or maintain the battery.
Or maybe a fellow technician can suggest something, as I do not own a such professional battery charger like the dealership.
If you had a similar problem and found a solution, please be kind and share it.
Thank you for your help!
EDITED
Connected Threads:
https://g05.bimmerpost.com/forums/sh....php?t=1786709
https://g20.bimmerpost.com/forums/sh...6#post29583006