Charging a MIld Hybrid Technology BMW

[Teutonic]

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

[Teutonic]

Wow, I can’t believe that there is nobody here with an 2021 M340i, X4 or another newer vehicle that did not tried to charge the battery…

[Polot]

I imagine most people here are not using 2021 M340i, X4s, etc here solely as summer toys. If you are regularly using the car and you are having battery charge issues I would lean more into there is something wrong with the battery (or alternator, etc). I know you said you only use yours as a summer toy that you don’t drive in winter but it is only late December and if your new car is already having battery issues I would again suggest there is something wrong with your car.

[Teutonic]

Originally Posted by Polot

I imagine most people here are not using 2021 M340i, X4s, etc here solely as summer toys. If you are regularly using the car and you are having battery charge issues I would lean more into there is something wrong with the battery (or alternator, etc). I know you said you only use yours as a summer toy that you don’t drive in winter but it is only late December and if your new car is already having battery issues I would again suggest there is something wrong with your car.

X4 is not the toy but was mentioned as it has the same MHT system which will be omnipresent in most of the NA vehicles. He also behaves exactly the same when trying to charge it. For now M340i is kept for summer.

Anyway, With the charger on the both behave the same. It is nothing wrong with the charging system. The car was sitting since July as is located in a different area.

The 2021 X4 had the same issue as the guys that fully wraped the whole car with PPF took two weeks for the work and that consumed the battery which forced me to buy a new battery regardless the car was three months old.
Those batteries, if they reach a certain low voltage, they are dismissed by the system as being damaged and they can not be recharged. Hence, you need to buy a new one.

As mentioned above, my BMW Shop Foreman also took other two new ones from the dealership lot and they behave the same regardless if the charger is a CTEK, a BMW or a NOCO.
The battery was however succesfully charged with the professional BMW shop charger. I just was away from the car since June and if you don’t drive them, the network of computers they have literaly suck the power.
I talked to one guy at a tuning shop and he said that Ctek is working on the problem.

I just wanted to know if someone managed to avoid the system somehow and charge the big trunk battery.

[HighlandPete]

Not sure if this post is helpful or not. Seems something else may be preventing charging.

https://g20.bimmerpost.com/forums/sh...44&postcount=4

[Teutonic]

Originally Posted by HighlandPete

Not sure if this post is helpful or not. Seems something else may be preventing charging.

https://g20.bimmerpost.com/forums/sh...44&postcount=4

Thank you for your reply.
Of course you charge it with the hood open. I had BMWs before. These ones are different and for some reason, the system doesn’t let the power go to the rear battery if you use the chargers mentioned above that were successfuly used to all previous BMW models.

[DanG]

I would see what the dealers are using. My dealer has all his showroom BMWs on chargers.

[danchee]

I use a Noco charger on the wife's X7 and it charges just fine connecting to the access ports under the hood. I leave the hood open but latched when I charge and it works just fine.

I plug the charger into the wall outlet but not connected to car. Set the mode to AGM. Unplug from all. Attach to the access ports then open and close car doors to make the car up fully. Then plug charger into wall outlet. Takes a moment and then the Noco battery charge state updates to the expected level and blinks slowly as it charges.

[Teutonic]

Originally Posted by danchee

I use a Noco charger on the wife's X7 and it charges just fine connecting to the access ports under the hood. I leave the hood open but latched when I charge and it works just fine.

I plug the charger into the wall outlet but not connected to car. Set the mode to AGM. Unplug from all. Attach to the access ports then open and close car doors to make the car up fully. Then plug charger into wall outlet. Takes a moment and then the Noco battery charge state updates to the expected level and blinks slowly as it charges.

Maybe yours is not a Mild Hybrid.
It doesnt work.

Here is another thread with the same issue and with no answers>

https://g20.bimmerpost.com/forums/sh....php?t=1779237

[SteveinArizona]

Originally Posted by DanG

I would see what the dealers are using. My dealer has all his showroom BMWs on chargers.

+1

[Teutonic]

Originally Posted by DanG

I would see what the dealers are using. My dealer has all his showroom BMWs on chargers.

At least in my dealerships they are using professional ones.
I am interested in see what is happening in this case with BMW, CTEK and NOCO chargers that were just perfect to maintain and slowly charge a battery on all previous BMWs.

I don’t want a huge box. Plus, keep in mind that a dealer has the manpower to do everything, unlike us,the average Joe.

[danchee]

Originally Posted by Teutonic

Maybe yours is not a Mild Hybrid.
It doesnt work.

Here is another thread with the same issue and with no answers>

https://g20.bimmerpost.com/forums/sh....php?t=1779237

It's a mild hybrid. All 2021 X7s are mild hybrids.

[Teutonic]

Originally Posted by danchee

It's a mild hybrid. All 2021 X7s are mild hybrids.

I have a Noco 5 I think. What are you using?
I don’t get it. Both M340i and the X4 have the same clicking noise and no charging.
(See the other thread).

[danchee]

Originally Posted by Teutonic

I have a Noco 5 I think. What are you using?
I don’t get it. Both M340i and the X4 have the same clicking noise and no charging.
(See the other thread).

Sorry was out of town until now. I have the original Noco G3500 and neighbor has a Genius 5 that works as well.

[Teutonic]

Originally Posted by danchee

Sorry was out of town until now. I have the original Noco G3500 and neighbor has a Genius 5 that works as well.

It’s okay. Happy new year to you!

Beside the others, I also have the Noco 5. Unfortunately, it doesn’t work on M340i.

[MilehighM3]

Originally Posted by Teutonic

It’s okay. Happy new year to you!

Beside the others, I also have the Noco 5. Unfortunately, it doesn’t work on M340i.

Are you connecting under the hood or in the truck directly to the battery?

[barcelona]

https://x3.xbimmers.com/forums/showt...1849221&page=4
See post 80. Unsure, if that answers any of your questions. Your situation is indeed odd.

Strange your OEM BMW charger (CTEK) does not work on your MHT, yet on your non MHT cars. I have an older OEM BMW charger (Deltran) hooked under the open hood to my MHT , no clicking sound, solid green light. Car is new.

Keep us updated, as I am interested in your resolution. I can't find the 48V replacement cost (i will ask parts dept) , some BMW 48v are say $1500.

As a suggestion, try the other forum series, as many others will likely have your same or similar questions. Soon success, I am sure.

[danchee]

Originally Posted by Teutonic

It’s okay. Happy new year to you!

Beside the others, I also have the Noco 5. Unfortunately, it doesn’t work on M340i.

Try using the non-AGM 12V mode?

[Teutonic]

Originally Posted by MilehighM3

Are you connecting under the hood or in the truck directly to the battery?

Yes, of course, under the hood. i own BMW for decades.
I have three BMW as we speak so I know a lot about them.

[Teutonic]

Originally Posted by danchee

Try using the non-AGM 12V mode?

Did not try that with CTEK or NOCO as the trunk battery is AGM?

I did tried however with my old BMW charger which is a regular non AGM and I get the same behaviour.

[Teutonic]

Originally Posted by barcelona

https://x3.xbimmers.com/forums/showt...1849221&page=4
See post 80. Unsure, if that answers any of your questions. Your situation is indeed odd.

Strange your OEM BMW charger (CTEK) does not work on your MHT, yet on your non MHT cars. I have an older OEM BMW charger (Deltran) hooked under the open hood to my MHT , no clicking sound, solid green light. Car is new.

Keep us updated, as I am interested in your resolution. I can't find the 48V replacement cost (i will ask parts dept) , some BMW 48v are say $1500.

As a suggestion, try the other forum series, as many others will likely have your same or similar questions. Soon success, I am sure.

My 2012 X1 uses the 2012 OEM BMW trickle charger [deltran) and works fine.
I can also use the CTEK and the Noco 5 with the X1.

The 2021 X4 and the 2021 M340i don’t work with the CTEK. They are both MHT vehicles.
I believe that the X4 works with the Noco5 now..? Not sure, I need to try it again.

The M340i does not accept any of the chargers via under the hood, all of them induce the same behaviour with a small motor noise followed by a clicking noise on the 48V battery area. (Unfortunatley we can not post videos in this forum).

I believe that the small 48V battery is more than $1500 but I might be wrong.

As mentioned above, my shop foreman tried two other brand new 2021 M340i from the dealer’s lot and all behave absolutely identical with sam noise and same click.
They all charge however with the professional BMW shop charger via under the hood. The tech could not explain why this happens. All chargers are BMW oem except the Noco5 which I bought it as I thought it will do the job.

As my situation was desperate I disconnected my M340i trunk battery and charged it with Noco 5 directly with no issues.
Under the hood method however, doesn’t work. As you can read on my previous post, there is a link where other members whee in a same situation with MHT vehicles.
Is just that is annoying and not practical whatsoever.

I am still looking for the proper answer in regards with this.

[MilehighM3]

Originally Posted by Teutonic

My 2012 X1 uses the 2012 OEM BMW trickle charger [deltran) and works fine.
I can also use the CTEK and the Noco 5 with the X1.

The 2021 X4 and the 2021 M340i don't work with the CTEK. They are both MHT vehicles.
I believe that the X4 works with the Noco5 now..? Not sure, I need to try it again.

The M340i does not accept any of the chargers via under the hood, all of them induce the same behaviour with a small motor noise followed by a clicking noise on the 48V battery area. (Unfortunatley we can not post videos in this forum).

I believe that the small 48V battery is more than $1500 but I might be wrong.

As mentioned above, my shop foreman tried two other brand new 2021 M340i from the dealer's lot and all behave absolutely identical with sam noise and same click.
They all charge however with the professional BMW shop charger via under the hood. The tech could not explain why this happens. All chargers are BMW oem except the Noco5 which I bought it as I thought it will do the job.

As my situation was desperate I disconnected my M340i trunk battery and charged it with Noco 5 directly with no issues.
Under the hood method however, doesn't work. As you can read on my previous post, there is a link where other members whee in a same situation with MHT vehicles.
Is just that is annoying and not practical whatsoever.

I am still looking for the proper answer in regards with this.

A couple things come to mind. First off, did you disconnect the 48v battery before disconnecting the 12v on your 340? If not, reconnect the 12v and disconnect it first. This is a requirement to prevent damage to the 48v battery.

The reason I asked for battery charger location is relevant if you know how the 48v system operates. With the hood open the 48v system is de-energized automatically. To charge the 12v via the engine compartment requires at least 30a charger, your local foreman should know this.

Try disconnecting the low voltage/communication connection on the 48v battery. This is done by removing the cover over the 48v battery and locating the connector on the outside of the battery. Pull back the grey secondary lock on the connector by pulling back until it clicks, then releasing the primary lock by pinching the connector in the center downward with your thumb and pulling back. I can post a video if needed. Then connect your maintainer to the connection under the hood, careful to make sure nothing sticks up to contact the hood, and close the hood. See if the charger works this way.

You're close on the 48v cost, it's around 2k and takes a few hours labor to replace along with some coolant since it is liquid cooled.

There's also a way to charge the 48v battery via running the engine that you should be aware of if your vehicle is stored. A 12v charger cannot charge the 48v battery. It's in print that it can, but I've tested several cars and it does not change. Bring up the vehicle info in the idrive and access the power flow. Here you'll be able to see the battery charge level which is indicated by the ratio of blue sectors to black/empty. You want 2-3 sectors to be blue, indicating 40-60% charge. Put the vehicle in sport mode so you can see the tachometer and rev the engine to 3-4k until you see power flow being sent to the battery. Hold the RPMs at the point where the charging is operational until the desired charge level is achieved. I can post screenshots/videos as needed of these steps as well later today.

Sent via mobile please excuse my typos