[Teutonic]

Originally Posted by MilehighM3

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.

Hello and thank you for your comprehensive reply.

I did not disconnect the 48V battery before charging the 12V trunk battery. There was no literature and indications about that. Actually, the manual lacks any kind of information about that. I did however disconnected and insulated the ground on the 12V battery before charging it. After the battery was charged, I reconnect the trunk battery.

Originally Posted by MilehighM3

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.

We presumed that the bigger amperage is what makes it work. However, the question is why the lower amperage triggers the odd behaviour, but the bigger amperage makes it work? Is there a system to protect the 48V battery? And if it is, then the bigger amperage is not damaging?
Why BMW did not explained this and provide some instructions ?

Originally Posted by MilehighM3

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.

I was thinking the same thing, to disconnect the 48V battery and try the charger after and see what happens.
A video might help, however, we can not post videos in here…

And I am confused; shouldn’t the hood be OPEN when charger is on? I believe that the manual says so.

Originally Posted by MilehighM3

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

This is also new for me. Are you saying that this battery is not a stand-alone unit, but is also connected to a kind of cooling system?

Originally Posted by MilehighM3

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.

I never knew that as those are my first MHT vehicles.
The question is, how long you will keep a vehicle at 3-4000 rpm? Is this a fast charge thing?

I will look into it and get back with my results.

Thank you again for your help! I really really appreciate it!

[MilehighM3]

Sorry for the late reply, been busy. I almost created and posted a YouTube link for this but here's a few pics to show the process of disconnecting the 48v battery to charge your 12v in storage.

The battery charging in idrive is found under driving info, power flow to charge your 48v battery.


I hope this helps. Let me know if you're successful and what the specs are again on your 12v charger.

Edit: mobile uploads jumbled the order of the pictures. 🤦🏻*♂️ hopefully you get the idea/process. 3,1,2.4.5 for disconnecting the 48v system.

[Teutonic]

Originally Posted by MilehighM3

Sorry for the late reply, been busy. I almost created and posted a YouTube link for this but here's a few pics to show the process of disconnecting the 48v battery to charge your 12v in storage.

The battery charging in idrive is found under driving info, power flow to charge your 48v battery.


I hope this helps. Let me know if you're successful and what the specs are again on your 12v charger.

Edit: mobile uploads jumbled the order of the pictures. 🤦🏻*♂️ hopefully you get the idea/process. 3,1,2.4.5 for disconnecting the 48v system.

Thank you for your efforts!

I charged the big trunk battery via trunk after disconnecting it, using the NOCO 5 charger.

I will however report back if your suggestion will work as soon as I will try it.

Thank you again for everything!

[koi8r]

MilehighM3 , could you please elaborate on the 30A charger? Where is it documented? And also if you can recommend any chargers on the market that can do that? Most of chargers, at least on Amazon are "smart" chargers that do not produce nearly as much.
I attempted to charge my car with CTEK 7002 , and I measured a bit over 6 AMP on the wire. Though after many hours chargers finished the cycle, but I heard that motor activation sound every few minutes as many describe here.

Originally Posted by MilehighM3

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.

[Teutonic]

Originally Posted by MilehighM3

Sorry for the late reply, been busy. I almost created and posted a YouTube link for this but here's a few pics to show the process of disconnecting the 48v battery to charge your 12v in storage.

The battery charging in idrive is found under driving info, power flow to charge your 48v battery.


I hope this helps. Let me know if you're successful and what the specs are again on your 12v charger.

Edit: mobile uploads jumbled the order of the pictures. 🤦🏻*♂️ hopefully you get the idea/process. 3,1,2.4.5 for disconnecting the 48v system.

Hi, I have replied to you and was waiting for your reply, as I was under the impression that your are very involved from the technical point of view... any input is greatly appreciated! I still cannot find the answer for my charging problem. BMW tech is suggesting a 25A charger or higher. However, it seems that a charger higher than 10% of the battery power (this one is an 80Ah), might damage the battery. Can you please let me know your thoughts? Thank you.

[Teutonic]

Originally Posted by koi8r

MilehighM3 , could you please elaborate on the 30A charger? Where is it documented? And also if you can recommend any chargers on the market that can do that? Most of chargers, at least on Amazon are "smart" chargers that do not produce nearly as much.
I attempted to charge my car with CTEK 7002 , and I measured a bit over 6 AMP on the wire. Though after many hours chargers finished the cycle, but I heard that motor activation sound every few minutes as many describe here.

Hello, Did you find out a answer to this?

[CarniVert]

Originally Posted by 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…

Picked up an M440i Convertible a few weeks ago and hooked it up to the CTEK MXS 5.0 that I used on my last BMW. I immediately experienced the noises and activation sounds every couple minutes as described in your thread and other similar threads.

The common theme in most of the threads is that the behavior doesn't seem to occur with 25A or higher chargers like those used in mechanic shops or showroom floors, so I went ahead and purchased a CTEK PRO25S battery maintainer to hopefully confirm a solution.

I connected the PRO25S, hood open, car locked. It charged to full and went to float in about an hour. No noises or activation sounds from the car. My only concern is although the website specs state AGM compatible, there is no specific AGM mode like the MXS series had. I sent an inquiry to CTEK to see if they can provide some clarification.

So far so good though. I will update if there are any issues with the car or battery life. The professional charger is pricey compared to a regular consumer models, but simpler than any of the workarounds I have read about so far.

[G30M]

i use a CTEK MX5 and it charges the AGM

not sure about charging the 48V - i think it only charges when you drive?

[Teutonic]

Originally Posted by G99M5

i use a CTEK MX5 and it charges the AGM

not sure about charging the 48V - i think it only charges when you drive?

We are talking about a specific problem that apears only on the G80 40 B52 hybrid set-up configuration.

[G22b58]

Originally Posted by Teutonic

Yes, that is true, confirmed as well by my tech and another tech here on the thread.
The problem is that this charging is fast but heats up the battery ...

...
Also, the professional charger they use in the dealerships is able to adapt to the requirements of the vehicle and they have certain functions and they reduce the amount pushed based on a permanent battery reading, while the 25A off market chargesr are just pushing 25 A straight. Noco is a very good product as I own the 5 and the 10, but when I talked to them they confirmed that their 25-50 chargers are pushing that Ah straight. ...

I have followed some of these threads and did some testing and measurements on my M440i MHEV. I have not had a need to charge my 12V battery so this was just testing out of interest (and i preparation to know what works if needed). Further, I don't have an outlet where I park but I have a "CTEK CS Free" that initially is capable of supplying up to 20A.

My guess is that the MHEV system in these cars does something funny for a while after connecting a charger while consuming a high current. I haven't measured the current to the 12V battery but the voltage at the charging posts stays normal so my conclusion is that the current to the battery is not too high. As can be seen in my voltage/current plot the current rise to 17.5A at the beginning but then reduces while the voltage increase to a normal charging voltage of 14.1V. A car charger which is specified to be used on a battery while still being connected to the car should be safe to use even with a high current rating because it will make sure that the voltage doesn't exceed 15V or so. No cycling of click noises was heard.

[Teutonic]

Originally Posted by G22b58

No cycling of click noises was heard.
Attachment 3003436

20 A is higher than 5 or 10 and pretty close to the minimum of 25 (or suggested one).
The problem is that the clicking is present in some models and that is worrysome. I will not leave that charger in there and have that grinding and clicking noise non stop as I don’t believe is ok; ai contraire.

(In regards with your CTEK CS FREE, is intended for Lead acid /Lithium-ion so not sure how that works on the trunk AGM battery).

Either way, 20 A still seems aggressive for the battery charging requirements. The 5 max 10 are suggested for the battery as they are more lenient.
Probably if you use the regular 5 or 10 Noco, you will experience the same problem?

As mentioned before only my M340 does that.

So the problem is still pending…

[G22b58]

This is just a guess, but a stronger charger might allow the car to get pass what ever it does while requiring the high current to get it to shut down and let the charger charge the battery. Notice the sudden change in both current and voltage at about 1 minute in my plot. After that the charger keeps the voltage at 14.1V and the current gradually decreases as expected (the battery was not discharged). The voltage when the current was high was not remarkably high so I beleave that the current was consumed by something else than the 12V battery. And yes CTEK specifies it for "12 V: WET, MF, Ca/Ca, AGM, EFB, GEL, LiFePO). The same for CTEK PRO25S which I assume should work for you.

[Teutonic]

Originally Posted by G22b58

This is just a guess, but a stronger charger might allow the car to get pass what ever it does while requiring the high current to get it to shut down and let the charger charge the battery. Notice the sudden change in both current and voltage at about 1 minute in my plot. After that the charger keeps the voltage at 14.1V and the current gradually decreases as expected (the battery was not discharged). The voltage when the current was high was not remarkably high so I beleave that the current was consumed by something else than the 12V battery. And yes CTEK specifies it for "12 V: WET, MF, Ca/Ca, AGM, EFB, GEL, LiFePO). The same for CTEK PRO25S which I assume should work for you.

Thank you for your reply.
Based on previous replies I also have the same presumtion in regards with bigger amps pushing through.
I probably need to buy a bigger charger, yet, again my X4 which is also MH takes the 5 or 10 Noco with no issues.
I am more interested in why does that and why BMW did not come up with an explanation as the chargers they are selling through BMW part Dpt are maximum 5 Amps, and obviously do not work.

I still want an official answer and charging steps.

[G22b58]

Oh, so the X4 can now be charged with a 5A charger?
Earlier you wrote:
"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."

What, do you think, is the difference, did the X4 get a firmware update?
Is there a difference in how much charge there is in the 48V battery when you charge now compared to earlier?

[StanDiego]

Originally Posted by Teutonic

Thank you for your reply.
Based on previous replies I also have the same presumtion in regards with bigger amps pushing through.
I probably need to buy a bigger charger, yet, again my X4 which is also MH takes the 5 or 10 Noco with no issues.
I am more interested in why does that and why BMW did not come up with an explanation as the chargers they are selling through BMW part Dpt are maximum 5 Amps, and obviously do not work.

I still want an official answer and charging steps.

This is of no help to your request for an official answer and charging steps but just a reference point to how another model relates (or not).

First of all, I'm a BMW newby, took delivery of my very first BMW at the end of August, a '22 Z4 30i (B46TU engine).

Recently, I was surprised to discover my Z4 has a second battery (and it's only used in the 30i Z4 variant, not M40, though also used in many other BMW models). In addition to the 80a AGM in the trunk, it has an LG Li-Ion 10Ah, 132Wh, 13.2v battery that looks similar to your battery and is located in a similar location in the engine compartment. It's been challenging to find info on this but apparently BMW calls it a dual storage system, suggesting it may be significantly different than your mild hybrid system. FWIW, both my NOCO 5 and NOCO 10 work as expected. I ran across the following document in a separate forum describing the dual storage system which I believe came from https://bmwtechinfo.bmwgroup.com:

ST1856 General Vehicle Electronics 2018.pdf

Perhaps you can find something on your MHT at that site though sadly there is a fee to access it.

[StanDiego]

Originally Posted by Teutonic

I still want an official answer and charging steps.

This is of no help to your request for an official answer and charging steps but just a reference point to how another model relates (or not).

First of all, I'm a BMW newby, took delivery of my very first BMW at the end of August, a '22 Z4 30i (B46TU engine).

Recently, I was surprised to discover my Z4 has a second battery (and it's only used in the 30i Z4 variant, not M40, though also used in many other BMW models). In addition to the 80a AGM in the trunk, it has an LG Li-Ion 10Ah, 132Wh, 13.2v battery that looks similar to your battery and is located in a similar location in the engine compartment. It's been challenging to find info on this but apparently BMW calls it a dual storage system, suggesting it may be significantly different than your mild hybrid system. FWIW, both my NOCO 5 and NOCO 10 work as expected. I ran across the following document in a separate forum describing the dual storage system which I believe came from https://bmwtechinfo.bmwgroup.com:

Attachment 3004079

Perhaps you can find something on your MHT at that site though sadly there is a fee to access it.

[BMWGirlFL]

Originally Posted by Teutonic

Thank you for your reply.
Based on previous replies I also have the same presumtion in regards with bigger amps pushing through.
I probably need to buy a bigger charger, yet, again my X4 which is also MH takes the 5 or 10 Noco with no issues.
I am more interested in why does that and why BMW did not come up with an explanation as the chargers they are selling through BMW part Dpt are maximum 5 Amps, and obviously do not work.

I still want an official answer and charging steps.

Responsive?
https://static.nhtsa.gov/odi/tsbs/20...12793-9999.pdf

[Teutonic]

Originally Posted by StanDiego

This is of no help to your request for an official answer and charging steps but just a reference point to how another model relates (or not).

First of all, I'm a BMW newby, took delivery of my very first BMW at the end of August, a '22 Z4 30i (B46TU engine).

Recently, I was surprised to discover my Z4 has a second battery (and it's only used in the 30i Z4 variant, not M40, though also used in many other BMW models). In addition to the 80a AGM in the trunk, it has an LG Li-Ion 10Ah, 132Wh, 13.2v battery that looks similar to your battery and is located in a similar location in the engine compartment. It's been challenging to find info on this but apparently BMW calls it a dual storage system, suggesting it may be significantly different than your mild hybrid system. FWIW, both my NOCO 5 and NOCO 10 work as expected. I ran across the following document in a separate forum describing the dual storage system which I believe came from https://bmwtechinfo.bmwgroup.com:

Attachment 3004079

Perhaps you can find something on your MHT at that site though sadly there is a fee to access it.

My 2021 BMW X4 3.0 i is pretty much like yours. Charging works fine with both 5Ah and 10 Ah chargers.
The M340i gives me headaches as it is different.

[Teutonic]

Originally Posted by BMWGirlFL

Responsive?
https://static.nhtsa.gov/odi/tsbs/20...12793-9999.pdf

Thank you for your reply and input.
But no, is not responsive. We are talking about charging the 12 V AGM (main) trunk battery, not about the small 48 V engine compartment one; that one charges pretty fast when vehicle runs.
No, this does not address the charging issue that we encounter when we are trying to use a charger via under the hood connection (as per manual), which consist in a electric motor noise followed by a click in the 48V battery area -> which resets the charger to start again from zero. Even with the 48 V battery disconnected, the behaviour is the same.
Either way, even your instructions show how overly complicated everything is for not much gain…
And BMW still didn’t come up with a proper procedure. My mechanic treid two other new vehicles form the dealer lot and they all behave the same with three different chargers; except his shop professional one which is huge and no regular guy owns…

If you can find the answer to the 12V battery charging procedure (beside the book that doesn’t help), I will be interested.

Thank you again!

[VINCER0]

Originally Posted by MilehighM3

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.

Can you elaborate on this because the MHT in 2021+ M340i have the starter/alternator decouple from the motor during acceleration to improve emissions and performance...and recouples to charge the battery during braking, deceleration, and coasting. It also occasionally recouples during idle to temporarily charge for a few seconds so that the battery doesn't run down too low.

So this is interesting are you revving the engine in sport mode while driving or in neutral?

[MilehighM3]

Originally Posted by VINCER0

Can you elaborate on this because the MHT in 2021+ M340i have the starter/alternator decouple from the motor during acceleration to improve emissions and performance...and recouples to charge the battery during braking, deceleration, and coasting. It also occasionally recouples during idle to temporarily charge for a few seconds so that the battery doesn't run down too low.

So this is interesting are you revving the engine in sport mode while driving or in neutral?

Park

[jdq1956]

I purchased my 2021 M440i with a BMW provided trickle charger. After having the charger on for 4 months it remained hot (hood open) even though it eventually got to the last charging level. It made the car whine. Worse of all it twice knocked out my Sirius radio requiring a computer replacement (the first time I thought it was a fluke. Has anyone heard of BMW addressing this problem?