[twin's Turbo]

Here is what I can find on the Battery.

"The Power Control Unit (PCU) is mainly installed to avoid or reduce the energetic load of the vehicle battery during automatic engine stop (MSA). The reduction in the cyclisation (= number of cycles of the automatic engine start-stop function) extends the service life of the vehicle battery.

The preconditions for adjusting the energy management are derived from the usage of the vehicle. When the engine is running, the auxiliary battery is loaded from the vehicle electrical system basic version. During the phases with automatic engine start-stop function stop, the energy from the auxiliary battery is fed back into the vehicle electrical system basic version"

"The auxiliary battery is an AGM battery. On vehicles with dual storage system, the auxiliary battery is a lithium-ion battery."

I think they mean the main battery is AGM in the trunk and the front battery is Lithium-ion.

https://www.newtis.info/tisv2/a/en/g...ery/1VnYtww1lT

[danfratamico]

The 2021 BMW M340s now have an eBoost 48V mild hybrid system which allows for seamless auto start stop (ASS override button removed as well). The engine can shut off even before you fully stop the vehicle amongst other features. Anyone know if the 2020 cars with the 48V battery have these new features as well?

[TurtleBoy]

Originally Posted by danfratamico

The 2021 BMW M340s now have an eBoost 48V mild hybrid system which allows for seamless auto start stop (ASS override button removed as well). The engine can shut off even before you fully stop the vehicle amongst other features. Anyone know if the 2020 cars with the 48V battery have these new features as well?

No, the mild hybrid system was introduced in the MY21 models. The Li battery posted about in previous MYs is for certain electrical options and not the MH system.

[k4sh_90]

I have 2020 M340i with the dual battery system. So if we wanted to disconnect the battery before working on any electronic stuff, we'd have to do both to fully unplug the vehicle?

[Bland42]

Originally Posted by v_ckash623

I have 2020 M340i with the dual battery system. So if we wanted to disconnect the battery before working on any electronic stuff, we'd have to do both to fully unplug the vehicle?

Yes, everything is still powered when you disconnect the AGM battery.

[nealjay]

So when charging the battery with ctech charger in front its lition ion not agm correct?i hardly drive my car so have to charge battery

[TurtleBoy]

Originally Posted by nealjay

So when charging the battery with ctech charger in front its lition ion not agm correct?i hardly drive my car so have to charge battery

It has both but you are first charging the AGM using the terminals under the hood so use that setting. Assuming you have a mild-hybrid, make sure you keep the hood open when charging.

[anandn]

Originally Posted by nealjay

So when charging the battery with ctech charger in front its lition ion not agm correct?i hardly drive my car so have to charge battery

I’m using a CTEK MXS 5 to charge the AGM starter battery in my 2023 440i convertible. The BMW manual states that the hood must be open to charge the starter battery. I keep it ajar after connecting to the dummy terminals in the engine bay. Car is locked. Charger is working fine. I don’t think the 48v lithium ion battery can be charged using a CTEK charger. The manual doesn’t say that the 48v battery requires charging,

[TurtleBoy]

Originally Posted by anandn

I’m using a CTEK MXS 5 to charge the AGM starter battery in my 2023 440i convertible. The BMW manual states that the hood must be open to charge the starter battery. I keep it ajar after connecting to the dummy terminals in the engine bay. Car is locked. Charger is working fine. I don’t think the 48v lithium ion battery can be charged using a CTEK charger. The manual doesn’t say that the 48v battery requires charging,

Once the AGM battery reaches a certain SOC, I think 70% but not sure about that, then the 48v battery will start to be charged.

[anandn]

Originally Posted by TurtleBoy

Once the AGM battery reaches a certain SOC, I think 70% but not sure about that, then the 48v battery will start to be charged.

I didn’t know that. Self discharge rates of Li ion batteries are very low. So I assume over a few months of storage, the hybrid battery will not need to be charged. I have a Volvo PHEV with a 19 kwh battery and the discharge rate over weeks is negligible. Regarding the CTEK, it charges at max current until the starter battery is at 80% and then charges at declining current to full charge. The battery is then topped off as needed to compensate for self discharge of the AGM battery.

[TurtleBoy]

Originally Posted by anandn

I didn’t know that. Self discharge rates of Li ion batteries are very low. So I assume over a few months of storage, the hybrid battery will not need to be charged. I have a Volvo PHEV with a 19 kwh battery and the discharge rate over weeks is negligible. Regarding the CTEK, it charges at max current until the starter battery is at 80% and then charges at declining current to full charge. The battery is then topped off as needed to compensate for self discharge of the AGM battery.

The 48V battery can become discharged for various reasons, there is an SIB on it.

48 V battery may become totally discharged, and possible replacement needed if:
a) The vehicle has been charged using a 12 V charger with the hood closed during a long stationary period, the. For example, the showroom or storage.

b) Vehicles stored for an extended period connected to a low output solar or trickle charger.

c) Vehicles stored for an extended period with no charger connected and not properly maintained 12 V battery.

https://static.nhtsa.gov/odi/tsbs/20...88948-9999.pdf

[zazzau]

Originally Posted by TurtleBoy

It has both but you are first charging the AGM using the terminals under the hood so use that setting. Assuming you have a mild-hybrid, make sure you keep the hood open when charging.

I leave mine closed -- just not latched.

[anandn]

Originally Posted by TurtleBoy

The 48V battery can become discharged for various reasons, there is an SIB on it.

48 V battery may become totally discharged, and possible replacement needed if:
a) The vehicle has been charged using a 12 V charger with the hood closed during a long stationary period, the. For example, the showroom or storage.

b) Vehicles stored for an extended period connected to a low output solar or trickle charger.

c) Vehicles stored for an extended period with no charger connected and not properly maintained 12 V battery.

https://static.nhtsa.gov/odi/tsbs/20...88948-9999.pdf

Good info. Thanks. This is in the bulletin
:Trickle chargers (< 20-amp output) or solar chargers will not be able to charge the 48 V battery, but could prevent further discharge to the 48 V battery when the 12 V battery is properly maintained to optimal SOC.”

CTEK trickle chargers will not able be charge the hybrid battery. Li ion batteries discharge very slowly and at a lower rates when not fully charged. My Volvo manual states that the hybrid battery should be stored at less than 25% charge for longevity. I wouldn’t worry about discharge of the hybrid battery as long as there is a trickle charger attached to charge the starter battery. A few months of storage should not kill the hybrid battery in my judgment.
https://batteryuniversity.com/articl...f-discharge-do

[nealjay]

Originally Posted by TurtleBoy

It has both but you are first charging the AGM using the terminals under the hood so use that setting. Assuming you have a mild-hybrid, make sure you keep the hood open when charging.

oh okay thanks imma try it in a. few days hopefully it work s its at 60%

[TurtleBoy]

Originally Posted by nealjay

oh okay thanks imma try it in a. few days hopefully it work s its at 60%

Some folks were able to get it charged after having it hooked up for two or three days, hopefully you will be successful.

[anandn]

Originally Posted by TurtleBoy

Some folks were able to get it charged after having it hooked up for two or three days, hopefully you will be successful.

Should be much faster than that. Using the CTEK MXS 5, a 90 Ah BMW AGM discharged battery should be charged within 24h. Mine went to 80% in less than 20h and to the floating charge setting within 24h. My 2023 440i sat at the dealer for six weeks because I wasn’t in town to take delivery and the battery was severely discharged. Only thing to keep in mind is that CTEK chargers (which is also what BMW sells with the BMW logo) get pretty hot when it charges at max amperage in the bulk charging phase and should be kept on on a cool surface. Not covered or stuck in a corner without adequate air flow. The charger doesn’t have an in built fan to dissipate heat.

[TurtleBoy]

Originally Posted by anandn

Should be much faster than that. Using the CTEK MXS 5, a 90 Ah BMW AGM discharged battery should be charged within 24h. Mine went to 80% in less than 20h and to the floating charge setting within 24h. My 2023 440i sat at the dealer for six weeks because I wasn’t in town to take delivery and the battery was severely discharged. Only thing to keep in mind is that CTEK chargers (which is also what BMW sells with the BMW logo) get pretty hot when it charges at max amperage in the bulk charging phase and should be kept on on a cool surface. Not covered or stuck in a corner without adequate air flow. The charger doesn’t have an in built fan to dissipate heat.

Yes it should be but, at least in the past, most charging attempts seems to either not be successful or take a long time. I'm hoping that a fairly recent software update took care of the problem since the number of folks posting about charging issues has really decreased.

[bavarianride]

Originally Posted by anandn

Should be much faster than that. Using the CTEK MXS 5, a 90 Ah BMW AGM discharged battery should be charged within 24h. Mine went to 80% in less than 20h and to the floating charge setting within 24h. My 2023 440i sat at the dealer for six weeks because I wasn’t in town to take delivery and the battery was severely discharged. Only thing to keep in mind is that CTEK chargers (which is also what BMW sells with the BMW logo) get pretty hot when it charges at max amperage in the bulk charging phase and should be kept on on a cool surface. Not covered or stuck in a corner without adequate air flow. The charger doesn’t have an in built fan to dissipate heat.

Yes CTEK 4.3 gets hot too, so I usually rest it on garage floor.

I have done 2-3 charges overnight so far(took delivery 4/2021) without issues.

[anandn]

Originally Posted by TurtleBoy

Yes it should be but, at least in the past, most charging attempts seems to either not be successful or take a long time. I'm hoping that a fairly recent software update took care of the problem since the number of folks posting about charging issues has really decreased.

I don’t know if were any software updates. I read the other thread on this topic. It seems to me that folks are not waiting long enough or getting worried about the charger getting hot or opening the door to check for messages on the screen. For whatever reason, the CTEK MXS I am using (with the eight stage charging process) takes a long time in stage 3, the bulk charging phase. In my car, it took close to 16h then rapidly went to stage 7. I assumed that it was because the car sat at the dealer for over a month. But we had a power outage recently and the charger automatically went back to stage 3 and it took another 16 h to reset to stage 7. Don’t know why. I called CTEK and didn’t get a satisfactory answer. I was informed that heat buildup in the charger in stage 3 was normal. The charger does have a 15 amp fuse and supposedly will shut off if it gets too hot. I use the same charger in my 2022 Volvo XC60 PHEV and the charging time was significantly shorter. It also uses an AGM starter battery.

[TurtleBoy]

It is not confined to a CTEK as I used a Schumacher. Actually I don't think it is the charger at all but rather the vehicle never shutting down and the battery/charge being used. Mine was constantly making noises and the charging progress was going very slowly. I then switched it from maintainer to a 30amp quick charge and the battery SOC rose much more rapidly.

[anandn]

Originally Posted by TurtleBoy

It is not confined to a CTEK as I used a Schumacher. Actually I don't think it is the charger at all but rather the vehicle never shutting down and the battery/charge being used. Mine was constantly making noises and the charging progress was going very slowly. I then switched it from maintainer to a 30amp quick charge and the battery SOC rose much more rapidly.

Yes that's what I am encountering as well. The car is a nervous wreck and seems to be constantly running some diagnostic or another and making all sorts of whirring sounds. Having to leave the hood unlatched for a battery charger doesn't seem to put the car in sleep mode. My BMW app shows that the hood of my car (currently stored in my garage in Florida) is open and that the car is unlocked. I locked the doors before leaving. Strange.

[bavarianride]

I think I did lock and then unlock the car to turn off all electronics, then charge through under hood jump terminals with hood opened. I will try this again this week and report back.