Quote:
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.
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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.
Quote:
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.
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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 ?
Quote:
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.
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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.
Quote:
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
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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?
Quote:
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.
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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!