[piglet94122]

Please help. What is the 15.4 referring to? Is it voltage or the alternator? Does any of this tell me the situation of the main battery in the back of the trunk?

5 year old vehicle with 38k miles. It takes about two seconds longer to start when overnight cold. No starting issues after the car is hot.

Battery under the trunk has not changed yet.

Does anyone change the vehicle battery under the hood? I wonder how long this one will last.

Thank you all!

[eluded]

Probably a reference your MPG average, which is either 14.5 or 15.4 which might not be the best, but at least you're enjoying life.

The BMW AGM Battery will last a long time, especially in California

[TurtleBoy]

As mentioned, that is your MPG for the Trip bucket you have selected and the other is the current MPG usage.

[piglet94122]

The # on the left is mpg. Not sure about the right #. Couple weeks ago, it went down to zero and it keep going up as I drive the car. After I charged the battery, it’s back up to 17.0. Now it’s slowly dropping to 14.9. I don’t know if the right # has anything to do with mileage or mpg. I don’t expect it would fluctuate 0 to 17 while driving.

[TurtleBoy]

Originally Posted by piglet94122

The # on the left is mpg. Not sure about the right #. Couple weeks ago, it went down to zero and it keep going up as I drive the car. After I charged the battery, it’s back up to 17.0. Now it’s slowly dropping to 14.9. I don’t know if the right # has anything to do with mileage or mpg. I don’t expect it would fluctuate 0 to 17 while driving.

The numbers are exactly what I said, they have nothing to do with the battery.

[TurtleBoy]

Look at your trip data. The average MPG for the bucket you have selected will show on the right. The figure on the left is the MPG usage at that instant. You will see that number change with throttle usage.

[AGONXF30]

Originally Posted by eluded

The BMW AGM Battery will last a long time, especially in California

I have had BMW AGM last well over 8 years. I believe with proper driving techniques and proper charge (Trickle from time to time when needed) they can go well over 10 years.

[AGONXF30]

Originally Posted by piglet94122

The # on the left is mpg. Not sure about the right #.

One is instan MPG, the other is average. There are no battery “health” or voltage indications displayed by BMW.

Originally Posted by piglet94122

Couple weeks ago, it went down to zero and it keep going up as I drive the car. After I charged the battery, it’s back up to 17.0. Now it’s slowly dropping to 14.9. I don’t know if the right # has anything to do with mileage or mpg. I don’t expect it would fluctuate 0 to 17 while driving.

It is MPG, nothing to do with battery.