[Danny81bby]

Morning

My partners 2018 2 series coupe came up with a battery discharged warning yesterday. I checked the voltage and it was 12.02 after being sat for a few hours. Checked startup which dropped to 9.45 which i know is low. When running and charging it's around the 14.6 with all electrical turned on etc. Took it for an hours drive with everything turned off to allow for a proper charge. Checked voltage this morning and its at 11.98. Does this mean I need to get battery changed or could it be something pulling the voltage down over time?

Thank you

[MarcoZandrini]

Sure sounds like the battery is going bad. This is what I recommend: https://www.fcpeuro.com/products/aut...vD_BwE#fitment

[ggggbmw]

What is the voltage on the battery when car is powered off after running for a while? An AGM battery should be around 12.6 V when in a charged resting state. If it's below that, you have bad/failing cell.

If it's at ~12.6 V when the car is off, it could be failing battery, or it could be a high-drain scenario. The acid test is to put an amp meter on it, with the car turned off. Keep in mind it can take up to 20 minutes for all iDrive components to finally fall asleep and get an accurate resting draw. It can be useful to monitor voltage during this falling asleep process also to watch for dropping voltage. It shouldn't change much.

After 30 minutes, you should see less than 100 milliamps of current draw. If it's more than that, something is sucking up too much power when it should be off.

Also, how old is the battery? An original BMW battery will have a date code stamped on one of the posts with the month and year of production. If it's over 6 years, you are probably due to replace it.

[Danny81bby]

Thanks very much for the replies I'll try what you recommended, much appreciated. Also reading up on battery replacement it says you have to register the new battery with the on board computer. Never heard of this before. The hardware/software to do this is like £100. Doesn't seem right to me

[aerobod]

Originally Posted by Danny81bby

Thanks very much for the replies I'll try what you recommended, much appreciated. Also reading up on battery replacement it says you have to register the new battery with the on board computer. Never heard of this before. The hardware/software to do this is like £100. Doesn't seem right to me

Battery registration is common with many manufacturers these days, especially for cars that have high electrical demands. If you don’t do it the car charging system will assume an old battery based on the previous registration stored, leading to too high current being applied (as battery resistance rises with age) causing the new battery to get hotter than designed, out-gassing more hydrogen than expected and shortening it’s life.

[nazali]

get a solar BA9 to test,
make sure the car is asleep
otherwise any tests you do are pretty much worthless with a meter

on my channel I have a longer version of this

Originally Posted by Danny81bby

Morning

My partners 2018 2 series coupe came up with a battery discharged warning yesterday. I checked the voltage and it was 12.02 after being sat for a few hours. Checked startup which dropped to 9.45 which i know is low. When running and charging it's around the 14.6 with all electrical turned on etc. Took it for an hours drive with everything turned off to allow for a proper charge. Checked voltage this morning and its at 11.98. Does this mean I need to get battery changed or could it be something pulling the voltage down over time?

Thank you