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Discussion Starter #1
Hey guys, I got the high battery drain message a few days ago after going grocery shopping, but the car started fine when I came out so I figured I forgot to turn off the radio or something. Fast forward the next morning, I hop in the car to start it and the ignition comes on normally and everything but when I press the start button, the starter is super slow to turn, everything dims, but the engine does start. I am immediately presented with a bunch of abs faults and power steering faults due to low voltage. I let the car idle and charge, turn it off and back on immediately, and everything is fine. So I tried to find a drain, measured all the fuses with the car in deep sleep and nothing was drawing power. Comfort access isn’t draining it. Next morning the car wouldn’t even start, battery was too low. I had to jump it from the terminals under the hood. Drove around for an hour to charge the battery, then parked and unplugged the TCU overnight and it still drained. Next morning wouldn’t start. So repeat above process, except this time I unplugged the IBS and the car seemed to not drain overnight. Started fine and I thought “finally found the culprit”. However, I went to wash the car and because of how my hose is positioned I have to turn the car around to wash the other side. Pulled it to the spot I wash in, washed one side, got back in and turned the car around, washed the other side, then went to pull it back to where I park it and: wouldn’t start, had to jump it. I’m now at a loss. Battery is just now turning 3 years old, so I doubt that’s the problem. Voltage regulator maybe? I thought it wouldn’t be alternator related since it seems to be charging the battery fine (14.6 V at idle) but I really am not sure now. I’ll post some pics of ISTA codes when I get back to my computer but they all seem to be normal low voltage codes. Any help would be appreciated.
 

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Is 14.6 checked at battery?
 

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Have you tried using the "secret" menu? I've checked the voltage there and since changing my alternator it sits around 14.1 - 14.3.

But my battery is going bad.
 

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Discussion Starter #8
Have you tried using the "secret" menu? I've checked the voltage there and since changing my alternator it sits around 14.1 - 14.3.

But my battery is going bad.
I’ll try it from the cluster menu and see what it says. Thanks
 

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I’ve had battery drain and never found the reason (changed the alternator and regulator, went through 2 batteries). Just using a trickle charger and a serious Noco booster just on case. I have a CTEK monitoring thing and I can perfectly see the drain, gremlins ...
You can see very clearly when tje car isn’t on the charger



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Discussion Starter #10
Thanks for all your guys' help, I removed the battery and took it to Autozone to have them load test it, came back bad. Interestingly enough the battery I pulled out was a BMW branded, white case 90A Lead Acid rated for 720 CCA... not ideal lol. Anyway replaced it with a 95A AGM with 900 CCA and all seems well for the past day. When I was registering the new battery, I saw that the battery currently registered with the car was a 90A AGM so the previous owner must not have registered the lead acid when they replaced it, which is weird because its an actual BMW battery as if they would have bought it direct from the dealer. Weird. Anyway, thanks again for your help!
 

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I’ve had battery drain and never found the reason (changed the alternator and regulator, went through 2 batteries). Just using a trickle charger and a serious Noco booster just on case. I have a CTEK monitoring thing and I can perfectly see the drain, gremlins ...
Something like this?

My problem's slightly different in nature - it never shows any hesitation in starting, but it throws cogs at me and drops to limp mode if it's not regularly used. Replaced and registered battery, no change...
 

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Precisely that device yes.

Well in my case I started having all sort of codes pop up (including cogs) just coming back from a 3 hour drive. Turned the car off to “reset” and it never cranked after that (at a red light) without a jump start.
That prompted me to check and the battery was toast so I changed it thinking that was it but the new one started to go so I changed the alternator and regulator, then the IBS, measured current draw in sleep mode (door locks relocked with a screwdriver, boot and ceiling bulbs removed and waiting fir the car to go in sleep mode - never foud how to do that with INPA) pulling all and every fuse in succession : never found the culprit. If I don’t keep the car on the trickle charger, the battery will drain in a couple of weeks.


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