vernors

Got a 2010 535i and it has killed a few batteries over the years, and lately a relatively new (2 years old) battery has been draining oddly quickly. A couple days ago I drove about an hour with one stop and then spent 20 minutes or so trouble shooting a 93C3 code, which I think is the passanger occupancy sensor. Ignition was 'on' during this time. No audio playing, no AC on, nada.

What struck me as weird was that the battery drained out in those 20 minutes or so of me messing with INPA. So I pulled it, had it tested, and 'confirmed' that it's fine.....granted, I'm going off what AutoZone said of the battery's health.

I've had a few issues lately where the battery doesn't seem to be holding a solid charge, but also assume that AutoZone would know if it wasn't in good shape.

So, it makes me wonder if the battery cable (part number 61126989780) could be bad and causing some sort of drain. No buring or damage is obvious, and I have never smelled smoke.

Anyone run into this before?

Thanks,
V

donpb

AutoZone does not have mechanics working there. I've had to prove that my battery was bad because well they're not mechanics. I was told my battery was good when it was not.

See this thread, Is My Battery Bad? - 5Series.net - Forums.

Load test usually reveals the truth. Or if you own a device that shows the battery charge histogram, that's my go to test.

vernors

Fair point, I even asked the guy how accurate his tester was...which took about 10 seconds...and got sortof a shrug and 'good' answer.

I'll check load and see. While I had it out I fully charged it overnight.

Thanks for the help.

V

vernors

Fully charged last night, installed a couple hours ago. Just checked it, engine off, ignition off, 12.4v.

Ignition on 12.2 and flickering to 12.1.....sigh....

donpb

NOTE: With the load test explained in that link, the rebound part of the test is the key. If the voltage rebounds fast, it's a bad battery. An auto parts store used a load tester on mine, which the battery failed and then they knew the battery was bad. He was like, I didn't do load test. They do have a fancy machine that missed it. I contacted the manufacturer, and they said their machine should have caught that. They claimed the machine was bad, but I doubt that. I more so feel their machine doesn't check the voltage rebound time.