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| 09-13-2017, 01:03 PM | #23 |
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Ok, so i just put the voltmeter to the battery. It has been five to six days since i checked it last, so it was 12.06 at last check, and now it is at 11.79. Not sure if that means anything, but some online searching shows a battery below 11.88 is fully discharged. Per this page: http://www.aa1car.com/library/battery_runs_down.htm
I was also reading that the charging system needs to get some sort of volt reading from the battery to determine what type of current to send to the battery, and if it doesn't get anything the system will stop charging the battery. Is that true? I will hook the battery up to my charger for a day before taking it to get load tested. I believe it should be fully charged before getting tested for an accurate reading, is that correct?
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Last edited by houtan; 09-13-2017 at 01:13 PM.. |
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| 09-13-2017, 07:19 PM | #24 |
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Yeah fully charge the battery before load testing but based on your measurements i wouldn't hesitate to replace the battery. BMWs are sensitive to weak batteries. Not so much the N55 but N54 cars would do lots of strange things with a weak battery.
The DME will assess the condition of the battery using the IBS if it is present and working properly. If the IBS is absent or disconnected, the DME will use its own internal measurement to determine charging regime but it will be at a fixed failsafe voltage. On late model BMWs like ours which have IGR (intelligent generator control with brake energy recuperation), it is NOT rare to see the idle voltage at or slightly below 12V. This is where old school guys will get caught out. Another thing is, if your alternator has lost communication with the DME then it is possible the alternator is not putting out anything. It is not like a conventional alternator. These only have two connections - the BSD line and the positive cable. Last edited by juld0zer; 09-13-2017 at 07:26 PM.. |
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| 09-16-2017, 01:03 PM | #25 |
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Ok, so a little update.
On 9/13 I charged the battery overnight from the terminals under the hood in preparation to get it tested. On 9/14 I pulled the battery out of the car, showed 13.8 volts. I also took it to get tested at an auto parts store the same day, and the result was the battery was good. When I got home, I checked the volts and it read 13.57. On 9/15 I checked the volts and it read 12.96. On 9/16 I checked the volts and it read 12.91. Based on those results, can I assume the battery is holding charge fine? Since it was holding charge, I went ahead and reinstalled the battery for now. I also tried to check the condition of the voltage regulator, and failed. When I tried to unscrew the Phillips head screws, two loosened kind of easily, the bottom too were on much much tighter, and the heads completely stripped. I was so dang mad! haha. Oh well, if it is the regulator, I am going to just have to replace the alternator too. So what I am going to do next is reflash my map and drive the car. If the code show up again during a drive, I am going to check voltage at the alternator to see if that is why the dme is showing no charge. I am also leaving the n20 sensor on for now. Open to other recommendations/courses of action if you guys have any.
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| 09-16-2017, 06:12 PM | #26 |
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Your engine is N54 or N55? I seem to remember you had the latter and the voltage regulator is not sold by BMW.
On 9/14 i would say that has surface charge on it |
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| 09-16-2017, 08:53 PM | #27 |
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I am N55. I thought I found an oem part for the voltage regulator but I didn't confirm if it would work.
Will update once I have a chance to drive the car for a few days. |
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| 09-17-2017, 12:15 AM | #28 |
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Had a chance to start my car real quick. At idle, the volts at the battery is 14.1, and at the alternator its 14.3. Now I'll have to wait for the code to occur while driving and then do the same checks again.
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| 09-20-2017, 10:11 AM | #29 |
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Just an update. Drove my car to work yesterday, about 30 min drive, no code. Drove home, about 50min, no codes.
I am hoping the issue was a bad flash. Maybe the disconnecting of the Tmap and Maf with battery connected coupled with a flash for the n20 tmap sensor caused a bug when I loaded the flash. Not sure. Hoping to get a long drive through the canyons this weekend to see if higher temps cause an issue. fingers are crossed.
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Last edited by houtan; 09-20-2017 at 10:17 AM.. |
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| 12-04-2017, 05:34 PM | #31 | |
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Quote:
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| 09-29-2018, 10:34 AM | #33 |
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Long overdue update. About a month after this thread started , I went to a half mile event in October 2017. It was 90 plus degrees. All was good until the last run of the day, when this happened:
Scared the crap out of me. After Kerri f the car sit for 30 min she started up and went straight on the trailer. Never had the red battery or car meltdown issue again until about a year later when the red battery light came on driving home and voltage via mhd was in the 11s. Didn’t really troubleshoot anything because if time but stumbled across these two threads today. https://www.e90post.com/forums/showt...0#post23783060 https://www.e90post.com/forums/showt...3#post23783063 I installed Delphi coils at the same tune as my ps2 install and it appears these have been the issue the entire time!
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The Denso alternators are generally pretty reliable
