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01-07-2025, 11:50 AM | #1 |
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Battery Not Charging
Hey All, looking for some troubleshooting help from people who know more than me about this issue!
I think my car is having an issue with its battery. Two weeks ago I came out to a completely dead car and it had to be jumped to start. Fine, battery was dead no problem. Car went to Indy for a new OEM battery that was coded properly. I do take mostly shortish trips <15 minutes daily so I am keeping it on a battery tender to keep battery happy. However, the tender never goes fully green. I can leave it on there for 48 hours and its still not showing as fully charged. I have a CTEK 7002 and another tender that both work fine on my other car so its not the tender. Tender shows red whether hooked up to terminals under the hood or direct to the battery. Has anyone seen this issue before? I would rule out the alternator because it should be irrelevant considering it looks like a charging issue when the car is off and parked perhaps a draw on the battery? How would I chase this down? I do also get a consistent yellow bulb warning everyday, even the day I got the new battery last week. There are no lightbulbs out in the headlight assembly [IMG] ![]() |
01-07-2025, 03:48 PM | #2 |
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A bad voltage regulator in the alternator can kill a battery. You should always get battery and alternator checked.
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01-07-2025, 04:09 PM | #3 |
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Yeah how about actually getting some empirical values posted?
Like spammy alluded to, what is the voltage with the car running? What is the OCV with the car asleep at the terminal? Get a good multi meter and record results. Also get a good scanner and scan for codes on the FRM.
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01-07-2025, 04:56 PM | #4 |
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When my battery was needing replacing I went to Advance and had the battery and alternator tested. Pretty straightforward, and the measure values can help in chasing down the issue.
Last edited by a5m; 01-07-2025 at 04:57 PM.. |
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01-07-2025, 05:12 PM | #5 | |
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01-07-2025, 09:58 PM | #6 |
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Great. Let us know the results and findings.
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01-08-2025, 09:54 AM | #7 | |
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My concern is the new battery is not charging fully. I am not understanding how it this is at all related to the alternator though. It's a new battery and the issue I am having is that the car is not charging fully when the car is completely turned off. I've never seen a tender remain on a very new battery for days at a time and not show fully charged. |
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01-08-2025, 10:53 AM | #8 | |
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01-08-2025, 11:07 AM | #9 |
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Coding =/= registering. Two different functions people often lump together as coding. I had an aftermarket interstate battery coded in with bimmercode by a previous owner, but not registered in bimmerlink. When I read the battery state in INPA there were no new entries in at all for registration date/mileage. Even seasoned bmw master techs missed that detail.
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01-08-2025, 11:53 AM | #10 | |
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Calling shop that installed new battery now. |
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01-08-2025, 01:44 PM | #12 | |
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That sounds normal right? At least from my research it is. |
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01-09-2025, 04:57 PM | #14 | |
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The target voltage is sustained 14.2v charging and with all loads on--such as max AC fan, lights on, brights on, music on loud, and all windows rolling up at the same time. The ripple describes what the diodes are doing in terms of their switching current leakage. This value will be more exacerbated with the above mentioned loads on. The target is under 500 mV as this is the maximum ripple before modules will start complaining. On this particular platform, the alternator has transistor diodes and uses the LIN bus from the DME to compensate for voltage drop. https://batteryuniversity.com/articl...ging-lead-acid
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01-10-2025, 05:48 AM | #15 | ||
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Btw as discussed in another thread, the voltage can drop towards 12v making (me at the time) believe the alternator is broken. However turns out our system is "smart" and charging to 70-80% only to save space for downhill etc charging. The lowering of alternator output should only happen when the battery is "full" i.e. 80%. If charge voltage is low and the battery still isn't charged, there is a problem. For my use case the system isn't optimal but is what it is. For interest attached a note explaining the charge system. Edit: Saw OP replaced the battery which I guess will fix the issue as it apparently didn't accept charge even with a CTEK. Last edited by Helmsman; 01-10-2025 at 05:58 AM.. |
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01-10-2025, 12:19 PM | #16 |
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That's some great reference info. From that explanation, it looks to be operational range is above 11.8v and below 14.8v. Interesting!
Although, a battery at 11.8v I suspect would def have struggles restarting the vehicle and supporting all the modules. This upper end seems to coincide with Enersys as excess voltage would cause the valve to open and off-gas. For their batteries the range to charge ideally is 14.2v to 14.5v. [page 10] https://www.odysseybattery.com/wp-co...nce-manual.pdf
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01-10-2025, 03:17 PM | #17 | |
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01-11-2025, 07:42 AM | #18 | |
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It's a super finicky car for sure with the battery. I also only started to dig into it because my battery died sending me down this rabbit hole. I've owned a few E9X cars over the years and never had to troubleshoot the battery, so hopefully this blows over and I don't have to think about it again. Also, for future reference this tender does not charge our cars, at least mine even after 48 hrs on the battery. I don't think its strong enough -https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1 The CTEK 7002 had it charged within 12 hrs however. |
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01-11-2025, 01:06 PM | #19 | |
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That tender should be perfectly fine. 750mA is enough to overcome any tiny parasitic draw. The goal is under 50 to 85mA. And the 750mA would def overcome that. I can usually test the battery voltage by simply leaving the hood open and measuring at the jump-start terminals. It's good you understand when modules go to sleep and such and how that has an effect on the OCV of the battery. So I would be curious if you measure the OCV after an extended time of the car sitting. Once when the car goes to sleep (your 12.5V) and then a day or two later. If the voltage is dropping much lower than 12.5V, then I think you might have some sort of parasitic draw happeneing. I do recall somewhere on the forum a module has been known to not fall asleep causing the battery draw. Let's see if I can try searching for this.
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01-11-2025, 01:38 PM | #20 |
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OP, here is a good idea of a video for a faulty module that is something similar to our cars. You see that the module was drawing 140 mA.
This is kinda neat.
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01-11-2025, 05:03 PM | #21 |
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Here's another piece that you might find interesting to add mate:
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