Is 15 volts too high for charging/alternator output?

Hello guys,
E92 m3 from 09/2011, competition packet. I have the OEM battery w 90 Ah. Its Varta brand, 90Ah w 900A AGM. Battery looks close to death. I trying to recharge it but it doesn't hold the voltage (after full recharging to 14,5V and 890A goes again low in few hours to cca. 12,3 V and 600A and then hold this values).

So I have to buy a new battery, probably this one: Varta Silver Dynamic G14 AGM 95Ah Start - Stop Car battery 595901085 NEW
https://www.ebay.co.uk/itm/Varta-Silver-Dynamic-G14-AGM-95Ah-Start-Stop-Car-battery-595901085-NEW-/361883445884

But there is another trouble, w running engine my multimeter indicates charging voltage of approximately 14,8-15.0 volts. The upper border limit showed at diagnostic is 14,85. Its 15 volts too high for charging/alternator output? The outer temperature now is around 40 - 50Fahrenheit (= 4 - 10 C)

I dont want to buy new battery and then to kill it by high recharging voltage. So:
- its 14,9-15.0 V to much?
- if yes, what I have to do? - replace the voltage regulator on the alternator?

Related

Need help with these codes (INPA) please!! https://www.m3post.com/forums/showthread.php?t=1785069

The DME adjusts the charging voltage per the age of the battery (old battery gets more voltage). When you install the new battery, make sure you code it in and the DME should adjust the voltage for the new battery.

ha9981 wrote

Related

Need help with these codes (INPA) please!! https://www.m3post.com/forums/showthread.php?t=1785069

My car has now 60k miles, no idea if the battery there is origin one or replaced one, but its OEM.

I have no codes at diagnostic, only the car showing me "increased battery discharge". I check it w multimeter and its really low. And also I check the voltage w running engine, ant its to high. But the car work normal, no "Christmas tree" on the dashboard (warning markers are not ON). So the question is if the higher voltage from alternator have to do something w low battery (alternator is trying to fully recharge it) or opposite the the nok alternator/regulator produce high voltage 15V and that makes the battery discharge.

Regarding registration of the battery, I checked the current old one inside the car and it wasnt registered. The voltage was 14,9-15,1, when I register it (it was only one icon for manage that), the voltage goes to 14,8-14,9. But right now the battery isnt fully charged, so maybe it can increase the voltage also. So I see as following:

1) charge the battery and check the output, if isnt 13 V w off engine and at least 800A, then isnt fully charged (probably reason is the battery is to old and I have to buy a new one)
2) after recharged battery/or installed new one check the voltage again and if the there will be 13,8-14,6V w running engine, than its ok
3) if still 15V appear, then next step is to replace regulator or alternator, but no idea how I should to know what is the correct way? I have no fault codes, only battery discharged, so no idea.

Is possible to buy separately regulator for 40 USD or complete alternator w regulator for 600, correct?

And finally its always there a possibility of some brokem/bad grounding cable somewhere (or this stuff cant issue higher charging voltage?)

Well, after recharge of the battery the voltage from alternator goes a little bit down, from 14,9 to 14,7. So I will check it from time to time, but it looks a battery condition affect the incoming voltage from alternator.

It is possible to replace the regulator separately as long as the slip rings are in good shape on the alternator.

I had an alternator fault code and replaced it, and the fault has been gone ever since. $60 for a brand new Valeo part vs 600+ for the alternator, worked out well. Definitely wasn't the most fun part to replace though as access behind the alternator is a bit tight.

Just make sure to register the battery and you should be good. Voltage shouldn't be exceeding 14.7 - normally when all things are working properly you'll be in the 13.9-14.4 range (this is on a car without MSA - MSA cars will behave slightly differently).

Also make sure u are using a battery charger that supports AGM batteries

BPMSport wrote

It is possible to replace the regulator separately as long as the slip rings are in good shape on the alternator.

I had an alternator fault code and replaced it, and the fault has been gone ever since. $60 for a brand new Valeo part vs 600+ for the alternator, worked out well. Definitely wasn't the most fun part to replace though as access behind the alternator is a bit tight.

Just make sure to register the battery and you should be good. Voltage shouldn't be exceeding 14.7 - normally when all things are working properly you'll be in the 13.9-14.4 range (this is on a car without MSA - MSA cars will behave slightly differently).

thanks, I have MSA (but I switch off this start&stop function). What is there a normal voltage range, 14,2-14,8? Which kind of regulator have you used?


Based on BMW there can be 2 variants of alternator numbers.

12317838656 is the EOM, produced by Valeo and used by BMW during car production, I didn't find any alternative product at bimmercat.com
https://www.fcpeuro.com/Parts/?keywords=12317838656

12317837981 is also OEM and BMW recommend this one for case of warranty replace of origin one, no idea why, but dealer told me because is cheaper. For this item I found interesting alternative from Valeo directly, for 280usd instead the BMW 545usd. I believe this Valeo have to be same as the OEM.
https://www.fcpeuro.com/products/bmw-180-amp-alternator-valeo-12317837981

Regarding regulator 12317847517, looks like there isnt any replacement at bimmercat.com but at threads there is recommended the second bellow Bosch
https://www.fcpeuro.com/Parts/?keywords=12317847517
https://www.ecstuning.com/b-bosch-pa...317561939~bos/

I can't imagine the misery of replacing the regulator, reinstalling, and only then realizing it's actually a bad alternator.

So perhaps a smart route would be to take it out and have an alternator rebuild place test it.

Is it available for any cheaper on RockAuto?

I would never consider the cost of a regulator replacement. The time and effort involved to stretch the life on a (8-10) year old alternator when a brand new alternator can be had for $280 doesn't add up.
As mentioned above. Valeo 12317837981

ha9981 wrote

I can't imagine the misery of replacing the regulator, reinstalling, and only then realizing it's actually a bad alternator.

So perhaps a smart route would be to take it out and have an alternator rebuild place test it.

Is it available for any cheaper on RockAuto?

Yes, I got alot of heat for purchasing through RockAuto and going the Valeo OE route, I think I paid $230. It was a brand new part and seemless transaction, quick delivery. It been a couple years, no issues.

https://www.rockauto.com/en/partsearch/?partnum=12317837981

InnerBlueSkies wrote

ha9981 wrote

I can't imagine the misery of replacing the regulator, reinstalling, and only then realizing it's actually a bad alternator.

So perhaps a smart route would be to take it out and have an alternator rebuild place test it.

Is it available for any cheaper on RockAuto?

Yes, I got alot of heat for purchasing through RockAuto and going the Valeo OE route, I think I paid $230. It was a brand new part and seemless transaction, quick delivery. It been a couple years, no issues.

https://www.rockauto.com/en/partsearch/?partnum=12317837981

Why heat for doing that? Sounds like a good price. Sure it's not lifetime warranty but most of us won't be able to own these cars for life.

ha9981 wrote

Why heat for doing that? Sounds like a good price. Sure it's not lifetime warranty but most of us won't be able to own these cars for life.

Mostly the OEM crowd. With few exceptions all my parts are OE through FCPEuro.

InnerBlueSkies wrote

Mostly the OEM crowd. With few exceptions all my parts are OE through FCPEuro.

FCPEuro is mostly aftermarket. I hope you're not paying FCP's prices for Genuine BMW. They are usually way more expensive than a good parts department.

And to be clear: I placed three orders with FCP *yesterday.* I'm not knocking them.

I also use Rockauto when it makes sense, although I will say that an alternator is *not* where I'd cut a few corners on price. Why? Because alternators these days are frequently garbage. I just swapped out a "new" Bosch alternator that lasted 18 months. Alternators are probably the least reliable replacement part out there, so FCP's lifetime exchange is *great.* Not to mention the ease and simplicity of buy it now, install the new one, and then just doing a return. None of this getting it approved ahead of time business that adds days to the process.

nrubenstein wrote

InnerBlueSkies wrote

Mostly the OEM crowd. With few exceptions all my parts are OE through FCPEuro.

FCPEuro is mostly aftermarket. I hope you're not paying FCP's prices for Genuine BMW. They are usually way more expensive than a good parts department.

And to be clear: I placed three orders with FCP *yesterday.* I'm not knocking them.

I also use Rockauto when it makes sense, although I will say that an alternator is *not* where I'd cut a few corners on price. Why? Because alternators these days are frequently garbage. I just swapped out a "new" Bosch alternator that lasted 18 months. Alternators are probably the least reliable replacement part out there, so FCP's lifetime exchange is *great.* Not to mention the ease and simplicity of buy it now, install the new one, and then just doing a return. None of this getting it approved ahead of time business that adds days to the process.

I think Valeo should be good. The option of paying an extra $50 at FCP should be considered. It's a 20% premium so I can see choosing either way.

Bosch has been dropping the ball a lot lately. A lot of complaints about new parts not working or failing prematurely.

On the topic of dealer being cheaper than FCP for Genuine BMW parts, which dealers? The ones online all seemed around the same price to me. But this info should be useful for me in the future.

The local dealers in Canada are usually more than FCP or any US dealer even with a 20% member discount.