Tigr

Hi guys. My BMW E60 had a problem with Alternator Voltage Regulator. it was not charging first 10-30 minutes. Then starting to work. When charging, it was starting with 14,7V and going down to 13,9 V - 14.0 V.

So my cars original BMW alternator is VALEO TG17C010. I bought VALEO Voltage Regulator and replaced the old one. I also took out the battery from the car and charged it at home with low current over the night.

In this period the weather got cold: close to 0 deg Celsius. So the alternator is giving now ~15.0 V and going down to 14,5V.

Guys, is this normal? Please help!

Loose-c-Cannon

Seems too high to me... Believe the alt should put out no more then about 14.1 roughly.

FormerE30Owner

What type of battery do you have and how old is it. FLA batteries will take 15 v charging if that is what the BMW smart battery monitor deems is necessary. The fluctuations you are seeing look normal with a FLA battery and cold conditions.

Salut, Bob P.

abe76247

"smart" charging strategies like E60 uses have temp based charge voltage. Colder batteries will tolerate, and need, higher voltage to reach full charge. That voltage level is normal for colder temps that you likely have where you are. The ambient temp is on the network for use by the cluster, climate system, DME, and any other system. My E60 and the last several company cars I have had all will go to upper 14's and even to as high as 15.3 when weather is cold for a time. They all drop in 30 minutes to lower 14's. I have a radar detector that I selected voltmeter as a screen filler when there are no alerts. I watch charge voltage regularly as a result. The detector reading agrees with my Fluke DVOM's.

BimmerFan52

The most important factor will be the battery SoC you start with.

If a battery in good health (and after sitting idle several hours so surface charge is gone) measures 12.6V+, then after starting the system voltage shouldn't stay above 14.5V for more than a short time until the battery charge is replenished from starting.

But if after several short trips the battery voltage starts low, then the DME may signal the VR to set a system voltage on the higher side until the battery is fully charged.

For an FLA battery if the IBS is working properly it will pass data to the DME which will signal the VR to lower system voltage once the acid temperature reaches 120degF to prevent excessive loss of water.

However, if sulfation has already impacted the battery's ability to reach a full charge and the ambient temperature is low, then the SoC will really never reach 12.6V+ and the acid temperature will rise slowly in the cold so higher system voltage could last an extended period.

I would suggest you remove the battery and fully charge it. Then immediately transport it to an auto store for a battery test. If the battery is in good health and withstands a discharge test well then you may need to look back to the alternator to ensure it is working properly.

Overcharging will kill batteries in short order.

Tigr

Thanks guys!!!

I have L5D 95 Ah / 950A(EN) 12 V battery from 2013.

I took out the battery from the car and brought it home. Charged it over night with BOSCH C7 charger in the regeneration mode. After some time from the disconnection from the charger the voltage was around 12,5 V. I Installed it back into the car (still 12,5 V).
Turned ignition on: voltage drop to 11,3 V - 11,6 V at this point. Turned on the engine, and the charging voltage came up to 14,1 V immediately and never got higher than that value.

So, I guess, the 14,9 charging Voltage was 1) or due to the cold battery 2) or due to badly charged battery. Will control again tomorrow morning, when the battery will be cold again...

Thank you, guys, again!!!

Tigr

Today in the morning, with only 1 deg Celsius outside, the alternator started to give 14,3 V only. Never went up to 14,9V. This means that the alternator is fine, just my battery was not fully recovered from the discharge... And probably it is not yet fully recovered. I will do another regeneration charge tonight.

FormerE30Owner

Actually that looks close to normal for a fully charged battery. I wouldn't do a recharge, but just continue monitoring.

Salut, Bob P.

cmyachtie

Assuming your E60 has an AGM battery those charging voltages are OK.
Flooded batteries should get a lower charging voltage.

BimmerFan52

Other way around. FLA can stand higher charging voltages (15.5V+).
AGM should not be exposed to a voltage higher than 14.8V.