Battery Charging Issues

[fel0ncod3]

Hi all, I've been trolling the forums, ross-tech wiki's, Facebook groups, and have called a few repair shops to see if they can offer any hint at what could be wrong.

Having a problem with the charging system.

History - Had the voltage regulator changed since it killed my battery. Same day, went to auto zone and got my battery replaced under warranty since it was shot.

Fast forward only a month into the future and I noticed that my battery meter (I enabled it via Vag), is saying that my battery is not 100% charged. As I drive during my commute, it teases and it goes back towards 100%. If I turn on the AC / Accessories, it doesn't seem to charge the battery and if anything it seems to drop the voltage!

I checked the back of the alternator and it is putting out... at 13.6 - 14.0+ (I checked over a few minutes). At the battery posts, it only says 12.7 - 12.8. I also checked for an amp draw and it's behaving normally at 0.009A after 3-4 minutes of locking the doors (and tricking the trunk closed). Reason why I checked for an amp draw is that a few nights ago, on my drive home, my battery went back up to 100%, in the AM, it was two ticks lower, maybe 80%?

Looks like it's not the alternator / voltage regulator... could it be the wiring?

Anyone want to chime in? Getting stumped the more I think about it.

[A4B8ueg]

By any chance did you leave your Ross Tech device plugged into the port?


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[Mina08]

has the copper wheel worn out on your alternator?
what year is your car?

[SDF1]

Please do not use that battery meter that you enabled.
Go to VCDS and check how many AH are left in the battery.

Also when your car is OFF, your battery hovering around 12.8V is good. With the car ON it should be between 13.8 and 14.4V (Depending on what you have running)

[Crucible35]

You do realize that when you apply a load to the battery (like turning on your AC) your voltage will drop based on that load, right? When the car is running your alternator is in charge mode and the voltage you are seeing is the charge voltage (13.6v - 14.4) which is normal for a 12v battery. I don't see anything all that abnormal from what you have mentioned above. Except that you didn't provide much detail as to what battery you put in your car. It's been stated a few times in this forum that the battery needs to be coded to the car after replacement. Although some say it doesn't. For battery meters to provide any accuracy, the meter needs to recognize whether there were any changes. Since many of these meters rely on historical performance, if you change any variables, the metering can be off. Example, if you previously had a 92ampH AGM battery in and replaced with 100ampH battery, when the charge from the alternator reaches 92ampH the meter may state that you are 100% charged yet you still have a way to go. Lots of variables.