Battery Issues / Voltage Regulator?

[JMunks]

Went to start the car the other day and it clicked, and no dice.

Figured it was the battery, went to Autozone, replaced it, and it started up beautifully.

However, the guy went to go and test the new battery and his device came back “Voltage Regulator Failed”

We also saw the voltage dropping from 13.5 to 13.2, and when I was driving it home,
at stop, it would get down to around 12.5.

I’ve scoured the forums and see some
mention of smart battery systems, but I’m not sure if that applies to my case here as to what’s going on.

Also don’t really wanna bring it to the shop and pay $200 just to find out it’s normal lol.

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[Farkel]

It's possible that the "voltage regulator failed" may be due to the tester not playing well with the car's battery management system, but I can't say for sure.
The voltage numbers you're seeing are normal for a fully charged battery. Remember, when the engine is running that number shows the alternator output, not the battery voltage.
After replacing the battery, you should reset the BMS to let the charging system know the battery is new - https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

 

[MiamiGT350]

I wouldn't worry about the "voltage regulator" error if the car is running and starting fine. Your issue was probably just needing a new battery.

You should execute a BMS reset:
https://www.mustang6g.com/forums/threads/bms-reset-no-tools-required.151602/

 

[ice445]

The PCM regulates alternator output only to what's necessary when the battery is a high enough state of charge (I think above 80%), so that's why you're seeing the low voltage with a fresh battery. Helps with efficiency.

 

[JMunks]

The PCM regulates alternator output only to what's necessary when the battery is a high enough state of charge (I think above 80%), so that's why you're seeing the low voltage with a fresh battery. Helps with efficiency.

Gotcha. Would that explain then the “failed” outcome on the autozone tester for the voltage regulator?

 

[WItoTX]

Gotcha. Would that explain then the “failed” outcome on the autozone tester for the voltage regulator?

I would be speculating how an AutoZone tester works. I'd say it's normal based on what you reported. Reset the BMS, if you haven't already, and I suspect it will be fine.

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