Voltage too high, bass amp goes into protect

[Ajf23]

i currently have a 2003 Expedition, with a “PCM controlled alternator” meaning voltage is controlled by pcm I don’t know how to better word that.
I have a 360 amp high output alternator, big 3, and xs power d6400 for electrical, and a taramps md3k for bass and a skar 4x400 for mids and highs (I don’t remember the model) for a total of around 3500 watts.
While on the expressway, my rpm’s sit around 2000, and the alternator pulley is a 3:1. So I know my amperage is right around 300x14.5=4350watts which is more than enough to run the system.
But the problem I’m having, is running the system at full tilt on the expressway my voltage hangs around 13.3-16.6ish. And it keeps sending my bass amp into protect. I tuned it with a multimeter to push just a hair over 3k, and the clip light on the amp only flashes when it’s like a drum never for the long notes. I’m kind of stumped on why it jumps to 16+ and how to get it to stop.
Regular driving around without music it stays between 14.7 and 15.1, on the eway it settles to 14.9.
I was thinking about setting up a second xs power d6400, and grounding to the frame, but that’s like $800 after all is said and done, and I would hate for it to not fix the problem. Also, it would in my mind only fix the problem after the second battery and everything before it would still see 16+ volts which is borderline terrifying.
Any help/insight is appreciated
Thank you in advance for your time and knowledge.






Edit: spelling

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[2023 LTZ]

I recently discovered a bad connection causing a similar issue. My voltage regulator measures from the negative and has its own lead. The big 3 was removed off a vehicle I wrecked and reused on current vehicle of the same vintage. When I originally crimped this lead to the 0ga something wasn’t right causing it to overcharge. I was able to trick it but for 2 yrs I swore all connections were solid.
Fortunately I remade a new negative and use a ring terminal for that lead giving me 13.6-13.8 after about a minute of starting.

 

[Ajf23]

I recently discovered a bad connection causing a similar issue. My voltage regulator measures from the negative and has its own lead. The big 3 was removed off a vehicle I wrecked and reused on current vehicle of the same vintage. When I originally crimped this lead to the 0ga something wasn’t right causing it to overcharge. I was able to trick it but for 2 yrs I swore all connections were solid.
Fortunately I remade a new negative and use a ring terminal for that lead giving me 13.6-13.8 after about a minute of starting.

I will check the connections on my car again, I do have an extra run of 0 guage with ring terminals on it, out of the same wiring kit the rest of the big3 is done with.

I’ve recently noticed as well my abs light flashes on heavy notes, and my “check charging system” light is consistently on. If it’s a super heavy note the light will shut off and turn back on.

 

[2023 LTZ]

16 is pretty high. Check continuity on your existing stuff before redoing it.

 

[Popwarhomie 5,000+ posts]

16.6 is way too high. That will destroy an AGM battery.

What alternator brand did you use? Sounds like a voltage regulator issue.

Are you using the stock alternator plug or did you wire it yourself bypassing the OEM plug?

On my Scion TC that is PCM controlled I did not use the factory alternator plug at all.