Help with Charging problem (stuck at 12.3 volts)

[Controller]

Now here is my story;

I have a 18'' fi btl sub and a 4000watt amp being powered by 5 batteries (one up front and 4 in the cab)

I recently had to change the batteries because they all started going bad (just really old, no problems that i know of)

The first batteries i had were cheap 650 crank amp used car batteries, and the new ones i just bought are 4 Red Top Ultima 1000 crank amp batteries and one normal interstate up under the hood.

My problem is this;

As soon as i connected all the new batteries (positives to positives & negatives to negatives), the voltage is like stuck at 12.3 and will not go any higher, almost like its capped out

The voltage drops to 11.8 when i slam the sub hard, in tern cutting out the amp since it doesn't get the power it wants.

However the altenator charges it back up to 12.3 VERY fast so i dont think the alt is bad

Yes all the batteries are connected to the front battery which is connected to the alternator, which is 100 amp. (not that high i know but it is after market and worked fine for 4 years charging 5 batteries constantly, and even though its getting kinda old, it still charges fine)

My Question is;

What is the problem that is causing my voltage to be stuck at 12.3 even though they are all brand new batteries (and all good), and how can i fix this.

PLEASE help.

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[daboyfrumdabx 10+ year member]

Just an FYI, there are much better options in batteries for audio purposes than Red Tops. If you had to stick with Optima, then the Yellow Top would have been a better choice.

I would disconnect the batteries from each other and measure their resting voltages individually to see if you find any large discrepancy with any of them. Furthermore, 4K on a 100A alt just isn't going to work. You'd be better off selling a few batts and buying a proper alt.

 

[Controller]

i understand 100amp isnt big enough, but it got the job done when i had my old batteries in

is it possible that the change in bat types caused the voltage lock up?

as for the batteries, i got the 1000 crank amp red tops at 125 a piece so i thought it was a good deal. all brand new

but what would you recommend i get, if i get all batteries from interstate at dealer prices (minus about 20% on every battery type)

 

[Controller]

never mind it was a bad zero gauge running from the front to back, and a bad ground in the back. two simple, but nearly impossible things to fine, took 26 hours to find/fix lol

thanks for the help though guys