need advice, dimming problem

hey all, maybe someone out there can give me some ideas here. im having a dimming headlight/dash light issue, kinda annoying. ill post all the wiring and gear below. incase i forget to include what brand things are, its all rockford fosgate except for the waveguides.....

big 3 upgrade-0/1 wire(fosgate)

new battery-xs power 3400new alt-250 amp

1x rf power 1500bd amp for 2 12" rf power hx2 subs running@ 2 ohm(birth sheet shows 1724 rms@2 ohm)

1x rf power 550x amp(birth sheet shows 724 rms@2 ohm) for a set of usd audio waveguides on front 2 channels(i believe they are 8 ohm) and a set of rf fanatic q components on rear 2 channels(4 ohm)1x rf power 250m amp(dont have birth sheet) for a set of rf 6.75" he subs in front kicks(2 ohm)1x rf 25 farad carbon cap(maybe useless from what ive been reading lol)

as for the wiring, all fosgate....

0/1 gauge from battery to cap then 4 gauge from cap to distro block then 4 gauge to amps

0/1 gauge rear chasis in rear to cap then 4 gauge to distro block then 4 gauge to amps

i also have an audio control eqs which i may have to much boost in some areas as i dont have access to an RTA, every shop i know wants to charge an arm and a leg to do it....rediculous

any ideas or help will greatly be appreciated

So you only have one battery? That's the first problem. It's a deep cycle battery. That's the 2nd problem. Is the cap on the light circuit? That's where it should be to prevent dimming lights (unless you move the AGM battery adjacent to the amps in which case mount the cap with the battery (to protect the battery)), but your case is one of insufficient power distribution.

wow i didnt think upgrading my factory battery to the deep cycle would be an issue here. what are you reffering to the cap being on the light circuit?

To stop headlights dipping, a cap can be used across the light supply though as I have often written, a battery is better (even if a 1.2AH AGM etc). But you also have dash light dimming and that's a separate circuit. If a single main battery is used with big audio, then it's usually a cranking battery since they can supply a higher current better (and without less damage to the battery - especially if it's an AGM). And if your alternator is big enough, then there is no need for a deep cycle unless you want to run the audio with the engine off (ie, alternator not operating). But big audio systems are usually multi-battery installations - namely a normal cranking main battery, and then audio batteries (usually) located with the amps connected to the main battery/alternator via a battery isolator. That provides the local surge reserve for burps as well as ensuring cranking independence should the amp battery run too low. The audio batteries can be deep cycle if a long reserve time is desired, though cranking batteries are better for surging amp draws. In secondary audio battery systems, caps are only used to protect AGM batteries from high surge currents, but that is only relevant for systems above 2-3kW output (assuming normal large sized AGMs). But even then, an extra battery is a better solution. IE - it doesn't take a large battery to beat even a 25F cap (1.2AH should be more than enough) but the extra battery(s) is to reduce the surge on a single AGM, hence usually 2 (or more) matched batteries. Long term paralleling of multiple audio batteries should be avoided, but they could be manually isolated if unused for long periods (ie, for days etc). If high power audio is not required without then engine running, the main battery isolator could be used as a master control for separate relays - ie, between the main/cranking battery and audio battery, and relays between that audio battery and each of the other audio batteries.    Of course the inter-audio-battery relays can have a manual switch to parallel them when the main isolator is off.

well i did forget to mention....i did have, as you stated, a 2 battery set up before this. i had the xs power 3400 and a xs power 975 with the battery isolator. i had to remove the xs 975 due to it had a swelling issue and i didnt want it blowing up under the hood. removed the isolator as well.....but while  i did have the 2 battery/isolator setup, i still had dim issues. i do know that dodge has that can-bus crap(which mine has). could that have anything to do with this issue? i have a digital volt gauge on the driver a pillar which never drops below 14.1 even on heavy bass/music but the lights are dimming. i took a reading at the rf 1500bd amp and it was showing 14.15 volts

What is the voltage when charging at the main battery? It should not exceed 14.4V long term (unless specs (Optima LOL) say different). Overcharging kill AGM batteries and can cause swelling. However the swollen AGM may have had a collapsed cell etc. Refit the isolator. One bad battery brings down the other. And for AGMs, thermal runaway can occur (selling, heat & BANG!). The 2nd battery should show the same voltage as the main battery when connected, less any voltage drop due to its load. But of course that drop should be minimal.

i figured maybe since the 2 batteries where of different sizes, maybe thats why i had the swelling issue on the smaller battery. i had the smaller battery as the cranking/starting battery and the big one as the 2nd for stereo and what not

No, the swelling has nothing to do with battery size. And when charging, battery differences are irrelevant (assuming they are both 12V lead acid - ie, wet cell or AGM - and not failed). Only when batteries are left connected in parallel when not in use (charging or supplying a load) are mismatches a problem. But that is not size related - it is terminal voltage and self discharge (profile) related. In short, long-term or permanently connected batteries should be matched and symmetrically connected (ie, equal +ve & -ve interconnects, and for 2 batteries with +ve out from one battery and -ve out from the other). However that is academic in most automotive situations since the batteries are not collocated (hence different temperatures) and have differing loads and current paths, hence becoming more unmatched as time progresses.    Besides which, even 2 matched batteries left permanently paralleled and unchecked means double the failure rate with both batteries being lost (ie, you replace 4 batteries in the time you'd normally replace just one from its statistical "self failure" failure rate). Even shorter, that's why battery isolators are used. Hence because batteries are isolated when NOT being charged, their size, capacity, charge profile, history etc become irrelevant (except in cases of cell failure). Batteries can be paralleled when charging, but otherwise only as required - eg, to provide extra capacity for a load.

well like i said, i had an 500amp isolator for the batteries and the thing swelled....took to auto store for them to dispose of. maybe my amp gains are up to far too?

The isolator did not cause the swelling. In fact, if not for the isolator, it could easily have turned into a fire. Think about it. When an isolator is not active, the 2 batteries are isolated. Are you saying the battery swelled just sitting there, or when connected to a non-charging alternator? When an isolator is activated (ie, when the alternator is charging), the 2 batteries are connected and it's the same as a direct link without an isolator. Do you think it more likely that that's when battery swelling occurred? If the latter, then either the alternator is overcharging (its voltage is too high), or the swollen battery had a failed cell or cells. If it's failed cells/s, then if it's still connected to the other battery when not being charged... And since an AGM battery can supply more current than a 250A alternator (not that it would into a not too failed battery) and itself heat up... ie thermal runaway of both AGMs. Get an isolator, else manually disconnect the 2nd battery when not being used and check its temperature (heat meaning high discharge or charge rate, or a fully charged or faulty battery).