Highway Headlight Dimming

[5thgenaccord 10+ year member]

I just recently added a new amp and my headlights go nuts on the highway at 70mph. I have a 94 Accord with 2 yellow tops 700 ish cca, 1 farad cap, and a new alternator that puts out 90 amps. I am running 2 grounds on the underhood battery (4ga and oem). The rear battery I am running 0 ga ground. I am running a 4 ga from underhood battery to alternator. From my understanding of a capacitor, it holds temperary voltage to be used and regenerated quickly. So now that I am running 2 batteries and would have more avalible voltage, would adding a bigger cap help headlight dimming? I really don't want to replace the alternator because the one I have is new. I was also told by a car audio specialist that if I got a high output alternator I would run lean (it could have been just that type of alternator).

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[Prowler573 5,000+ posts]

The only thing in your car that creates voltage is your alternator. All the batteries do is provide you with storage banks for that voltage to reside in until it is called upon by the car, the stereo, etc.

Your capacitor is likely causing you more harm than good - it is merely a storage bank as well and makes one more thing for the alternator to have to charge.

A better upgrade would be to upgrade the "Big 3" of your underhood wiring. For a very complete tutorial on what I mean have a read here.

Upgrading the Big 3 does in no way increase the charging capacity of your car. The only component that can accomplish that is going with a bigger output alternator. However, increasing the cable size on the Big 3 will provide for a much more efficient path for the existing current to flow upon.

It's widely accepted knowledge around this forum as well as most other online car audio discussion boards that capacitors are a marketing trap and a waste of money. There's good reason why you don't see the biggest names on the competition circuits using them in their setups.

 

[Chevyaudio 5,000+ posts]

X2 on what prowler said...

Ditch the capacitor, its probably doing more harm than good

Do the big 3, it will help

But ultimatly a 90 amp alternator is small. I recently upgraded from my factory 105 amp to a HO 240 amp and it cured all of my dimming problems