going to be putting a pretty big amp in my car...


5 Year Member
Oct 8, 2009
i have it from my last car...its a 2400w amp...ive already installed a 200amp alternator...question is i also have a 5 farad capacitor...ive heard some ppl say use them and some say dont...do i need it?

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i got 2 rockford p3s in the trunk with a 850 rms amp and i had to use a cap just so my lights wouldnt flash but i think its smarter to put a 2nd battary in the trunk save on power but i also had a few other tings running off one battary tho!
I would go for a second battery, capacitors are just bandaid fixes, there is still strain on your electrical system, battery and alternator, you just don't see it because the amp is pulling the stored power from the capacitor, I literally just read a write up from jl audio about using capacitors and after reading it I will never use a capacitor, If I can find it I will post it up for you.
I am putting one 12 inch kicker comp cvr in my car this weekend along with a kicker 500.1 mono amp so I too will be upgrading my charge system, but no capacitor.

I am most likely going to get an optima yellow top and a 140 amp alternator and run 4 gauge wires.
dude, you have a 200 amp alt. i think your going to be ok honestly. maybe use an optima with it as well.

i have a 130 amp alt in my fox. i run 2 amps. one is 600 rms one is 500 rms. i listen to nothing but heavy/fast bass. i can be sitting at a light with my fan on, high beams on, heater on second notch and the music cranked and it holds fine for me.

i dont know how anyone could handle more wattage then similar setup to me.. the noise reflects off my rear windows and it is LOUD at 1100 rms. i have pushed any/everyone out of the car with discomfort at 20-22 on my deck of 40 volume notches.

anyway, good luck. i have no capacitor, just a red top optima and 130 amp alt.
I would (and am) just replace your alternator to battery wire with at least 4 gauge, also do the engine to chassis and battery to chassis ground with 4 gauge wire, and run the red or yellow optima battery, I am picking up my yellow top tomorrow, or just find a good deep cycle battery, didn't see that you have a 200 amp alternator so you should be good there, what alternator is it, some alternators will advertise a certain amp but not tell you that it only puts out that much amps at a high rpm, making it no better than the stocker.
I have seen dozens of systems ranging from 250-4000 watts and none of them have ever had to run a capacitor. If you listen to music where it only hits hard for short intervals you may be fine with a capacitor but take the same system and put on something that hits hard for long periods and your alternator still won't be able to keep your lights from flashing while it tries to charge your battery and capacitor.
i have a 0 gauge wire running from the amp to the battery...(monster cable)...actually i found a guy on the forum i got the amp through...great kit and price...unit work awesome...my stock battery is dead now so i do need a new one...yellow top or red top optima?

thanks again guys :nice:
ive also read/heard that the yellow top is much more forgiving. guy at my work had 2 optima red top's go dead and they were ruined. i had a yellow top in my fox years ago, i drained it so many times and it never quit.

my car came with a red top so ill replace it when needed.
i have it from my last car...its a 2400w amp...ive already installed a 200amp alternator...question is i also have a 5 farad capacitor...ive heard some ppl say use them and some say dont...do i need it?

Very quick electrical tidbit. Volts * amp = power.

So a 200 amp alternator at 12 volts can only put out 2400 watts.

The car itself prop needs 90 amps to run (fans, PCM, fuel pump, ignition, lights) that leaves 110 amps for "other stuff". 110*12=1320 watts of reserve power.

Once your 2400 watt amp uses up the available 1300 watts of alternator power, any additional power has to come from the battery.

Any battery discharging at a 100 amp rate is not going to last long before discharging. Once the battery is dead, there is no power to excite the alternator field coil. No battery=no output from the alternator.

A 200 amp alternator is not big enough to run a 2400 watt sound system full out and handle the car's electrical loads at the same time. In fact, the alternator is not big enough to power just the amp (at max power).

So if you are actually planning on running your 2400 watt amp full out, you need a cap and a 2nd battery. I do not think that a bigger alternator is possible.

Note, an amp is not 100 percent efficient. It takes more power in to get "x" amount of audio power out. Therefore, a 2400 watt amp will need more than 2400 watts of power. Again, this is at max volume level.
yeah i will be running it about half...so probably be using abot 1100-1200 watts most of the time...no way i could handle it full out all the time...lol...but just want to make sure i should def use the capacitor. thanks for the info...its very much appreciated. :nice: