I have a probox with a kicker comp VR 10" and alpine 350W mono amp on it. I also have a small (around 200W) pioneer powering the front componet alpines.

Well at moderatly high levels, i'm getting some diming of the light in the instrument cluster, and at night i'm geeting a little head light dimming.

So do I really need a cap, or is there somthing else I can do! I think its 5 Ga wire from the batt. and like 8ga to each amp.

thanks for the help!

 

Yes, that or a bigger alternator. You can put a larger gauge wire on it and it isnt going to change the fact your alternator/battery cant meet the high momentary load your equipment is demanding. When this happens the voltage momentarily drops to maintain the current/amperage demand. Caps filter out these low voltage drops by applying stored potential.

 

Well, I kinda thought that, just wanted a second opinion before I go out and get a cap. I dont want to sink a whole lot of $$$ into one, Its not like i'm compeating or anything, but I'll prob. get a 0.5 fard unit.

anyone want to commont on that??

 

Its kind of a numbers game... You have to figure out how mach capacitance you need. But, if the problem is minor then I think a .5 will be fine.

If you want to know for sure how big of a cap you need, find out your base voltage, how current starved your amps are and for how long. Multiply those together and it will tell you how many farads you need. You will need an osciliscope to measure these things. That or go to the local shop and ask a tech who has a good 'feel' for guestimating cap size . The later will probably be the easiest by far. good luck.

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Oh and be very careful, the advantage a cap has to a battery is that it can discharge its electron store very fast. A charged cap of this size (.5f is a darn big cap...) can hurt you pretty good if you're not careful, so respect it .

 

You check the ground connection from the battery? From the looks of mine, there's only a tiny 8AWG wire tied to the chassis from the ground post. There's a slightly larger +12V power cable coming from the alt, and then there's 2 mongo power/ground cables running down to the starter. I didn't look at the starter to see how or if its ground is really tied to the chassis via a beefy connection or not. I assume not since the engine sort of floats on the chassis.

I don't have my system setup yet, but this seems like a weak link that's dirt cheep to fix instead of wasting $$ on a cap that you might not ever need.

 

didnt think of a puny ground connection. makes sense.

 

This is a very sensitive subject that has gotten a few bloody fists in this forum. The forum "longtimers" will tell you NO, you are wasting your money. I would take a look at that chassis/engine ground first. There are many studies that say cap's are not necessary - especially if you have decent quality amplifiers. Our trucks come with pretty hefty alternators. Lots of people here running over 1000W systems w/o a cap and having no side effects. My system is in the 750-800 range with no dimming with power windows, fan and system cranked...



If you are calculating the need for size of a cap, you also need to take into effect the efficiency of your amp and figure that if your amp is only 70%-80% efficient, that 20-30% of the incoming power is turned into heat and noise. When using power requirements, take this into effect, not the overall output of the unit. If not you may find your cap is NOT big enough, if you decide that is the best way to go.

Example, a sales person will tell you that you need .5farads for every 500Watts... Well, your amp may be a 350 watt, but it may draw 500 watts...

 

My 2 cents......A WASTE OF MONEY!!!

 

OK, I'm going to check the ground.

I've had many freinds with 700-100 watt systems, no cap, and no prob, thats why I posted.

I know the new f-150's come with AT LEAST a 100 amp alt, but I think most with power acc. like windows, seats (mine) have more like a 130 amp alt. It seems that would seem sufficent for my small scale system, like 600w MAX.

 

On my older 01 F150 I had two 1 farad caps, one on my highs one on my subs, and my lights still dimmed. I recently bought an 05 and did quite a system upgrade in the neighborhood of 1000 watts. I did not use a cap but i did change the size of my chasis ground to match that of my power (4 guage) and no dimming. Some may say that because ford went to a higher voltage generator vs an alternator that power output is greater. I personally have to agree with the oldtimers and increasing the chasis ground makes sense. But if you want a cap I have a 1 farad Rockford Phosgate digital readout for $60.00. Good Luck.
https://www.f150online.com/galleries....cfm?gnum=6456