+1 bad battery. Either that or you improperly wired your amps and they don't cut off with your radio.

If your car runs your alternator is fine.

 

So where does the power to charge the capacitor come from? Caps are only effective for very brief or very fast current transients, and after that they become a load like everything else. And, they're a very low resistance load at that, so they draw power very fast to charge themselves up. Caps really do nothing at all with bass heavy music because of this.

 

I don't even look at watts anymore... I rate an amp typically by looking at the fuses. Add them up and you have your maximum load.

 

That's like estimating the power of an engine from the size of the exhaust tip and the number of stickers on the body.
You're assuming a lot about their fuse ratings... You should never reach that maximum fused load anyway or else you're really abusing the amp. The fuses tell you absolutely nothing, because you shouldn't be approaching that point at all. Continuous wattage is the only way to go, because you'll have lots of peaks above that point and lots of time below that point.

 

I was having the same problem a few days ago. My lights would dim and if I left the lights on for a couple minutes the car would crank real slow. I had the battery checked and sure enough the battery was bad. I replaced it with an 80 dollar battery from Advance and everything works fine(no dimming or slow cranking). I didn't want to pay 200 dollars for a battery but the Autocraft Titanium works perfect for me and I have a 4 channel and a mono amp hooked up definetly running at least 650 watts RMS with stock alternator and no capacitor.

To Fabrik... I don't mean to thread jack but everything seems to be fine with my car. I can tell you know what you are talking about. Should I get a cap or anything to prolong the life of my battery? Will I have any problems in the near future?

 

Well if a car had a 1" tailpipe, you know that it couldn't have 1000hp even though the sticker on the side says it I'm just saying I use the fuse rating because unless reputable, I don't typically believe the numbers stated. RMS can always be stated higher with the sacrifiace of distortion.

 

A cap isn't going to prolong the life of the battery, batteries just age and the lead grid plates break under mechanical strain and vibration over time. As long as you're not consuming power faster than you can replenish it with the alternator, you'll be fine. So for example, you don't want to be draw a continuous 50 amps with the amplifiers and only give back 30 with the alternator because you'll be draining the battery. You can buy another battery or more for the price of a cap.

A cap can sometimes help with dimming but that's about all it does. Amps have enough bulk input capacitance that they often don't have much use for a big external cap unless they are at the end of a long wire run.

Conversely, you have no idea that the car is only 125 HP even though it has a 4" exhaust. This what happens sometimes when you go with the fuse ratings.

You really have no idea of what the amp puts out though, because you don't have any way to accurately measure it. So whether you believe the marketing hype or not, you don't have any way to know if it is true or not. You certainly can't tell with your ears, or how "hard it hits" (I hate that phrase). So yes, if you're sizing everything downstream to be able to handle the max possible current that the amp can draw, fuse ratings would work. You're just never going to be reaching those current levels, and you have no idea how much headroom is build into those fuse ratings, so no matter what you're just guessing.

Also, see above post on the non-existence of RMS power.

 

Explain your impulses. I'm just saying, I noticed a difference from wiring up the dvc subs in my last car. First, I wired them up in a series-parallel configuration and it made my lights dim really bad and even droppped my engine rpms a little bit when the bass would get intense. When I wired them up in just the parallel config, I didn't really experience a heavy current drain like I did with the previous setup. System was basically: Kicker Class D 750W and 2 RF HX2's. Not much, but enough to tell a difference. Plus that;s just another suggestion besides ten people saying "battery"...I think the guy got the clue after the first one.

 

So you just randomly hook things up until you figure out what makes your lights stop dimming? I can tell you exactly what will draw the most current: the lowest impedance load to the amp. Anything in parallel will lower impedance, and raise current but also raise distortion. Anything in series will raise impedance, lower current draw, and lower distortion. You should be wiring up subs according to what load the amp will be best for distortion and efficiency, and should get the type and quantity of subs based on that. Just randomly messing around with different configurations doesn't get you anywhere, that's what spec sheets are for. There is no guessing necessary, everything that you have described is in the spec sheet, and all of those things are governed by the standard laws, P=IV, V=IR, etc.

You have an awfully risky method of setting up electronics, I hope you don't do any engine swaps or tuning

 

Randomly hook things up?... nah. I just wanted to see the difference for myself. I don't see how that's a risky method if I could care less about the subs or amp. I knew what I was doing and just wanted to see for myself instead of looking at spec sheets or going by word of mouth. Plus, when a project gets to the point where I don't feel comfortable, yes I will ask for help...aka learning.