Alt or batt?

Let me try to explain my situation the best I can.... I own a 2000 silverado.5.3l. I have installed a stereo sony cdx780 head unit, with 4 volt pre out, and a kicker amp ix402. Running 8 gauge wire from the battery to the amp, fused 12" from the battery.Grounded to the chassis 18" fro the amp. Running 2-12" bostons, the amp is bridged. I have a stock battery 600cca and 300 Load test? Stock alt,putting out 105 amps. I am having voltage drops.I can see the voltage gauge in the truck drop and go down. when i leave the truck sit for a long period of time the voltage is up, as i drive and play the stereo it drops low and lights dim. And the amp is unable to get the required current and sounds different. I have done a test on the alt and it is putting out 14.4-14.5, 100% working, now my battery is at 70% not running and drops slowly when the stereo is playing(hard)which it is going to do !. So what do i need to do? I can upgrade the alt to 145 from 105. I am wondering why such the voltage drops?. Could it be that my alt is slipping on the pulley when the load is put on it or when it gets warm would it give out,or is it able to handle the amp draw, or is my battery so low that the alt doesn't have time to replace the used voltage.? What should I do? replace the battery with a new one? and what type, size. And if i just upgrade the alt would it help the battery(stock) that is in it work better? When i decide to do something I will also upgrade the grounds and power wires to better handle the draw from the amp.I am stuck at a spot where i have no idea what to do. I know everything costs money, however I want resolve the problem i am tired of wondering what to do. Does anyone have or had this issue and what resolved it?..


Bluebowtie

need a bigger battery, or two to keep up with the power your sound system is pulling. Its like adding lights or a winch, you need to compensate for the draw, and your alt can't keep up.

bigger alternator will help most. Dual batteries will be neccessary if you sit with radio jamming (ie tailgating). You might also try adding capacitors for the amps so when bass hits it will pull juice from them first, not directly from battery. Most likely what happens is with the volume up the system pulls juice straight from the battery via the amp. The stock alternator is unable to replace this extra draw as well as supply the trucks other needs think lights, fuel pump, ignition. The end result is a slow drain on the battery with continued use.

Start with a bigger alternator and better power and ground wires also make sure you have clean connections and good in line fuses for a system pulling this much power. This should help with your complaints. I would also suggest checking into the capacitors as this will help with sound quality and take some strain of the alternator. Then if you choose to upgrade stereo or add additional accessaries a nice dual battery setup would be the trick. unfortunately, dual batteries aren't alot of help if alternator can't keep up so start with that.

The caps mentioned are stiffening caps. Planning my system and going through the same thing right now. I agree with what has already been said, just wanted to clarify the stiffening caps thing. my two cents

correct.They offer a momentary source of aditional voltage (think battery) during a hard bass hit etc... that causes the amp to draw additional current or perform poorly.

correct.They offer a momentary source of aditional voltage (think battery) during a hard bass hit etc... that causes the amp to draw additional current or perform poorly.

Regardless of how many batteries you have the power has to come via the alternator. If you are drawing more than the 105 A the alternator can produce under ideal conditions the battery will be drawn down. Actually the battery is essentially not even being used while you are driving down the road as the alternator is supplying the current and keeping the battery carged in the process. The capacators can only supply current for a short period of time and then you are back to the alternator.

amps draw from the battery if installed correctly. That is why the large gauge power wire should lead to the positive post on the battery. You are correct in as far as ultimately the alternator is the weak link as it has to maintain the battery as well as supply the vehicles electrical needs when running. The short (momentary burst) from a capacitor is just that a short burst to the amp to offset the demand on the battery and alternator.

Bluebowtie,
Bottom line to answer the question, replace the alternator, this will also help in the future if you decide to upgrade your system. Get the caps as soon as you can, 500,000 uF for every 500 watts. This is what should probably be in your system already. The Caps will store the energy long enough to give your Battery a chance to recharge a little while the vehicle is running and the higher output alternator will help with maintaning the electrical demands of your vehicle and system.

It sounds like we are all saying the same thing, The alternator must be strong enough to maintain the battery and electrical while running, and the caps are staged energy for the Amp. The caps draw energy from the alternator while the vehicle is running, and the battery when not running.

I would recommend checking out a few sites like Crutchfield for one just to get some info on what is happening with your system and why you should do certain things. If you are really the inquisitive type you may want to grab a cup of whatever at one of the mega-book stores and sart reading through the car stereo mags and rags to get the answers to your questions from the pro's.

I am an amature at this and may stand to be corrected, however I am confident in what I have said. Again we all seem to be saying the same thing, but the answer doesn't seem to be coming out that obvious for bluebowtie