rpm’s drop when car is in idle

recently i installed a punch500s and a kicker l5 in my car. i have a 03 galant.  a day or two after i noticed that every time i stopped at a red light my rpm's would drop really low, and my car would even turn off. i have a 1 farad cap, and a yellow top dry cell optima battery. what can i do to make this problem stop? anyones help is greatly appreciated.

brian

What size power and ground cable are you using?

That amp should use about 36 amps at full power. Your alternator puts out 90 amps (auto transmission) or 75 amps (manual transmission). Now are you running any aftermarket accessories? Also turn off everything except the engine like your lights ac etc and let me know if the rpms still drop. One ore thing do they drop at low volumes middle or high?

If you get a smaller pulley it might solve the problem. But if you do that then it will generate more heat and possibly shorten the life of the alternator. What is happening is your alternator will only put out its full load at higher rpms. So if your car idles between 800-1000 rpms you might only be getting half of the current as you would at a higher rpm.  So by getting a smaller pulley you are making the alternator spin faster and it will generate more current at a low rpm. Now if your going to swap out the pulley you should just do it right. Replace it with a high out put alternator that is built to put its max current at a low rpm.