2007 Honda Civic voltage drop down

I have installed a voltage stabilizer + voltage reader + ground wire + 1200w audio amplifier + 3.0 farad capacitor + xenon light, everything was good but now I removed the xenon light and changed the battery.

while stopping in a traffic light, everytime when the A/C compressor works the car lights dim, and when I turn the fan to full speed and the headlight and fog light on the voltage drop to 11.9 - 12.1 and the car RPM goes below the average and I feel the car will shutdown, but when I move the voltage goes up to 13.4 - 13.6.

in the morning when I start the car the voltage reader gives 13.8 - 13.9 but when I start the A/C its gives 13.6 and when the compressor start it goes to 12.9 and then goes to 13.5, when its off its return to 13.6.


any sulotion for the dim? If I change the ground wire it will help? Or my battery ( amp hour - 20 HR RATE) 45. If I change it to 60 Amp h?

i need help please.