Why still have electricity problems?

Hello, I have at the moment “nichtmal” 1kW at my plant (Zeus VII at 8ohm bridge and ne Signat RAM3 Mark II at the FS), I put plenty of thick cables (35mm2) and also took quality (Sicherungshalter is e.g. an ANL from Earthquake). Battery is ne Maxxima in the engine compartment. However, I still have extreme light flicker. It wasn’t that bad even with my old car with the Crossfire VR4000d (at 1Ohm!). What could this be about? Would a cap be the only solution? MfG, Di ddy