So I have a 2001 denali with a stock alternator. I've done "the big 3" with 1/0 stinger wire, I have a stinger sp1500 batt in the stock location and I just added a stinger sp1800 battery in the back. Everything is wired with 1/0 stinger wire and I have a 40 farad cap! System is 1750 watts rms and when I turn it up loud( say 25 out of 40) my headlights dim even while I'm driving on the freeway. I've had my alt tested and its putting out 145 amps. Do I really need a third battery? I had a beetle with a bigger system(2600 watts) with the same batts, cap, wire combo but it had a 125 amp alt and had no probs with dimming. What do you think?
