I’m running a 320 AMP alternator with a 44mm pulley, all 1/0 100% copper cables with hydraulic crimped copper lugs. Big 3 upgrade. I’ve got two Yellow Top Optimas wired in parallel and an external regulator setup.
The sound system includes two 12” T1s on a T1500 amp. The amp is grounded to the body and powered by the second battery. Alternator power goes to the primary battery. Both batteries and the alternator are grounded to the body.
At idle, I have a steady 14.5+ volts, but as soon as the bass hits, the voltage drops, and my lights dim. When cruising, it’s fine. What am I missing here?
Is the voltage on your first battery under the hood below what the alternator is putting out? That can stress the system. You’ve upgraded everything, so it’s worth checking. By the way, what’s the first battery? Is it stock? You mentioned a second battery—when did the issue start? After adding the second battery or upgrading the alternator?
@Mai
Your alternator should keep a minimum of 12.6VDC, or the batteries will start discharging. Are your connections clean? No frayed wires? Poor wiring could be an issue. Try grounding the alternator bracket to the same frame location you’re using for your main ground.
@Morgan
I’ve grounded the alternator casing with 1/0 100% copper welding cable, the same cable I use throughout the car. All connections are new with crimped copper lugs.
Mai said: @Morgan
I’ve grounded the alternator casing with 1/0 100% copper welding cable, the same cable I use throughout the car. All connections are new with crimped copper lugs.
Man, have you tried better batteries that supply more consistent voltage?
@Mai
When you’re testing, make sure to account for all electrical loads like lights, AC, and anything else running while driving. That way, your voltage numbers reflect real-world conditions.
@Finley
I had the alternator dyno-tested after the build. It hit my target of 300+ amps, but I didn’t check the idle output. I even asked for a smaller pulley before leaving to improve low-rpm performance. I figured it would hold 14.5+ at idle with the system running moderately, but the lights still dim at idle. That doesn’t seem right.
@Mai
Somebody mentioned checking the alternator’s output curve. Knowing the amps it produces at idle versus higher RPMs would help. Honestly, 12.5 or above at idle isn’t bad.