2004 Chevy Tahoe (voltage drop issues)

[Jcd81381]

I had a stock 125 amp alternator on my chevy tahoe running my car audio system. Uograded to a 300 amp (off-brand) and Mechman 400 amp. Now im having more voltage drop than I had with my stock 125 amp alternator. Ive checked all connections and everything is good. Only thing i can think is the new alternators arent hooked up correctly. Car audio system consists of ...

*Alpine Halo 9 ilx-f309 headunit

*Underground Power battery delete 

*Underground Power 40ah lithium

*JY Power 40ah lithium 

*Sundown Audio Salt 3 amps (X 4)

*Sundown Audio Ns v5 d2 subs (X 2)

* custom Sundown Audio sub box

*1/0 power wire (4 runs)

*1/0 ground wire 

Any thoughts and/or help would be greatly appreciated. 

 

[killerc998]

Have you tried with just one of the alts hooked up. How are the alts wired? External regulator or internal? Any belt slipping?

[Jcd81381]

Yes, each alt starts the vehicle. The 300 amp is ran off factory harness. The 400 mechman is tapped into the factory harness, 1 wire ran to ignition wire (in fuse box), 1 wire ran to charging post. When i start the vehicle the voltmeters read 14.9-15 volts. When theres a deep, long bass rhythm section, the voltmeters go into "LO", and the amps cut off. Spl Labs Bassmeter registering 145-147 dbs at voltage drop issues. No serpentine belt slip. Thabks for your response and information. 

[killerc998]

Are you running 2 runs of 1/0 power to every amp, and 1 run of ground? Looks like you need more grounds. You have 4 amps running to 2 grounds.  Amps are pulling more power now then previous, and are probably looking for more ground. Wonder if amps are going in to protect.  I would add grounds and recheck.