will i need to upgrade the alternator or will a big 3 upgrade be sufficient with the following setup: Vehicle- 2007 Chevy 2500HD with dual batteries (factory) Amp- US AMPS MD1D 1200W RMS (@ 14.4) Class D
I tested the volts at idle with a fluke multimeter w/o the amp hooked up and factory stereo playing. The volts coming out of the alt was around 14.4 and the amps coming out of the primary battery was about 14.2 and the amps out of the secondary battery was lower at about 13.6.
"I'm not sure about your particular truck but most chevy HD trucks have a 140 amp alternator." Just keep an eye for extreme voltage drop and light dim. It most likely has a large case efficient alternator but the idle amperage more than likely won't be over 80 amps. You should be fine running that system on there but just make sure you use caution if you notice anything.