Battery Voltage Draw

I just installed a Voltmeter / Distribution block.  I noticed when I start the car at idle the volts read around 13.5  or higher which is healthy.  After the headlights turn on , the heater turns on, and the stereo is fired up. my draw runs down to below 13 volts  (around 12.8 average) I'm only running 325 watt 4 channel amp, running off 8 guage wire with 60 amp fuse.  Do the volts seem to dip too low for my application?  I read another post which said after 12.6 amps your a taking from your battery instead of alternator. Also when the volume is up really high (bigger bass hits) the lights on the distro block dim. but the lights for the dash and headlights (alternator) don't budge at all.  'When the car is off the Voltmeter stays solid at 11.9 volts.

does this seem like a battery problem?  Also if I look at the electrolyte the color is YELLOW /GREEN instead of all green.  Does this always indicate  bad battery?

Thanks for help!!!

Doesn't fluctuate with the engine speed that much. mabye goes up .1 or .2 amps

are my numbers normal then?

Yes your numbers arn't that bad, considering you're running all of that stuff. This is kind of off subject but PAC makes a handy low battery indicator if you like to run your system when your car is off. battery saver

Thanks for the help. I feel better about my numbers now.  As far as a indicator.... My power inverter has a built in shut off protection for when my voltage gets too low.

So what would be the operating voltage (car running) when you should start getting problems 12.5 volts?

Just to ask again; 

What is safe operation voltage from my battery then?  Car running.  anything above 12.5?  or should I try to stay higher?

Thanks!

OK

So if my car is running with accessories cranking, and my voltmeter reads 12.8 then thats bad or good? or just ok. 

Because everything else I see reads around 13.5 with stuff running.

I'm just looking for alittle more detail.

Thanks for help