And just to complicate it more, lol
Alternator's rating is with engine at 1,800RPMs not at idle, 750RPMs
At idle an alternator is only capable of 60% of its rating
130amp alternator would have about 80amps at idle
Which is fine
Most vehicles with all the lights on, engine running, heater fan on High might draw maybe 40amps, so 80 to 90amp alternators were what most car makers put in as stock
That gave enough "head room" for constant power window up and down, and cycling power door locks all you want, lol
130amp alternator would give you 40 amps to use at idle
Cooling fan may draw up to 30amp when they START UP, but that will drop down to under 20amps once they are running
I can't see light bars drawing more than 20amps unless you are running Air Craft Landing lights, lol
LEDs are brighter and draw less amp so that would be the go to in my opinion
Sound systems are a different story
Sound watts are different than electrical watts, so any watt/amp calculation should then be multiplied by 0.7 to get the actual electrical amps needed, and as said thats at FULL VOLUME
And sound watts can be misleading
2 watts is not twice as loud as 1 watt
10watts is twice as loud as 1 watt
So its a factor of 10
Most vehicles have a 40 to 60watt system, 10 to 15watts on 4 channels, which is VERY LOUD
To get twice as loud you need 400 to 600watts, i.e. times 10
Low frequencies need the most "power"/wattage, a 200watt powered sub-woofer would rattle the windows in a vehicle with a stock sound system
As said the sub-woofer draws the most AMPs in the system and especially when it hits a low "note"
You can get capacitors that install on the 12volt wire to the powered sub-woofer
Capacitors are like mini batteries, when the sub-woofer hits a low note the capacitors provide that brief extra voltage needed so alternator doesn't need to
As said the Battery is not used at all when engine is running, battery's sole purpose is to start the engine, period
Battery voltage is at most 13.0volts, usually 12.5volts
Working Alternator's lowest voltage output is 13.5volts, average 14.0volts
So voltage flows TO the battery when engine is running, keeping it charged up, never from the battery, if so Battery light will come on and there is a problem in the charging system