Don't know if this is the right place for this, if not I apologize so mods move to correct place if need be.

Lately I've been reading post's about adding extra batteries and people asking about charging systems. Which got me thinking about our RVC systems (regulated voltage control). Our cars don't always provide a constant 14.4v while running. Depending on inputs and certain preset factors our charging system can go as low as 12.8v while running. So when adding extra batteries isn't that not enough to provide an adequate charge to the extra battery? Also when looking at amplifier ratings they sometimes give ratings at 12.6v and 14.4v and the amount of watts at each voltage. So when cruising and the voltage is down to say 12.9 we are getting the lower wattage, is this correct?
Just thinking, maybe I have too much free time..

 

correct. All your non regulated amps (most of them) like rockford fosgate, kicker ect will have less power with less voltage. And the few regulated amps have the same power regardless but at lower voltage the pull more current... giving you a downward spiral once u reach those low voltages

Oh also remember that nice gm feature has the alt only give out 14.4 for the first few seconds when starting. Most of the time our cars sit at 13.8v

The lowest ive really seen a running car go is ~10v below that **** starts breaking (which ive seen too)