When I start my car my voltmeter hooked into the 12v ignition reads 14.4v for the first few minutes after starting the engine, eventually dropping to 13.8v. The voltage while driving will randomly drop from 13.8v all the way down to 12.5v, then eventually within about 10min later work its way back up to 13.8v over the course of 10-20sec. Only times I see the amp effect the voltage is when playing full tilt. Even then sometimes it'll be sitting at 12.5v, and then i play full tilt and the voltage does not move or go under 12.5v. Then still playing full tilt it will eventually work its way up to 13v. Often when the voltage is at 13.8 i play full tilt and the drop is to right at or around 13v. Although the voltmeter is on the ignition side, it is always within 0.1v if not dead on with readings on the back battery and amp at all playing volumes.
It's weird to be driving and see the voltage go from 13.8v to 12.5v. Even reving my rpm's has virtually no effect on boosting the voltage when its hovering around 12.5v.
Stock 120amp alty
Stock bat is in the trunk, connected to + on alty
Back battery (d3100) is hooked up to the + on the alty (only connected to front bat at alty + terminal).
1/0 with big 3, solid chassis ground.
any thoughts to why this voltage is fluctuating?