It doesn't have to cross the zero axis to have an A/C component. The fact that it was changing indicates an A/C component to some degree, but this is irrelevant. The fact that it tracks the engine rpm makes me think that one (or more) rectifier diodes went bad and let one phase drop out (or more). Guess we'll never know but I was curious. Thanks.

 

it's 2.1V per lead acid cell at full charge. 7 cells would be 14.7V your alternator voltage would have to be bumped to at least 15.7-16Vto be effective as a primary power source in the car.....great for the audio stream, horrible for anything else electronic in your car.

 

So if you were to leave the voltage regulator at 14.6, the battery would only charge to let's say, 85%, what is the problem with that?
There wouldn't be as large a gap between battery and alternator, and not bad for the electronics.

 

a lead acid battery ahs to sit at 100% charge to have any kind of longevity nless it's a deep cycle battery, Also with that little of a voltage gap between alternator and battery you'd be puling from the battery partially with every voltage dip causing it lose charge.

You'd fighting the fight to zero... you'd always just be fighting to ke the battery topped up.

also your alternator charges at 14.4 with minimal or no load. usually under any kind of load it's 13.8V.