Replaced a shorted-cell battery in a friend's truck yesterday and went looking for reasons why it might have failed (other than the usual team of Age and Heat).

Charging circuit was putting out a nominal 13.6VDC but also 30VAC (p-p, so roughly 20rms). This seems a lot but I checked 3 other vehicles and they _all_ had ~30VAC ripple - so I have to gather that's "normal".

Is it? I've never seen a spec for AC ripple. I know that diodes either short (bad scene - coil wires remain energized...) or open - causing lots of ripple - but what's 'normal' ?

I havn't seen a spec either, but being there are no CAPS in the charging circuit, (other than the battery sort of) i would guess that to be normal. I do know Chrysler does kinda bump charge, using an AC spike to keep the battery from sulfating.