OK well my electrical system is VERY stable now. Voltage at the battery while the engine is running never changes. It's the same at idle, or revving the engine. This is a great improvement!

However, I noticed something. Even with perfect, large, well-conducting cables connecting the battery to the alternator, the voltage at the battery terminals is always 13.8v, not 14v or higher.

I think this is fine, because now, it doesn't sag down to 12v or lower at idle, like it used to, it stays solid.

I actually was just reading about AGM batteries (which is what I have) and it says that the best charging voltage for them is 2.3v per cell, which comes to 13.8v, so this is actually good. It says 14v or higher can degrade the lifetime of the battery.

Just for your information though, if anybody wanted to maintain at least 14v all the time (for example, maybe for car audio amplifiers or something where that makes a difference), you can do that.

I used to have a Zener diode wired inline between the alternator sense wire and battery positive. This bumped up my output voltage to about 14.5v, and with the smaller pulley, it stayed that high all the time, even at idle with the fan on, headlights on, and other electric accessories.

I took the zener diode out though because 13.8v is plenty.

There does seem to be some drop in voltage though, probably due to crappy wiring, at the cigarette lighter. I only see around 13.4v at the cigarette lighter. I think that's OK though.

Main thing is, now my alternator can maintain high enough voltage at idle to keep the battery charged even under heavier electrical load <img src="/forums/images/graemlins/kewl.gif" alt="" />