The new battery is fitted. I also decided to go back to a rectifier and Zener setup. Simplicity, and easy on the stator. I verified that the Zener was cutting in at over 14 volts.
Went for a 300 mile ride on Sunday. When I left, my voltmeter was reading slightly over 13 volts at speed, but over to course of the day, it continuously lost charge until it was struggling to put up 12 volts at 4000 RPM. Battery voltage was 11.4 at idle. All readings are with the headlight on.
I did notice that the charging system would catch up if I switched from the headlight to the pilot light, although very slowly. I verified that the draw from the LED headlight bulb is 2.2 amps max, less than half of that of a halogen bulb.
I have verified the current draw of my bike, alternator disconnected. At a 1000-1500 RPM idle, it draws about 4.5-4.7 amps with the headlight on and 2.6 amps with all lamps off. There is no draw on the battery with the key off. So my maximum power requirement to keep up with the loads at 13 volts plus is about 61 watts.
I am beginning to wonder if I either have weak rotor magnets in my alternator, or I have a lot of resistance across my rectifier. I have tried 3 different rectifier/regulator set ups, and all have shown the same results.
According to Alton's specs, the alternator should be capable of putting out 90 watts at "cruising speed". I consider cruising speed to be between 3500-4000 RPM, which means that my charging system should be able to keep up, as that is where I spend most of my time while riding.
Thoughts??