1989 R100RT Charging Voltage and AC Ripple



Disclaimer: Before posting this, I looked into Snowbum's electrical articles to see if I could find the answer there. If it is, I missed it, sorry Bob!

Premise: I have installed a 600W Omega system on my '89 R100RT. This involves a higher output alternator, an adjustable regulator, and a much more robust diode board. I also installed an Odyssey 925L battery. After about 1000 miles on it, the system has given me no problems. Until I did a long trip to the Tail of the Dragon, with a total of 1200 miles, many of which on highways at 65-75 mph.

Here are the symptoms: Analog voltage gauge starts very low, less than 12, progressively moves up past 15 (red zone) and camps out there. On occasion, the needle goes erratic and pegs high. All this I initially attributed to a bad volt meter (they do fail, and this is 30+ years old...). Initially, I thought I might have set the VR too high.

In spite of this, the bike started every morning without issue, although one time, just after starting it, I used may horn and realized it wouldn't work with the bike at idle (voltage too low). Other than that, no apparent problems.

After I got home, I tested the volt gauge (off the bike) against a variable voltage source and noted that, while it reads a bit low around 12 volts, overall it tracks fine. Could it be that the bearing and dampening system are kaput?

I also tested the battery with two different testers, one of which also analyzes the charging system. Both told me the battery was OK, with a voltage in excess of 12.8 volts and more than 400 CCA (rating is 330). However, when I tested it again the following day, both told me the battery had less than 90 CCA and needed replacement (!). Without any charging in between, I tested it again today, and wouldn't you know it, both of them say it's a good battery. Cold started the bike and it started with no hesitation. However, the tester that checks the charging system also told me that the ripple is 1.3 volt.

I checked my other Airhead, which has an identical setup, and the ripple is around 0.4 volt.

1. What should the ripple be? In other words, what is an acceptable value? 0.4 seems already a bit high, but maybe OK, 1.3 sounds excessive to me, but I'm no expert.
2. If the ripple is excessive, what can I do to smooth it out? (Change Voltage Regulator? Change Diode Board? Add a capacitor somewhere?)
3. Has anyone else experienced these weird symptoms? (Erratic voltage gauge and difficult to assess battery health)

Thanks for any input,