I could use some help here. Some readings or experience would be very nice.

I took the 750 LS replica to a Ducati dealership in Oregon to list it on consignment. As part of that process they do a safety check. Their tech got "very high" readings on the charging output that day. They were: 15.9 DCV at high (6000) RPM, from 14.0 at idle. The ACV test, at the stator wires, read as high as 160 V at 6,000RPM, up from 70 V at 2000, and that really worried them.

I brought the bike back home, and quickly found the big red main wire from the positive side of the battery was loose! After tightening that, charging is now at 14 to 14.4 DCV at the battery from idle to over 6000 RPM. It reads 14.2 DCV at 5000 RPM (top gear, going down the highway). But, the ACV tests are still at 160 yellow to yellow, and 80 red to both (2) yellows. The stator is not grounded out. Nothing (except the engine) heats up. Adding a ground wire to the regulator body makes no difference. The stator wire resistances measure 1.5 Ohm Y to Y and .8 R to Ys, and that does seem high. It seems to be charging perfectly; for two days in a row. But now the dealership is getting shaky --- about having no tech info on an old bike, and the responsibilities after selling it --- or, maybe about my skills.

As some help/backup I started testing my F1. It has had only two batteries in 12 years, and no electrical issues. The first battery (Odyssey) lasted seven years, and the current one (same) is now five years old. If I don't ride it for a few months it needs a small/quick charge, and then it is fine for weeks after. It reads 13+ to 16 DCV charging over similar RPM range, and 15.6 DCV at 5000 RPM. And, it read 130/60 using the ACV test. Wire resistances are .8 to .6 Ohm same tests, just a tad high. I took it to three trackdays this year, turned over an indicated 10000 RPM more than once, and no drama. The wires ends from the stator look really sad now, and you can hardly tell what color they are. I will probably not change anything.

Any good experience or current testing would be helpful. Thanks, MikeV

The charge voltages you are showing are in the normal range. Most all regulators are set to about 13.8 to 14.5 volts in a 12 volt system. The charge voltage will vary depending on the electrical load and battery condition. If your battery is old and partly sulfated the regulator will sense a higher load, [resistance] and charge at a higher rate up to its upper voltage cut limit. Problems start when the voltage is over about 15 volts constantly and the battery will get really hot and boil the electrolyte or warp the plates. I think you have a non problem other than the loose positive cable which you corrected. Italian bikes usually have the opposite problem, low or no charging voltage! You may for peace of mind check the regulator leads for tightness or corrosion just to be sure.

Thanks Dietz.

I have decided it is charging just fine --- 13.7 to 14.4 DCV --- five different days. Sure is hard to get printed info on the specs for these two-wire alternators though.

MikeV

Maybe reviving this old thread can help answer my question(s).

I spliced into the alternator output wires on my F1 to replace as much of the dry-rotted insulation (inner wires) as possible with new. I never bothered to check output before (because it was charging fine as far a I knew), but I recently checked voltage at the battery to ensure the splice works and measured 14.9v a week ago and more than 15v two days ago.

Before I get in too deep:

1 - Does it matter how the two yellow alternator wires are connected to the rectifier/regulator? Which is to say, can they be reversed without causing any issues? I am reasonably certain that I put everything back as original, but maybe not. I wanted to ask before trying swapping the yellow output wires to see if there is a difference. Alternator theory suggests it should not make a difference, but I am not an F1 expert.

2 - More than 15v is much too high at the battery, right?

3 - If I need to replace the rectifier/regulator, can anyone recommend a replacement?

Thanks!
d

I have never paid any attention to where the two or three yellow wires go; it makes no diff.
My F1 has been producing 15.5V with headlight on for over 17 years, and blown a fuse one time. I have seen 16V on occasion. Even after taking it to track days and redlining it all day it never cared. The LS replica had all new alt and reg components, and it did the same thing, and the reg stayed cool. This caused some hand-wringing at the Duc dealer that had it on consignment, because they had no info on the old stuff and were comparing it to the new bikes. Bruce Myer told them “they all did that”. Personally, I would not worry about 15V. Or, you could go on the internet and really get some wide opinions about this. MikeV


PS: the first Shorai lithium ion battery went seven or eight years, and the second went longer. That in spite of whatever Shorai said about charging. But the reason I went to the Shorai was to get the 230 CCA, instead of the weak 180 of the original wet-cell battery. It really makes starting much easier. Plus they are light, and can be mounted in any fashion.

Thanks, Mike. That helps greatly—as opposed to trying to glean advice from Tha Internetz. I was going to pose the question on one of the FB groups but thought I might get a more succinct and accurate answer here first.

As long as the battery does not boil, I will not worry.
d

Mike, Of course i just bought a new battery but it was a normal sealed type that was mounted on its side in the back. Not an original. What Shorai model did you get?

Jeff

On my F1 there is now an LFX14A1-BS12, with 210 CCA. On the two bikes with 900 engines there are LFX18L1-BS12 batteries, with 270 CCA. Both batteries are the same small size, one just has more umpfh! The one on the TT900SS has been there eight+ years and is still reading 13.25 volts. MikeV

I think the Odyssey was 230 CCA, but it was bigger, heavier and, I think, had to be upright. The Shorai can be mounted in any position. I know there are even more choices, but we tend to stay with what works well.