Ducati Monster Forum

I had an issue after a several hour ride, where I would hit the starter button and would either get one crank, then nothing, or it would crank a couple times and start like normal. I figured it had to be the starter button, solenoid, or other because I replaced the battery last August with a Yuasa AGM and it's been on the tender ever since.

A few days later when I went to load test it, it didn't have enough juice to start.

I left it on the tender overnight and it was up to 13.26v this morning. I disconnected the tender and let the battery rest for a few hours. It maintained the same reading over that time.

At key-on it drops to 12.65v, and at start it drops to 11.9v and goes back up. So load test appears good. It idles around 12.7v and goes a bit higher the longer it idles. In the 3-4k rpm range, it reads around 13.5v.

I believe these values are in the 'normal' range for an AGM battery. Can anyone confirm?

I don't run any accessories. Typically ride with the high beam on for visibility, which hasn't been an issue in the past.

Any thoughts on what might be causing this apparent discharge during riding or what steps to take to figure out why it happened?

3-phase or single phase charging system?

It's 3-phase.

I ran to get some gas in it and tested again after it had been running for a bit. It's starting fine with a full charge, as expected.  It idles right at 13v. With the high beam on, it drops below 13v. Holding rpm's steady at 2.5k, 3k and 4k it never gets above 13.58v.

Other posts I've come across indicate it should hit 14v and/or slightly above. I don't know if that's accurate for this bike, though.

Check AC voltage across the 3 alternator wires with them unhooked and engine running,  should be ~ 16VAC at idle and get to 100 VAC by 5-6k rpm

Thanks for the help. I'll give it a go here in a few. My multimeter and electrical skills are less than remedial at best.

If you've got a helper to twist the throttle a little and hold the connector while you check voltage, it's easier.

Finally got some time to dig into this.

The three yellow wires go to a plastic plug/coupling going to the RR that looks like it's able to be separated (plastic tab to depress).

I haven't had any luck disconnecting it.  [bang]

Finally got it disconnected. Fairly burnt inside but not horrible.

How does one extract the spade clips from the plastic housing?  I think a good clean could restore the connection but can't get to them with the plastic housing in the way.

Will test once clean.

Small screwdriver, press down a tab releases clip.

Thanks. Yes, looks like a plastic tab on the inside of the shroud. I finally got one out. The other two are being disagreeable.

Always amazes me how what should be a 15 minute jobs turns into 3 hours. Or more...

Anyone know a source for these connectors?

The male side is good, the female side is too toasted to salvage.

I cut the connector off and tested at the bare wires.  All three combo's were consistent:
1.1k rpm ~ 17VAC
5k rpm ~ 70VAC

Enough to suffice? Or totally no bueno?

Stator's fine.

Rick's Motorsport has connectors, Eastern Beaver too.

I've been toying with trying some of the connectors that the Electric RC folks use, they've got several sizes and they're gold plated and made for high current. No plastic shrouds, so it's a bit more DIY work.

Great. Thanks much.

Totally forgot about Eastern Beaver. This place was recommended over on ducati.ms, so I gave them a try:
http://www.cycleterminal.com

They've got a lot of stuff, that's cool!

I finally got all the parts, a good crimping tool, and some time.

I cut off both connectors, crimped on new terminals and new connectors. Still the same; idles right at 13V and never goes above ~13.6, regardless of RPM.

Any other thoughts or suggestions?  Time for a new R/R or could it possibly be something else?

13.6 is on the low side of good for an AGM battery, but 14 would be better, because the voltage take up of a battery is not 100% effecient. That effeciency drops as the battery is in decline.  If you pull the headlamp fuse what does the meter read? Correcting bad connections and parasitic losses could give you that 0.5V that tips the balance. Recheck all the usual culprits that corrode like case to cable and frame to cable contacts, tarnished cable lugs, battery terminals, etc to find that 0.5ish Volts. With your voltmeter, did you find a voltage difference between the battery - terminal reading and the frame or engine readings? I've lost track :)

There are probably more generous Regulators available if you can't find the "leak".

I'm not sure what you mean, can you please clarify?

Electrical is not my strong suit --I'm mostly fumbling about with guidance from multiple forums, youtube, etc.

Thanks!

Sorry mate, Sensei Howie would have described it better ;D

Put the positive prong of the meter to the positive of the battery and the neg prong to battery negative and note the voltage.
Then put the negative prong to the motor and note the voltage.
Then the neg prong to a frame bolt that cuts past frame paint and note the voltage.
Look for a voltage drop or barrier to a good earth. It can tell you a lot. Rusty bolts  lugs  etc that connect a neg earth lead to the frame or motor can block some of the voltage available.
There's a bolt to the motor near the case breather that could connect the earth pathway between motor and frame, and cable or cables from battery earth to frame. Howie will talk you through it or provide a link to a guide. We're looking for voltage barriers or "leaks" that stop all the available energy getting to the battery from the charging system. I'm using layman's terms to give you a mental picture of how bad connections prevent full flow of power from the alternator (via the regulator and cables) getting to the battery. Imagine its water.

Remember that paint is an earth barrier so motor case bolts and frame bolts that cut through paint into metal are best for testing with the negative prong.

With the voltmeter connected to the battery say for example you saw 13.5 volts, but only 13 volts when the negative prong is on the motor case, you would know that the earth cable lug to the motor case may need a good scrub or fresh bolt, cleaned case threads, etc. If only it were that easy.

So keep the positive prong on the positive battery terminal and move the negative prong to various negative earth points to see if the voltage drops. You might see zero volts at places of thick insulating paint. You can do this with the motor off at first to get a good idea.

Others more proficient in the art of electrickery will explain other more involved procedures.

Howie has, for quite a while linked to a video, https://www.youtube.com/watch?time_continue=132&v=_B0LjwQbUbg&feature=emb_logo  Much easier than doing all that typing.  Yes, it is for a car but it works for bikes too.  The drop could be on either positive or negative.  No drop you might consider a new regulator or keep your revs up at stops when a major consumer like high beam or heated clothing.

Hai Sensei  [thumbsup]

A picture paints a thousand words, a video even more.
Let us know how you go.

Thanks again, gents. I appreciate all the great info.

Time has been in short supply, but I should be able to poke around some more in the next few days.

 [beer]

With engine off, on at idle, or at 3.5k RPM, there is no drop in voltage touching various ground points including the at the back of the case where the ground wire is connected.

I also pulled the headlamp fuse to test. Of course it went flying and ended up in the plastics somewhere, so had unbutton the rest of the works to find it  [bang].  But fortunately located it. No lights at all brought it from ~13.6 at idle to ~13.7. No change at higher RPM's. I'm guessing this expected and not indicative of a loss?

So grounds appear to check out. The stator at ~70VAC seems to check out.

The other connector between the RR and the battery, on the RR side has 2 green wires and 2 red-white wires. On the battery side, 2 black and 2 red. I get 0 ohms between battery negative and each black wire and 0 ohms between battery positive and each red wire. If I'm actually doing it correctly, I understand that means I have continuity at least from that connector to the battery.

I'm not sure how, or even if it's meaningful to test the wires from the RR to the connecter. It's a short run and both sides of the connector look clean

I also did a 'bench test' using this video: https://www.youtube.com/watch?v=IzjVDL4ZtlE

All the diodes checked out.

I'm not sure what or how exactly to test anything else at this point.

Thanks again for the help, much appreciated.

I'm not quite sure how to attach to the circuit without disconnecting wires, which would break the circuit.

Which connectors are you talking about?  Also, which bike?

Unfortunately, except for the testing you did, there is really no conclusive test on a regulator except replacing it with a known good one.

It's '99 ST2.  The video you linked had a post on the alternator he connected to, then to the battery terminal with the other probe.  On the bike, there is no exposed post or wire on the alternator to connect the probe. So I'm not sure how to effectively test voltage drop.

We've established I'm getting proper juice to the RR. We've also established I'm not getting enough juice from the RR to the battery. I've also established (correctly, I think) that I have continuity in the last part of the run from the RR to battery.

I don't know if there's anything else I can effectively test, of if the above is sufficient to establish that the RR is at fault.

I didn't figure out a way to test the short run from the RR to the plug that then connects to the battery. I suspect that's not a likely culprit, though.