Low battery voltage constant with revs

[Yamaniac]

Gen 2 AS (/AE). Battery terminals measure 13.5 V to 13.6 V from idle to 5000 revs ish. No additional load.

By all accounts this is a low figure and should go up above the 14V mark. Suspecting something like bad connections, or lost one of the phases.

Why so constant though? Whatever's failing wouldn't the output improve with revs? It's like the regulation is working too well.

The regulated voltage is fixed isn't it, so it can't be an adjustment thing?

Cheers

 

[lnewlf]

how old is the battery ?....old batteries have higher resistance....do the headlights get brighter when revs are brought up?

 

[RossKean]

Check the resting voltage of the battery - ignition off after allowing the battery to "rest" a couple of hours to dissipate surface charge.  If less than 12.5 V, there is a good chance the battery is the issue.  Even if the battery has sufficient voltage, have it load tested as well.  It might have sufficient voltage and even the total capacity might be OK but a load test may identify internal resistance issues which could be a signal that it is going off.  (as per Inewlf's post, above)   I have never had over 14V at the battery terminals while engine was running...

When you have some time, read the following thread started by dcarver.  It specifically addresses your issue with a verified solution.  But check the battery first.

 

[mcatrophy]

Possibly bad connections between the rectifier/regulator and the battery. The RR measures the voltage at the unit itself, so doesn't "know" about any voltage drop between it and the battery. Since the bike's load is constant regardless of engine RPM, the 1/2 volt or so drop through any resistance would be constant. Can you put additional load on? Main beam headlights take a little more than dipped, might show a bit more voltage drop. If your bike is fitted with a passing switch, this puts on the main beams leaving the dipped still on, this would be a more significant increase in load. If there's no significant change in voltage, then my suggestion is wrong.

Some people have reported corrosion at the RR connector, might be worth investigating .

I presume you've checked that the battery terminals are clean and tight.

 

[RossKean]

Not much difference in current draw between low beam and high beam - depends on manufacturer but more a difference of geometry than power.  Let the bike idle until the fans come on and see what happens.  That would be a more significant change in total current demand.  If you have heated gear or grips, turning these on max should give you additional draw as well. 

As per mcatrophy, make sure connections are all good (at RR and battery).  And check out the dcarver thread I linked.

Note: I wouldn't be especially worried unless voltage while running down the road drops below 13.2 or so and stays there or continues to drop further.  If you are below that, you may be running into a deficit situation and the battery will gradually become discharged.  

(Have you checked the calibration of your voltmeter???)

 

[philter]

Wow, thanks for this post. I had no idea my 8500 would display voltage. Yes it is a little lower than my voltmeter reads at the battery, but knowing that it's all about change. Sweet. I call this a coronavirus benefit. LOL

 

[mcatrophy]

Not much difference in current draw between low beam and high beam - depends on manufacturer but more a difference of geometry than power.  Let the bike idle until the fans come on and see what happens.  That would be a more significant change in total current demand.  If you have heated gear or grips, turning these on max should give you additional draw as well. 

Yes, not much difference in the current between the two headlamp settings, something around 0.7 amps or so. Just trying to think of an easy way to increase current draw. Your idea of fans is much better, but make sure you rev the engine to 3 or 4000 when you take the measurement, at idle it almost certainly would drop voltage even on a perfect system.

 

[Yamaniac]

Thanks people.

Latest findings/measurements:

Before starting, battery = 12.7 V. This is on a battery I just swapped in, after taking it off my other bike* months ago and just leaving it on the shelf. Replaces a Shido L ion. No difference between them, apart from Shido still had 13.3 Volts after itself being left standing for months. Was wondering if the good reading on a neglected battery meant my DVM was reading high, but the problem's more in line with a low reading DVM. Will measure the other bike as a comparison soon.

Started fine, first go.

Idle = 13.5 V, 5000 RPM = 13.6 V

With beams on and heated grips at max heat: Idle = 13.3 V, 5000 RPM = 13.6 V (Not sure if I’ve got a passing switch. Didn’t want to annoy the neighbours leaving engine running ‘till fan came on, probably do that tomorrow.)

Noticed rapid flickering when at idle on those sidelight things and the LCD cluster. Maybe uneven voltage from losing some of the stator windings or something? Or maybe it’s normal?

Have another problem that I didn’t want to get mixed in, but wondering if they’re related. It’s the yellow light + Sh__37 one. Has happened occasionally throughout the two years I’ve had the bike. If you’re lucky it sulks for 10 minutes, then you can start it and carry on fine (have to keep switching on, checking if error still displayed, switching off and trying again a minute later). Last time was not so good though, had to come back to it hours later after thumbing a lift home. Felt confident it would re-start after that long and it did. That was last July, didn’t want a repeat so been laid up since then.

Am thinking the issues might be related after reading the Sh__37 error’s description in the manual - ‘Power supply to clutch or shift actuator motor is abnormal’. Have my doubts though, seems like some folks pile on the current draw with heated vests and such ‘till their voltage is below mine, with no seeming shifting problems. Could be that none of them are on an AS(/AE) I guess.

Got quite a few hits on here searching for general Sh_*, but only a couple for specific Sh__37. Didn’t seem to be any magic bullet that definitively fixed things, but lots of suggestions to try.

The idea was to tackle the charging and eliminate that from the equation (assuming there is a problem). Then take it from there.

As a first step towards fixing either problem will just start stripping down and poking around following the suggestions - cleaning connectors, measuring voltages etc…

Sorry for verbal diarrhea - I get carried away.

* Sorry guys, but it’s an old Ducati Multistrada, who’d have thought that would end up being the reliable one.

 

[rbentnail]

Everything you describe voltage-wise seems to me to be perfectly normal.  My bike is now on it's 3rd different battery and has exhibited the "symptoms" you describe since new in Jan 2008.  I think you may be overthinking it.