Odd Charging Behavior

[dostoy320]

Hey all,

I just installed a voltmeter on my '82 R65LS to try to get a sense of the charging system, since I'd been seeing some erratic numbers when just running a handheld unit to the battery and revving the bike on the stand. I'd often see ~9.7V at idle as well as up into the rev range after starting, but eventually I'd start getting 13.6 or 13.7V off idle up into the revs. In all cases, the generator light on the dash glows at idle and quickly goes off above 1000rpm.

The voltmeter I installed is wired straight to the terminals on the battery via a switched relay, all new wiring by me. Today I did a bit of riding around to monitor things. I'm really confused by the numbers I'm seeing.

Today's ride (almost new battery fully charged):
Key on, voltage reads about 12.6V.
On startup, the voltage dropped to ~9.7V.
I rode away, and the voltage stayed right around 9.7V, even off of idle up to 3 or 4000 RPM.
After about a minute of riding, the voltage suddenly came up to 13.7V while cruising.
After this, the voltage would always stay right around 13.7 off of idle all the way up the rev band.
When stopped at idle, the voltage would hang around 12.4, then suddenly fall back off to 9.7 after about 30 seconds.
Taking off again, the voltage would go right back up to 13.7, sometimes 13.8 or 13.9.
After about 30 minutes of stop and go riding around town, the behavior changed.
Same behavior at idle, holding 12-something then dropping off to 9-something, but off idle, it would max at 12.7 or 12.8 throughout the rev range.
It did this until I got home.

Any ideas to explain this behavior? It's obviously capable of charging and did so through most of the ride, but that low voltage at idle and the eventual drop to 12.7-ish off idle is confounding to me. Planning to order Jones' Classic Boxer Charging straight away.

Any ideas?

[Barry]

9.7 volts while cranking might be just about normal but not while idling.  For the voltage of a good fully charged battery to drop that low implies a huge current draw which only the starter or a short circuit could produce.

On the time taken for the voltage to rise to 13.7 volts, that could be classically interpreted as the rotor not being energised via the charge lamp and then suddenly the residual magnetism in the rotor kicks in at mid revs and charging commences.  And yet the charge lamp is behaving normally which would tend to rule out that theory.

There are all sorts of possibilities for the cause of intermittent charging behaviour such as dodgy brushes or intermittent faults in the rotor windings but this business about 9. 7 volts doesn't fit with such symptoms as a good battery would not drop that low under normal running power draw. For that reason and assuming you are confident of the voltmeter connections, I would investigate the possibility of short circuit somewhere.

[dostoy320]

Thank you, Barry. I'll hunt for a short circuit.

Edit to add:

If any of you LS folks are looking for a cheap, reliable voltmeter, these are very nearly a perfect fit for that cutout in the dash.
https://www.makerfocus.com/products/makerfocus-2pcs-mini-digital-dc-voltmeter-0-28-inch-two-wire-3-0v-30v-waterproof

I bought a two-pack of these years ago when I wanted to put a voltmeter on a Suzuki GS450 that fried a battery after a R/R failure. They are a solid block of epoxy and seem nearly indestructible. I recalled I had one left over in the electronics drawer and was pleased to find it is exactly the right fit vertically, and about 1.5mm too wide. I cut off the mounting tabs and used a file to bring the sides down just enough that it press-fits into the opening in the dash.

[Bob_Roller]

Rick Jones Boxer Cherging System is a very good book I recommend it to anyone that wants to learn the system .
One thing you could check pretty fast, take the bike out after it gets dark outside and see if the GEN light comes on dimly .
I had issues with the charging system on my '81 R65, couldn't figure it out until I worked a double shift got out at 11PM and saw the GEN light on very dim, couldn't see it in daylight   .
Worn brushes on the alternator .
Also you have a 45 year old motorcycle, let's face it not many people operate 45 year old vehicles !!
Most likey not the issue here, but corrosion on electrical connections is not uncommon .
One thing you mentioned about the voltage while using the starter, that is low, most likely a starter that is dry on lubrication .
Below 10 volts, can cause ignition system issues with the electronic ignition system .
There's a guide here in the R65 FAQ section second page on Bosch starter disassembly and lubrication .

I've done three starters so far the last two I went to a local starter, alternator, generator repair shop $50 each for rebuild lubriation, no parts replaced .

Motorrad Elektrik has a sercive to clean replace bushings and lubricate for $100 plus shipping charges .

[georgesgiralt]

Hi Lads,
I concur with Bob. The electrical harness on my bike was as stiff as a stick and the wires where black/green instead of the nice copper color one expect.
I measured the resistance for some of the wires and found several Ohms.
A new harness solved all issues the bike had.
And it is available and not that costly.
So if I where in your shoes....

[Tiedie]

Hey all,

I just installed a voltmeter on my '82 R65LS to try to get a sense of the charging system, since I'd been seeing some erratic numbers when just running a handheld unit to the battery and revving the bike on the stand. I'd often see ~9.7V at idle as well as up into the rev range after starting, but eventually I'd start getting 13.6 or 13.7V off idle up into the revs. In all cases, the generator light on the dash glows at idle and quickly goes off above 1000rpm.

The voltmeter I installed is wired straight to the terminals on the battery via a switched relay, all new wiring by me. Today I did a bit of riding around to monitor things. I'm really confused by the numbers I'm seeing.

Today's ride (almost new battery fully charged):
Key on, voltage reads about 12.6V.
On startup, the voltage dropped to ~9.7V.
I rode away, and the voltage stayed right around 9.7V, even off of idle up to 3 or 4000 RPM.
After about a minute of riding, the voltage suddenly came up to 13.7V while cruising.
After this, the voltage would always stay right around 13.7 off of idle all the way up the rev band.
When stopped at idle, the voltage would hang around 12.4, then suddenly fall back off to 9.7 after about 30 seconds.
Taking off again, the voltage would go right back up to 13.7, sometimes 13.8 or 13.9.
After about 30 minutes of stop and go riding around town, the behavior changed.
Same behavior at idle, holding 12-something then dropping off to 9-something, but off idle, it would max at 12.7 or 12.8 throughout the rev range.
It did this until I got home.

Any ideas to explain this behavior? It's obviously capable of charging and did so through most of the ride, but that low voltage at idle and the eventual drop to 12.7-ish off idle is confounding to me. Planning to order Jones' Classic Boxer Charging straight away.

Any ideas?

Well being a 84 LS rider owner that is currently installing the EME elictronic ignition, I'm replacing my altinator rotor and diod board also with all new wiring.
But my question is what do you have your idle set for? I have mine set low at 750 to 800 but the manual specifically states 1000 rpm for idle. Witch brings me to my problem which is high idle after warm/hot to the tune of 1200 to 1500 rps which is my bean can having sticky brushes and springs butthat's my problem.
Sorry for getting off topic. Try turning up your idle first thing then look for other problems if your gen. light goes off at 800 to 1000 which is normal idle settings. Maybe your low voltage readings will improve.
Good luck and if I can help reach out
David

[dostoy320]

Update: My issues were caused by a failed, almost-new battery.

I spent a quality evening going over connections, cleaning things up, looking for shorts. Time well spent.

Eventually I thought to shoehorn in a known good battery off another bike, and sure enough, the charging system behaved as expected, sticking right around 12.2V at idle and consistently climbing to 13.9 off of idle.

I just got back from having the battery tested and it is confirmed bad.

Tiedie: I have my idle set to right around 1000rpm after it warms up (it is about 800rpm on startup). My gen light goes off as soon as the needle lifts above 1k. Sorry to hear about your wandering idle issues!

[Tiedie]

Update: My issues were caused by a failed, almost-new battery.

I spent a quality evening going over connections, cleaning things up, looking for shorts. Time well spent.

Eventually I thought to shoehorn in a known good battery off another bike, and sure enough, the charging system behaved as expected, sticking right around 12.2V at idle and consistently climbing to 13.9 off of idle.

I just got back from having the battery tested and it is confirmed bad.

Tiedie: I have my idle set to right around 1000rpm after it warms up (it is about 800rpm on startup). My gen light goes off as soon as the needle lifts above 1k. Sorry to hear about your wandering idle issues!

.

Great news for you ! Yes I'm digging into it and sorting it out I'll let you all know when it back together and running.