Charging voltage

[Guest]

I have always felt that it is important to know that the bike is properly charging so this is one of the first things I check when I pick up a new ride. For ongoing monitoring, I like to mount a voltage meter. An early warning device as it were.

I fitted a voltage meter to the GS in December but didn't get to test it under load until last Sunday's ride. I noticed a couple of things that concern me as they are not what I've been used to with the Yammies I've owned.

Firstly, when the bike is started on choke and allowed to rev to 3000 or so the meter needle swings to charge but only hovers around 11 volts. When the choke is reduced and revs drop to 2000/2500 the needle bobs up to about 13.5v. when the revs drop to idle the needle hovers around 11/11.5 volts.

Secondly, when riding and accelerating the needle swings to the charge side but seldoms goes past 11.5 to 12 volts. When using the turn signals the needle swings in time with the flasher from about 10.5 volts to 12 v. That is normal I believe so no worries there.

I'm wondering if these readings are normal or should I be expecting a charging failure? I'm used to seeing the Yammies show charging at 13+ volts with engine revs over 2500rpm and under acceleration.

The GS has about 13K miles on it but it sat for the last 7 years and I have only put about 350 miles on it since resurrection at the end of the summer. Everything is stock and unmolested and all other electricals function correctly.

As always, I appreciate any input.

Cheers all,
Spyug.

[Steve]

Methinks you have a problem. :shock:

Voltage before you start the bike should be about 12.5 or so.
While the button is pushed and the starter is turning it might go as low as 10, but should not go lower.
Idling could be anywhere from 12 to 14.
Anything above 2000 rpm should show 14 to 15 volts.
Turn signal operation might make the voltage flicker a bit, but not down to 10.5.

Sounds like you might have at least a basic knowledge of electricity and maybe even a multimeter, so it's time to go through The Stator Papers.

Something else that caught my eye:

when the bike is started on choke and allowed to rev to 3000 or so

makes me shudder to think of a cold engine running that fast so soon. I have found the minimum amount of choke that can be applied to enable starting the engine easily, but keep the revs down to 1500 or so.

Oh, and you shouldn't be "expecting a charging failure"...dude, you already have one.


.

[bonanzadave]

Good news - It may just be a dirty R/R connector. Mine was. Never a bad idea to do the contact cleaner routine to every connector on the bike and the R/R ground wire jumper to the battery neg terminal.

Bad news - Your R/R & Stator are shot.

[spyug]

Steve,
Thanks for the reply. I wanted to clarify a point or two. The readings you get with an analog voltage meter are not terribly accurate so I'm not overly concerned with the values other than the 13+ charging voltage only appearing at 2000/2500 revs. In my experience it should rise to this level at any revs over 2500 so when it doesn't achieve it at 3000+ but does when it drops to 2500 again I begin to wonder.These findings are abnormal and I was looking for confirmation which you provided.

I am familiar with charging systems having rebuilt/ repaired 3 in the last 4 years. I do know how to read an electrical schematic and how to use a multimeter so I will be delving into the charging mods shortly.

On the matter of starting on choke and revving to 3000 rpm this is not my normal procedure and only done to test the charging above that 2500 mark and only for a few seconds. At the time of testing, the bike had been started and run for perhaps 10 minutes and was only on choke to allow me freedom to check charging at the battery with my multimeter. I have always been taught to start any carb fitted vehicle with the lowest amount of choke applied and to keep revs down as low as possible 'til the beast is warmed up. I try not to abuse my vehicles and equipment.

Appreciate your input.
cheers,
Spyug.

[spyug]

Bonanzadave,
Thanks for the input. Terminal and connector cleaning is also something I usually do right off with a new to me bike. This time I was so antsy to get riding that I didn't get it done. Winter , of course, is the best time for this fiddly stuff so she'll be back on the lift and I'll be poking proding and cleaning the crud from all connectors I can find...starting with the R/R block.

I'll report back in due course.

Here's hoping I don't have any pooched parts.

Spyug

[bakalorz]

Steve,
Thanks for the reply. I wanted to clarify a point or two. The readings you get with an analog voltage meter are not terribly accurate so I'm not overly concerned with the values other than the 13+ charging voltage only appearing at 2000/2500 revs. In my experience it should rise to this level at any revs over 2500 so when it doesn't achieve it at 3000+ but does when it drops to 2500 again I begin to wonder.These findings are abnormal and I was looking for confirmation which you provided.

Your voltages seem somewhat low, but the general behavior is not way out of line.

The following is slightly simplified, but basically correct:

The GS's have shunt regulators.
What that means is that they control the voltage by momentarily shunting the stator (shorting the stator to ground)
Because the Stator puts out AC, the easiest way to do this is by taking the stator leads and connecting them to ground with something called an SCR. An SCR is turned on by a brief control pulse from the regulator, and then stays on until the current on it goes to Zero. Because the stator puts out AC, the waveform is going back and forth constantly, and goes to Zero from positive once every cycle.

What ends up happening, is that at idle, the stator voltage is low, and the regulator part of the R/R is never triggered on. Because the stator voltage is low, the average charging voltage is low too.

As the RPMs begin to rise, the stator voltage rises, and the battery charges better with increasing RPMs. The stator voltage is rising, but still not high enough to trigger the regulator to turn on.

As the RPMs rise to 2000 or so, the stator voltage gets to just barely below the trigger point which will cause the regulator to start shunting the stator. This is the highest charging voltage you will get.

Somewhere just above 2000 RPMs, the stator voltage rises high enough to
make the Regulator start triggering the SCRs. At RPMs which just barely cause the Regulator to trigger, it will allow most of the cycle through to charge the battery before it triggers. So the charging voltage is still fairly high, but starting to drop

As the RPMs get higher, the Stator voltage rises more quickly, so the regulator triggers the SCRs earlier in each stator's positive half cycle.
So although the stator would charge even higher if it could, less of each cycle is allowed to go through. So the average charging voltage actually drops as the RPMs go higher.

As the RPMs go higher and higher, less and less of the stators current is allowed to go through, and the battery is charged less and less.

This isn't optimum, but in general it works well enough ...
Usually the peak is higher than what you were measuring, and the charging voltage is acceptably high for most RPMs.
The exact behavior will vary based on many factors (load, temp, regulator charachteristics, stator charachteristics)
But the general behavior of the voltage dropping off above 2500 rpm or so is more or less normal.

It's hard to say if your system is OK or not.

[Steve]

My wife's 850 shows the highest voltage with the tach right around 2000 rpm, then drops slightly as the engine turns faster. Example: 14.2 volts at 2000, 14.0 at 3000, settles in about 13.9 at 4000. I consider this somewhat normal, even acceptable, as anything over 12.6 volts is actually charging the battery.

However, I have noticed some other stuff happening which is leading me to believe that it's time for a new stator on her bike, so will be doing that soon.

As BonanzaDave suggested, it might just be dirty connections, but spending some time with your multimeter (analog or digital) and the Stator Papers will quickly identify the culprit. By the way, there are times when an analog meter is better than digital, like watching fluctuations while the turn signals are operating. Depending on response time of the meter, neither one will give you completely accurate numbers on the extremes, but the pattern is easier to follow by watching a swinging needle.

Happy hunting. 8-[


.

[spyug]

Thanks Martin and Steve,

More good information to digest.

After lunch but before reading your posts I fired her up (and oddly didn't need any choke). I let her run on idle for 10 minutes or so and watched the needle in the voltmeter once again. Readings were different again but in line with what you have said.

I now notice maximum charge of a hair over 13v at between 1500 and 2000rpm. Revving to over 3000 brings the charge down to about 12.1 to 12.4v. So while there is a positive charge being produced it is still likely under optimum.

As planned, I'll be cleaning things up on the weekend and will also string the ground line to battery as suggested and test the individual components if time and chores permit..

I have a feeling that things are essentially ok but cleaning of contacts is definitely in order for a bit better charging performance.

Thanks again fellas.
Cheers,
spyug

[spyug]

I think its sorted !!!!

Since I got caught up at the office I decided to play hooky this afternoon and snuck out to the man room to tackle this charging challenge.

After spending 10 minutes trying to find the R/R ( what a silly place to put it:shock I pulled off the connector and cleaned off the spades. Took a length of 12 guage, jammed it in to the ground socket on the connector and wound the other end around the negative battery post. Reconnect and fire up. Immediately the volt meter needle slides to 14V and the multimeter shows 14.5 across the battery poles. As the bike warms up and the revs drop the charging goes up into the 15v+. I think we have a winner!

Shut everything off, disconnect battery and do a workman like job of soldering the lead to the negative wire at the connector and add a crimped and soldered ring connector to the battery end. Tuck everything back in and reconnect negative battery terminal...fire up the LEM and instant 14+v.

At a steady 1100 rpm idle I notice the charging across the battery poles goes up into the 15v range which worries me a bit until I realise it will go down under load.

So all is good with the world once a gain.

As this is a pretty quick fix I've got to recommend this should be SOP for GS owners whether or not they are currentley experiencing any charging issues.

Thanks to Martin, Steve, Dave for the input and suggestions.

Cheers all,
Spyug.

[Steve]

One of the resident electrical gurus on the board is Martin Bakalorz.
Concerning what you just found on your bike, his signature says it all:

The FIRST two steps in troubleshooting ALL charging problems are:
Run a direct wire from the regulator ground to the battery negative.
Replace the stator bullet connectors with spade type connectors.

Nice to hear about a quick, easy solution to your problem. \\/


.