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Discussion Starter #1
I just wanted to ask real quick before I set off on a full set of tests from the guide. I recently acquired a Vulcan. I haven't ridden more than a block yet. I'm still waiting for decent weather and for parts to arrive. I want to get all the maintenance up to date (oil change, clean air filters, lube the drive line, change the plugs, etc.). After reading about charging problems that come up with these bikes, I thought I'd better do quick test and see if I'm charging before sinking anymore money in this thing.

I connected my meter to the battery terminals. I keep all my bikes on a trickle charger so the the resting voltage at the time was about 13.2. I started the bike. At an idle (~1000 - 1100 RPM) I get 14.4 volts at the battery. As I rev the engine up the voltage drops to about 13.5 at 5K RPM.

This is a$$ backwards to everything I've read. The fan was off during the tests, just didn't run it enough for it to come on since it was less than 20F in the garage at the time.

It's a stock 89, no mods, no extra lights. About 26K miles. I imagine the ignition system is pulling the voltage down as the RPMs qo up. But shouldn't the regulator compensate for that (if it's functional)? It seems the stator is capable of making over 14 volts.

I wouldn't be worried if I only had battery voltage or maybe a little less at an idle and the voltage increased along with the RPMs. But this is really weird.
 

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The voltage regulator isn't dependent on engine RPMs...only the stator is.

So your stator output seems a bit wonky. But good news is it is putting out enough power to charge the battery even at 5k RPMs.
I'd check (and clean) all your stator connections, your ground and the R/R connector.

There's a test somewhere here on checking your stator output. If do that after the above if you're still getting "backward" readings....but again if you're not going under 13.4 volts I'm not sure I'd be too worried.
 

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I'm hoping a good cleaning may help. I'm by no means knowledgeable about electricity, but I would think that poor connections could cause the voltage reading to go down as current goes up. Isn't that why bad connections seem to get hot - resistance?
 

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That's a short test ride to be testing the stator, specially since you started with a topped off battery.

Start by pulling the charger offline and wait at least 2 hrs. With engine off test battery voltage. 12.4-12.7v would be what you should see with a freshly charged battery after being off the charger for an hour. Start and ride (or rev over 2000 rpm for 5 minutes) for 3-5 miles. When you finish the ride or high speed idol with the bike at 1000 rpm you should still be seeing at least 12.3v and at 2500 rpm at least 13.8v ( I would hope to see 14v+) If you don't you've got a problem. If you do see these voltages ride on and enjoy the hell out if the bike.
 

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...all the testing stuff starts at 15-17 in the manual....diagrams, tables, etc...15-17, 15-18, 15-19....
 

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I had readings like this once too, but the system is fine.
In my case it had to do with LED's that were installed and causing cross-bleeding in the lighting system.

If the battery is not rested after a charge, you will see some screwy numbers (which is what Fool was eluding to). it has to do with balancing the cells internally...some balancing of loads...ying...yang...yada yada. :loser1:
 

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..have a vulcan good day!
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I had readings like this once too, but the system is fine.
In my case it had to do with LED's that were installed and causing cross-bleeding in the lighting system.

If the battery is not rested after a charge, you will see some screwy numbers (which is what Fool was eluding to). it has to do with balancing the cells internally...some balancing of loads...ying...yang...yada yada. :loser1:

Wow ! New & Good Experienced info here !

Read & head !


Thank you Kc

:smiley_th
 

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Just a note. This got my attention so I waited till is was above 20 F to check. I know my bike is charging at all revs. Never had even a low battery, and even today it has not ran in 2 weeks, stored in the cold. Prestart was 12.7 V. Fired up with one crank, temp was 36F. The only electrical thing different is turn signals in saddle bags. These are my readings; 1100=14.34 1600=13.8 3000=13.6 3500=13.4 I had a thought, maybe with the R/R in the cold air it may dump voltage more efficiently?
 

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Discussion Starter #11
I still haven't picked up an AGM battery. But I lowered the idle and got around the same results as smltownr did. I guess the drop at higher RPMs just happens. I did pick up a LED volt meter just to be sure that it's charging when I'm on the road.

Sent from Motorcycle.com Free App
 

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I guess the drop at higher RPMs just happens.
Doesn't sound right, seems like the field on the stator may be weakening as rpm increases. I would look at the ac voltage on the stator to see if it's dropping there too. That could show if it's the stator or r/r.

The dc volts on mine increases with rpm. TPE and MOSFET setup.

Still, you don't have to have 14-14.5 v to keep the battery charged. 13-13.5v should be plenty.
 

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OK..here is a thought for you to ponder....

The stock R/R has a feedback wire to monitor voltage. If this wire is not making a good connection, it may cause the R/R to do some screwy things.

Lets just propose the feedback wire somehow has a higher voltage for whatever reason...
The feedback loop would tell the R/R to dump more voltage...causing the battery voltage to drop. This is NORMAL by design. Most healthy batteries mask this drop in voltage because they act like a capacitor and try to maintain a certain voltage.

NOW...consider this:
Batteries are made of individual cells....some cells may have better capacity than others...which means stronger ones will charge faster and weaker ones will discharge faster and charge slower. The "lag time" for them to stabilize would be a balancing issue within the battery (as I mentioned in a previous post). If the R/R is trying to DUMP excess CURRENT(wattage), it will put a slight drain on the battery. This drain would cause the battery voltage to drop temporarily. Once the R/R stops DUMPING current, the battery will "balance" out and normalize once again.

I believe that seeing a drop in voltage at higher RPM is not something to panic over as long as your wiring is solid, the battery maintains a charge, and the Stator is putting out good AC voltage.
 

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I agree with KC... Try disconnecting the plug from the stator to the R/R, and testing the AC voltage between each of the three leads (yellow wires) coming from the stator at idle rpm, 3k, and 5k. That way, there's no load on the stator, and isolates the test to just the stator output. Also make sure you do a continuity check between the three stator leads, and between each lead and the engine ground... Post your results up here so we can see how they measure up...
 

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Tests completed

Rained all day yesterday so I did the R/R and Stator tests today. My chiltons manual had the ohm values for the R/R but nothing else. It seems that with the values I measured being so far from normal I'd have had troubles, but never did. R/R ohms. Normal values in parenthesis G-B=8.2K (.4-2K) G-M=31K (1-5K) G-A=5.4K (.2-.6)

Stator ohms.... 1-2=1ohm 2-3=1ohm 1-3=1ohm 1-gnd=11.7 2-grd=11.68 3-grd=11.67

Stator [email protected] 1-2=26 2-3=23.7 1-3=23.8
Never a problem even riding 400 miles a day and avg 1000-1250 miles a month. Am powering a small radio, helmet speakers, and a GPS. Just does not seem right.
 

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AC volts from the stator?

edit: I'm confused by the ground numbers. Should be no continuity to ground from the stator leads.

edit 2: If VT means ac volts, those readings are low.
 

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Yes ac vts from R/R plug disconnected. Ohms reading @0 rpm. A1-A3 to ground (scraped bolt on engine) around 12 ohms. Running (@1100 rpm) stator test was AC VT.
 

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Yes volt test was a1-a2 a1-a3 a2-a3 I wrote it as 1-2 2-3 1-3 as opposed to the G M B terminals of R/R. it was the yellow wires from stator 1,2,and 3. Ohm test of stator was A1 A2 A3 to ground.
 
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