Overcharging my battery

[Kathos]

So I've been reading into it all day so I could give some helpful numbers to go off of. I'm using a vr-115. A few months old. I had it wired correctly o+y to brown. G to g. Black to ground. My system sits fine at idle but as soon as I rev it, charge jumps to 16.3v on the battery. I checked the voltage into the vr115 via brown wire and it matches at idle and at overcharge.
The green wire puts out 12v at idle and when revved, it drops (as expected) to 8.3v. So whats the problem? Is the regular not dropping enough voltage to the stator?
This is only my 79 sf.

 

[Kathos]

You can't believe everything you find on the internet. The diagram you posted does not tell the complete story. That diagram ( unground the 3 screws) is correct only if you are using a 80 to 83 type of regulator with a 70 to 79 stator/brush alternator. The 70 to 79 years all had one grounded brush, whereas the 80 to 83 years do not.

No stock harness is no problem. The VR-115 orange and yellow wires both connect to the down stream side of the ignition switch. The VR-115 green wire connects to the outer left side brush. The VR-115 black wire connects to a common grounds wire in the harness, or to bare metal on the frame (do not use the battery box).

I have my vr115 wired up with this in mind. I did not change to nylon screws. I am using a mikesxs rectifier only.

 

[TwoManyXS1Bs]

...The green wire puts out 12v at idle and when revved, it drops (as expected) to 8.3v. So whats the problem? Is the regular not dropping enough voltage to the stator?...

Sounds like a bad vr-115, or the supply voltage (brown wire) going to it drops when revved, fooling it into thinking that the bike needs more charge. When the system voltage gets near 15v, that green wire voltage should drop to nearly zero.

 

[retiredgentleman]

When the charging voltage goes high, such as 16+ volts, it quite often means the regulator does not have a good ground connection. With no ground or a poor ground, the regulator defaults to over charging.

You should do a close inspection of where the black wire, from the VR-115, connects to ground. Are you sure its a good solid connection to the common ground wire in the harness, or to bare, non corroded, metal?

You can't use the battery box as a ground because its rubber mounted.

As a test, you could run a temporary wire from the VR-115 black wire directly to the battery negative.

 

[Kathos]

WER, I can't remember if you are using the 70 to 79 type of charging (one brush grounded), or the 80 to 83 type (both brushes isolated from ground).

Regardless, I suspect your problem is the loss of the ground to the regulator. The regulator has to have a voltage reference. If the regulator loses the ground, it sees that as low voltage and supplies full voltage to the brushes. That means the alternator is running at maximum voltage output, that will only vary with the rpm.

When you start your bike, its normal for the brushes to have about 10 to 13 volts across them. Now as you rev the engine to 3000 rpm, the regulator should lower the volatge to the brushes down to about 5.5 to 7 volts.

If you put a volt meter across the brushes, you are likely going to see that their voltage remains high in the 10 to 13 range.

You should find the black wire coming out of the regulator and follow its path to where it grounds to the frame or to the common ground wire in the harness. Look for a broken wire or bad connection along that wire. If you have access to that black wire ground at the regulator itself, try jumpering another ground wire to that point.

If the reg/rec works fine on another bike the problem is on your bike. The reg/rec uses the voltage on the brown wire as reference to compare to the preset value of 14.5 volts. If this reference voltage is more than about .3 volts below battery voltage will make the reg/rec think the battery is low.
The brown wire also supplies battery voltage to the inner brush on the stator.
The outer brush has a green wire to the reg/rec. So battery voltage flows through the rotor to the reg/rec.
When the reg/rec reads a low voltage on the brown wire it turns on the transister and this sends the voltage on the green wire go to ground.
I might check for voltage along the brown wire to the reg/rec and to the brush, from the brushes to the reg/rec. There is a chance the green wire is shorted to ground. Maybe pinched somewhere. In Curly's guide grounding the green wire is how you bypass the reg/rec to test your alternator.
A weak/bad ground on the reg/rec will make the reg/rec it's reading a low voltage.
Check along the black wire from the reg/rec looking for a bad connection, broken wire. On the stock reg/rec the black wire has no connection to the case. So testing this wire can only be done by using the rectifier testing procedures, like on page 180 of the Clymer's book. But having it work on other bikes I doubt this is where the problem lies.
Leo
Leo

I wanna put this here for future reference. I will try a new ground later. Currently its just connected the the black wire back bone of the bike.
Correct me if Im wrong but it seems on the 70-79, the regulator decreases voltage to the green wire to decrease stator output voltage.
While on the 80-83, the regulator decreases voltage on the green wire to increase stator output voltage.

 

[TwoManyXS1Bs]

http://www.xs650.com/forum/showpost.php?p=277348&postcount=7

http://www.xs650.com/forum/showpost.php?p=287614&postcount=13

 

[Kathos]

Makes sense. Basically older model, As volts decrease from the green, the voltage drop across the rotor decreases as well.
On the newer model (80-83 is newer...) as volts decrease from the green (since its used as the ground instead of the power), the voltage drop across the rotor increases.

Do the regulators work opposite of each other?
Im trying to mentally imagine when the screws need replaced with nylon and when they dont. If I had to take a stab at it, I would say that the regulators DO work inversely, and you only need to unground the screws when using a 70-79 stator with a 80-83 regulator, but in that case, I dont know where the stator gets its power from.

 

[TwoManyXS1Bs]

Yeah, you're getting it. On the rotor brushes, the outer ring brush is the regulated line (either receiving power, 70-79, or grounding 80-83).

The inner ring brush will be grounded on 70-79, with metal grounding screws and that u-shaped brush holder.

The inner brush will be powered by system 12v on later 80-83, so you want to ensure that it's isolated from ground, by using proper 80-83 brush holder and housing, or by doing the 3-nylon screw mod to the earlier brush holder and housing.

 

[weekendrider]

Kathos my problem was someone had installed the older brushes in a newer housing/system.
And it does get you excessive voltage. 16-17 volts.

 

[Kathos]

So here's an update. I tried running straight to ground. No bueno.
I did notice a slight change. Maybe someone can shed some light.
@idle with headlight -battery 13.8v regulator red 13.8 green 12.4
@rev with headlight - battery 16.4v regulator red 16.4 green 7
@idle without headlight - battery 16.2v regulator 16.2v green 11
@ rev without headlight - battery 16.2v regulator 16.2v green 4.3
These are rough numbers.
I don't see anything in the p.o. paperwork about replacing the stator. I do know my screws are not nylon

 

[TwoManyXS1Bs]

I've never handled a vr115, so decided to research this. It's configured similar to other regulators of the period. Of those 2 powered wires, orange and yellow, yellow would be switched regulator power, the orange would be voltage sense. The orange could be seeing something unusual.

Edit: Could check for voltage drop where your orange/yellow wires tie in to the switched brown.

The AMC forums stress that the black wire be properly grounded. They want it attached to the alternator case in the car. Perhaps you should triple check your grounds, alternator case to engine, engine to frame/battery, frame to battery, and of course, the regulator black wire.

Here's a good application description: http://theamcpages.com/chargesys.asp

Edit2: The AMC application shows that the orange sense line is tied to the immediate alternator output. That power output then goes through an isolation diode (about a 0.6-0.7 voltage drop) then on to the battery and the rest of the system. Therefore, in proper configuration, the orange wire should be given a voltage that's 0.6-0.7v above the yellow wire...

 

[Kathos]

I ran the vr115 ground directly to the negative terminal. I don't know how to get grounded any better then that.
It seems to me that the stator doesn't care what voltage is coming in. That or it's increasing voltage as green decreases. I'm thinking. If I ground the green wire, the input should be zero. If the voltage drops, the stator is good. If the voltage increases still, then the problem isn't the regulator

 

[TwoManyXS1Bs]

A good test, but you don't need to ground it. Just disconnect the regulator green.

Edit: Fyi, the stator is the surrounding coils, with 3 white wires going to the rectifier, that produces power.
The rotor is the inner rotating coil, with 2 slip rings, that is powered by the regulator. It's also referred to as the energizer.

 

[Kathos]

So this is what I found out. When disconnecting the regulator. The bike does not charge.
When grounding green, the bike does not charge (I did this to make sure it wasn't a new style stator).
When I connected green to power. I overcharged.
Basically what I am thinking is the regulator is the issue

 

[TwoManyXS1Bs]

Ok, well, the only other things I can think of to check would be voltage drops.
With the regulator hooked up, engine idling, check voltage between these points:

Battery positive and the orange/yellow/brown regulator power connection.
Battery negative and rectifier ground line (I actually pierce the wire with a needle).
Battery negative and alternator housing.

Any significant readings could be the cause, else I would think it's the regulator.

 

[Kathos]

New regulator. Problem fixed. Last one was only a few months old. Thanks for the assistance and knowledge!

 

[TwoManyXS1Bs]

Yeah, you bet! I've been wanting to research this vr-115 for quite awhile, and this thread gave me the nudge I needed...

 

[gggGary]

Wonder if there is an all in one mosfet based regulator/rectifier that would work with the stock alternator and if it would be enough of an improvement to be worth doing. Looked around at the Shindengen but didn't find enough info to find one that (w)should work for a field excited 3 phase alternator.

It appears the last type on this page would be suitable.

but they don't show detailed specs there.

 

[TwoManyXS1Bs]

Wonder if there is an all in one mosfet based regulator/rectifier that would work with the stock alternator and if it would be enough of an improvement to be worth doing. Looked around at the Shindengen but didn't find enough info to find one that (w)should work for a field excited 3 phase alternator.

It appears the last type on this page would be suitable.

but they don't show detailed specs there.

Those last 3 are suitable for PMA 3-phase alternators. The first 2 of those are shunt (shorting) types, dump excess power as heat.

The last one is an open type, blocks excessive power, but forces the stator windings to experience high voltage, which might bridge the windings' thin enamel insulation.

For a field excited alternator, it's hard to beat the vr115 for price, performance, availability...

 

[Kathos]

I only see four on the page. It looks like the second rectifier/ regulator would work