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Registered Badass
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102 Posts
Discussion Starter #1
New MF battery, Stator, MOSFET R/R, Iridium Spark Plugs, LED Tail Lights, and a used Ninja Junction Box..

I'm now seeing amazing charging performance. I'm getting 14.5V at idle and it never seems to go over 15V when reving in the driveway.

However, after freeway riding for awhile (about 20 miles) my LED battery meter shows no more charging is taking place. It seems to stay at 12.8 or so volts. Restarting the bike seems to return things to normal.

I checked the battery terminals and they're snug (most of that wiring is new and pretty). Stator wires are also new and don't appear to be shorting out.

What I'm wondering is if the MOSFET R/R or even the battery itself has some kind of over-charging protection that is kicking in. I would suspect the new R/R would have some kind of feature like this but I can't find any documentation on it.

At the end of the day the battery is getting charged fine. But I want to be sure this is normal behavior.
 

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1986 VN750
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3,255 Posts
I would test the stator when it is hot to make sure you get the same readings when it is cold.

I do not run the MOSFET R/R so I do not know of any over-charge protection built into the unit.
 

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Registered Badass
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102 Posts
Discussion Starter #4
The meter is from Kuryakyn. It's been good to me over the years.
http://www.kuryakyn.com/Products/872/LED-Battery-Gauge

The R/R is from http://roadstercycle.com

I have double checked with a DVM but not while the issue was actually happening. But this happened twice, once on the way to a location 25 miles away. And again on the way back. Once I got it home I checked all the wiring and voltages and things seemed normal again.
 

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Sparky!!!
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8,697 Posts
what wire is the volt gauge wired to? this will also affect weather it reads correct or not.

In a stock system, it should be wired to the brown wire. With the Shindegen R/R you should be running a relay hot off the r/r battery wire, grounded out to the r/r ground, and triggered off of the said brown wire. (I assume all MOSFET R/Rs wire the same.. but not sure.)
 

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Registered Badass
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102 Posts
Discussion Starter #6
It's been many years since I wired the gauge. It's connected to a switched power source in the instrument cluster but exactly where I can't recall. It's grounded to the frame. It has never given me inaccurate readings since I've installed it.

As for the digital meter (or an analog I used from time to time), I usually check it right at the battery.
 

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Sparky!!!
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8,697 Posts
if you wired it a long time ago.. you wired it to the brown wire.. brown wire used to tie into the r/r through the junction box... the stock r/r used this wire to sense the load placed on the electrical system but now it doesn't.. like I said with a MOSFET R/R the volt gauge needs to go directly to the battery.
the red wire in the diagram can be the accessory lead in the head light bucket since it ties directly to the battery inside the JB.
 

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Captive New Yorker....
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264 Posts
I sent my stator to Tim Parrett, and had it rewound. Does this mean I still have a "stock" stator? Would that effect the wiring of the voltage gage?

I really need to get a gage installed so I'm never stranded again...
 

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Sparky!!!
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8,697 Posts
I sent my stator to Tim Parrett, and had it rewound. Does this mean I still have a "stock" stator? Would that effect the wiring of the voltage gage?

I really need to get a gage installed so I'm never stranded again...
even if Tim wound your stator for more output, it wires into the charging system with out any additional mods, the only time the volt gauge needs to be wired differently is when you remove the brown wire from the voltage regulator as with a MOSFET R/R upgrade.

a cheap and good Voltage Gauge that many of us are using can be had at tractor supply for under 20 bucks
 

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Premium Member
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5,236 Posts
New MF battery, Stator, MOSFET R/R, Iridium Spark Plugs, LED Tail Lights, and a used Ninja Junction Box..

I'm now seeing amazing charging performance. I'm getting 14.5V at idle and it never seems to go over 15V when reving in the driveway.

However, after freeway riding for awhile (about 20 miles) my LED battery meter shows no more charging is taking place. It seems to stay at 12.8 or so volts. Restarting the bike seems to return things to normal.

I checked the battery terminals and they're snug (most of that wiring is new and pretty). Stator wires are also new and don't appear to be shorting out.

What I'm wondering is if the MOSFET R/R or even the battery itself has some kind of over-charging protection that is kicking in. I would suspect the new R/R would have some kind of feature like this but I can't find any documentation on it.

At the end of the day the battery is getting charged fine. But I want to be sure this is normal behavior.
could it be your battery is reaching full charge and the system senses it and when you shut it off and crank the bike it starts charging again because the battery was discharged some?Is it doing any thing else odd?Running differently,missing or whatever and since it has been several years since you installed it it could be the gauge itself,

I would do like Slim suggested and check it against another gauge,before I worried about he system much more :smiley_th
 

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Registered Badass
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102 Posts
Discussion Starter #11
Ok, I dug into my wiring and found that the gauge is wired to the Y/R wire. Which comes off the kill switch. So aside from the ignition switch and the main fuse, it is connected straight to the battery.

The gauge showed the same 13'ish volts for my ride to and from work today. It did go higher on occasion but only for shot periods of time.
After having the bike sit for a few hours I checked the battery and it's reading a solid 12.80V.

I'm starting to think the MOSFET turns down the juice when the battery's fully charged.
 

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Premium Member
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369 Posts
I believe this is related to the reports of lower charging voltage at higher engine rpm. The cause for lower voltage indication, I think, is that the charging voltage actually is pulsed DC above the battery 'idle' voltage. When the battery is full, shorter pulses are needed to satisfy the overall current consumption, resulting in lower average voltage. The pulse height (the peak voltage) still remains the same.

The regulator operating principle is quite simple, it just cuts off the output from the current stator phase when the voltage rises above a fixed threshold (about 14.5V), and the output stays off until the next stator phase becomes 'active'. There is no other overcharging protection in the regulator.

When you have a voltage indication lower than you think it should be, you could test this theory by adding load to the system. Connect an extra headlight bulb or battery, and the voltage should actually show a rise.

For the voltage gauges to correctly show the charging state, they should indicate the peak charging voltage. I suspect many of them, if not most, show the average.
 
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