Regulator voltage sensor

[Constant Mesh]

On many car all-in-one alternators there is a remote voltage sensor input which is used in controlling the alternator's output voltage. This sensor may sample the voltage at the battery, a critical bus location, or some other location.

Looking at the FJR schematics it appears that the R/R has no remote sensing. It attempts to keep the voltage constant at its output terminals. The voltage at a remote location is controlled by voltage drop and the R/R's terminal voltage.

When one attaches accessory loads at the battery terminals the battery charging voltage will be reduced since the voltage drop between the R/R and battery terminals will increase. It's too bad that there aren't accessible terminals near the R/R for accessory connections. Much better to tap into the system there than far away at the battery terminals.

Anyway if the R/R had remote voltage sensing at the battery it would be better for the accessory loads and for battery charging.

It may be likely that the Gen I's see a higher battery charging voltage than the Gen II's.

 

[Checkswrecks]

I can't think of any bikes that get reference voltage from a remote location. Probably one somewhere, but the hot lead before it comes out of the VR to the battery is the typical sense location.

That's one reason that it's so important to keep good electrical connections in the bike, as the output can just keep increasing and making more heat.

 

[3dogs]

The Regulator/Rectifier (R/R) does not operate like at typical computer controlled charging system in a car (the car’s ECU controls the alternator’s field coils and thus charging output).

In a motorcycle (including the FJR) the stator (alternator) is always at full output when the engine is at 4000 rpm+. The R/R charges the battery and supplies power (amperage) to the other electrical systems (ignition, fuel pump, ECU, lights etc). The R/R “dumps” to ground any addition amps that the stator is outputting. That’s why the R/R has heat fins on it to dissipate the heat generated by grounding (dumping) the extra amperage. When electrical accessories are switched on the R/R reduces the wasted amperage going to ground and powers the accessory (extra lights, electric vest/gloves etc). If electrical accessories exceed the charging systems power output the battery supplies the difference until it can’t (goes dead) and you’re stuck by the side of the road.

It doesn’t make any difference where the R/R senses battery voltage because the battery essentially becomes and electrical accessory after the engine is started (the battery’s primary job is to start the engine—not power accessories). Just like any electrical accessory the battery uses some of the charging system’s output because it has to be charged so it can start the engine when required. Even though the voltage drop between R/R and Battery increases as more electrical accessories are switched on, the battery voltage at the R/R is a function of the voltage drop in the entire electrical system.

 

[Constant Mesh]

No, the FJR's regulator is attempting to keep its output voltage constant no matter what the attached load. As the engine rpm increases the AC voltage developed by the stator windings increases. To keep a constant output DC voltage the regulator has to shunt more and more energy to keep the output voltage from rising.

If you add accessory loading less power has to be shunted by the regulator. When the load reaches the level where no energy is shunted the output voltage will begin to drop below the desired regulated value.

But it still might be desirable to use a remote voltage for controlling the regulator. Any accessory load attached at the battery will necessarily lower the battery charging voltage -- the added accessory current will increase the voltage drop between the R/R and the battery. If the regulator control voltage was taken at the battery the regulator would automatically compensate for the accessory voltage drop and full battery charging voltage would be available.

The FJR's charging system is crude but reliable and simple. It's not very efficient compared to a standard auto alternator system but it seems to be reliable.

 

[3dogs]

No, the FJR's regulator is attempting to keep its output voltage constant no matter what the attached load. As the engine rpm increases the AC voltage developed by the stator windings increases. To keep a constant output DC voltage the regulator has to shunt more and more energy to keep the output voltage from rising.
If you add accessory loading less power has to be shunted by the regulator. When the load reaches the level where no energy is shunted the output voltage will begin to drop below the desired regulated value.

But it still might be desirable to use a remote voltage for controlling the regulator. Any accessory load attached at the battery will necessarily lower the battery charging voltage -- the added accessory current will increase the voltage drop between the R/R and the battery. If the regulator control voltage was taken at the battery the regulator would automatically compensate for the accessory voltage drop and full battery charging voltage would be available.

The FJR's charging system is crude but reliable and simple. It's not very efficient compared to a standard auto alternator system but it seems to be reliable.

We're statying the same thing in slightly different terms. However, the R/R is connected directly to the battery so it is taking a voltage reading direcly from the battery. Just because most accessories are connected directly to the battery as well will not efffect the R/R output voltage in any practical manner. The voltage in the entire system drops as a result of electrical loads and the R/R tries to keep voltage at a pre-set level.

 

[Fitz]

The Regulator/Rectifier (R/R) does not operate like at typical computer controlled charging system in a car (the car’s ECU controls the alternator’s field coils and thus charging output).
In a motorcycle (including the FJR) the stator (alternator) is always at full output when the engine is at 4000 rpm+. The R/R charges the battery and supplies power (amperage) to the other electrical systems (ignition, fuel pump, ECU, lights etc). The R/R “dumps” to ground any addition amps that the stator is outputting. That’s why the R/R has heat fins on it to dissipate the heat generated by grounding (dumping) the extra amperage. When electrical accessories are switched on the R/R reduces the wasted amperage going to ground and powers the accessory (extra lights, electric vest/gloves etc). If electrical accessories exceed the charging systems power output the battery supplies the difference until it can’t (goes dead) and you’re stuck by the side of the road.

It doesn’t make any difference where the R/R senses battery voltage because the battery essentially becomes and electrical accessory after the engine is started (the battery’s primary job is to start the engine—not power accessories). Just like any electrical accessory the battery uses some of the charging system’s output because it has to be charged so it can start the engine when required. Even though the voltage drop between R/R and Battery increases as more electrical accessories are switched on, the battery voltage at the R/R is a function of the voltage drop in the entire electrical system.

You might be the person to ask about my problem. My 05 FJR is no longer keeping the battery charged. This has just started this month. We had to jump it off after a ride and the battery was 10.5 volts. I have replaced the battery recently and when not in use keep it on a trickle charger. Thanks for your thoughts. Fitz

 

[Zorlac]

If you have a voltmeter can you measure the voltage at the battery terminals with and without the engine running after making sure the battery terminals are tight, then post up the voltages you've measured.

Toasted alternator stators can be a problem, but you'd need to make more measurements.

It has all been discussed at length on this forum if you're willing to spend the time searching for the info.

 

[Fitz]

If you have a voltmeter can you measure the voltage at the battery terminals with and without the engine running after making sure the battery terminals are tight, then post up the voltages you've measured.Toasted alternator stators can be a problem, but you'd need to make more measurements.

It has all been discussed at length on this forum if you're willing to spend the time searching for the info.

First off, great picture and great quote. So far my search on the site and here at home is pointing me to the regulater. While the bike is running everything operates fine, lights are bright, instruments, etc. Thanks for your input. Fitz

 

[olsonm3915]

I can't think of any bikes that get reference voltage from a remote location. Probably one somewhere, but the hot lead before it comes out of the VR to the battery is the typical sense location.
That's one reason that it's so important to keep good electrical connections in the bike, as the output can just keep increasing and making more heat.

This one is easy- I've owned at least two Hondas[1] that had Kelvin connections on their regulators. Unfortunately they tied the sense line through the ignition switch where it would see a significant voltage drop due to oxidation in connectors over the years. In both cases I re-wired the sense line direct to the (+) battery post. Note- I did check to make sure the drain from the sense line was insignificant before doing this.

[1] 1986 GL1200A and a 1984 VF500F.

 

[Zorlac]

"So far my search on the site and here at home is pointing me to the regulator. While the bike is running everything operates fine"

Actual regulator failures are a bit more rare, "fine" equates to what voltage at your battery terminals?

 

[Warchild]

First off, great picture and great quote. So far my search on the site and here at home is pointing me to the regulater. While the bike is running everything operates fine, lights are bright, instruments, etc. Thanks for your input. Fitz

While anything is possible... I would be mildly surprised if the R/R was the culprit here.

My suspicions would likely go to the stator.... Gen I's stator seem to have a finite lifespan if the bike has significant electrical accessories that are used frequently, and many, many of us LD types have had to play the Stator Game on Gen I's.

Swapping them out isn't all that tough.... cleaning the old gasket material off is about the biggest ***-pain associated with this task....

 

[Donal]

Now I'm confused but that's not too difficult. I was under the impression that the FJR is fitted with a MOSFET type regulator. This does not ground anything. It monitors the output and when the voltage reaches a pre-set level it simply shuts off the output from the stator. Have a look here - https://roadstercycle.com/Universal%20Mosfe...m%20upgrade.htm

There's a diagram at the bottom and as you can see there is no connection to ground to short anything.

Hopefully someone with a bit more knowledge will come along and enlighten me.

Don

 

[mcatrophy]

Now I'm confused but that's not too difficult. I was under the impression that the FJR is fitted with a MOSFET type regulator. This does not ground anything. It monitors the output and when the voltage reaches a pre-set level it simply shuts off the output from the stator. Have a look here - https://roadstercycle.com/Universal%20Mosfe...m%20upgrade.htm
There's a diagram at the bottom and as you can see there is no connection to ground to short anything.

Hopefully someone with a bit more knowledge will come along and enlighten me.

Don

According to the '06 workshop manual, the regulator is "Semi conductor - short circuit", which implies to me it "dumps" unwanted current by shorting the output to ground.

This is in some ways a safer technique than the "open circuit" method shown in the diagram in your link, because in the "open circuit" method you have the problem of breaking the current through the very inductive coils of the generator, which can lead to excessive voltage surges. These can be quenched, but it's more complex than using the current dump method.

And, provided the system is designed for it, shorting an AC generator doesn't lead to excessive current. The AC resistance, or inductive reactance, provides a current limit, with the rather interesting property that (ignoring any circuit resistance) the short circuit current is independent of speed (the driving voltage is proportional to speed as is the inductive reactance).

But that's all conjecture until someone can confirm the regulator design type.

 

[Zorlac]

Don, you could enlighten us with some voltage measurements.

 

[Donal]

Might be worth having a look here - https://www.shindengen.com/content.cfm/regulator_recitifers at the Shindengen website. You will see there are 3 'Types', Shunt, Series & FET. If you click on the Part Number to the left of Type it brings up a little schematic but unfortunately no words of wisdom (or *****'s guide in my case).

I have sent an e-mail to Shindengen asking for an ijits guide but I'm not holding my breath!

Don

 

[Zorlac]

Since you've already determined that you just have to replace your regulator, this one is preferred.

More here.

 

[Donal]

Since you've already determined that you just have to replace your regulator, this one is preferred.More here.

Thanks Zorlac, that is pretty much what I suspected:

"Now on to the alternative R/R replacement

- as aforementioned this is a good preventive upgrade measure with a better component, not necessarily limited to replacement on failure. Either way, process is the same.

Best widely available R/R on the market today is the Shindengen FH012AA used on the late (06+) Yamaha FJR, 07+ Yamaha R1 among others

What makes it better is that is a MOSFET series controlled device rather than the crude SCR shunt type that is on most bikes until recently and also is a 50A rated device.

MUCH better voltage regulation and runs cooler too due to more efficient devices and control circuitry.

The SCR shunt type consumes more energy in the Regulator itself than the bike is using and dumps a ton of current into the heatsink (feel yours & just see how hot those things run!!!! - don't touch it - you'll burn yourself - seriously!) The problem is exacerbated because their efficiency goes even lower when they get HOT so it's a vicious circle. Heat is the number 1 killer of these devices.

Incidentally its a misconception that shunt type work harder with increased load i.e. higher-wattage lights, heated vests etc - actually, the higher the load on the output, the less work the shunt regulator does in dumping that excess energy and will actually run cooler!!

The FET has extremely low resistance in conducting state and this results in a lower dissipated power from the device while conducting load current, as opposed to the shunt SCR which shunts the maximum current across a significant volt drop, resulting in a higher dissipated power - and resulting temperature, much more so than the FET device."

I guess the pre 2006 FJRs were fitted with something else, which was a 'shunt' type regulator. The big problem with the shunt type is that the stator runs fully loaded all the time. At light bike loads the excess is shunted and as the bike load increases there is less current shunted but the poor old stator works hard all the time.

For anyone with a pre 2006 bike this would a good thing to consider.

Don

 

[Constant Mesh]

Question:

What stops the FJR charging system from overcharging the battery? From the info I've seen it's just a constant voltage system providing 14.4 volts or so. As long as it's not overloaded it delivers a fairly constant voltage. The current output increases and peaks at around 5K rpm.

I don't understand why this system doesn't overcharge the battery? If the battery is fully charged and you ride for a few hours it would seem that the battery might be overcharged.

Don't see how the FJR's system is all that different from a manual charger I use in my garage. Even for the 2 amp output you can overcharge a small battery. It will continue to hammer the battery with 14.4 volts even as the current drops to less than 0.5 amps.

 

[ionbeam]

Even for the 2 amp output you can overcharge a small battery. It will continue to hammer the battery with 14.4 volts even as the current drops to less than 0.5 amps.

Not the first time I've seen this kind of fishing. The shunt voltage regulator in the Gen 1-2 dumps excess power to ground when not consumed by charging the battery or supplying sustaining voltage to the normal electrical system of the FJR. The stator is at a maximum loading of 100% all the time. The charging system of the FJR will charge the battery at the available voltage, the current passing into the battery is proportional to the need, it becomes a voltage to chemical (PbSO4) requirement.