Reducing load on the rectifier..bad?

[kyle]

Howdy all
I recently purchased a trucklite LED headlight which slots into an OEM 7" bucket. I'll be fitting this on the coming weekend.
However I've been doing a little bit of reading regarding the R/R and it's shedding of excess power when load is removed.

Am I likely to be putting more heat dissipation stress on the rectifier by reducing the overall system load?

OEM H4 ~4.8A on low beam
LED 1.4A on low beam.
LED 2.8A on hi beam (uses both hi and low)


Is this going to cause me serious issues?
I'm in the process of fabbing up a relocation of the rectifier (while leaving the breather tank in place)

Cheers
Kyle.

[Slide Panda]

Paging SuzyJ...
I'm betting she would have a good answer for you.

You'll just have to wait as she's on the other side of the planet

[kyle]

Got a furry feeling she's on my side of the planet

[Slide Panda]

You're in Oz too?

[kyle]

Certainly am

[Slide Panda]

Ah well - then she is. Hopefully she'll spot this, I'm sure she'd know. And I'm curious as to the answer. I'm sick of the awful stock lamp on my 2000. Some new lights would be nice.. but not if they are going to melt something else down.

[zooom]

Ah well - then she is. Hopefully she'll spot this, I'm sure she'd know. And I'm curious as to the answer. I'm sick of the awful stock lamp on my 2000. Some new lights would be nice.. but not if they are going to melt something else down.

I hear ya, as I was thinking about an LED headligh for the trackbike when converting it back to street trim and was looking at something like this to adapt -> http://www.jpcycles.com/product/360-628

[Speeddog]

 

[suzyj]

Your reasoning is sound.  The rectifier/regulator shunts excess power to ground, effectively shorting out the stator when the stator voltage gets too high.

By reducing the load, there's more power that needs to be shunted, so the rectifier/regulator will get hotter and reliability will suffer.

There are a range of things you can do, in increasing order of complexity:

• relocate the stock rectifier/regulator so that it gets better airflow.  On most monsters this means buying a filter for the crankcase breather to get rid of the crankcase breather canister, then buying or fabbing a plate to mount the rectifier/regulator on upside down, so that its cooling fins are in airflow.
• Replace the stock rectifier/regulator with a MOSFET one, such as the Shindengen FH012.  The mounting holes for this unit are on 70mm centres rather than 80mm, so some fabrication will still have to be done. MOSFET regulators replace the thyristors that shunt the power in your stock rectifier with MOSFETs, which have (at least in the case of the FH012) less voltage drop when they're switched on.  The result is significantly less power dissipated in the rectifier/regulator.  The power still gets generated by the stator, but with the MOSFET rectifier/regulators the stator gets shorted out better, so the power gets dissipated in the stator windings.
• Replace the stock rectifier/regulator with a series one.  If you've got the power draw low enough (you probably don't, but if you removed all the lights and ran a smaller battery you likely would), then you can swap from a shunt to a series regulator.  Series regulators operate like a garden tap, where they open enough to only let as much current through as is needed to maintain the correct voltage.  They too get hot, but they make your stator run a lot cooler as it's only being asked to supply enough power to run the bike, not all that it's able.
• Swap the stator out for one that provides less power to begin with. You can buy stators with fewer windings or rotors with less magnets, or a combination of both.  They're used in dedicated race bikes that have no lights.  They make everything run cooler plus giving you a gnat's whisker moar powah at the wheel. It'd be interesting to see whether the stators available for racing do enough power to run an led headlight and a small lifepo4 battery...

Of course some combinations are also good.  You can relocate a MOSFET rectifier/regulator, which is what I'm doing on my own bike.

Hope that's cleared things up.

[kyle]

Thanks for all that useful info Suzy!!
Think you'd be wanting a stator with extra turns to increase the winding impedance wouldn't you?
Just thinking realistically here (or talking out my ass.. just off nightshift) Do you think that 2 Amps less is really going to make a difference?


As for relocating, could put it up near the horn without having to ditch the crankcase breather.. Should work ok there you think?

[Slide Panda]

Just more air flow huh? Hmmm the old 900 has the rect at the front of the frame directly in the air steam.  Hmmm

[ducatigirl100]

Well my regulator burn out today . It was literally on fire!  I add to stop by the side of the road to put it off!  I've installed some integrated taillight one month ago ...don't know if it's related ... The only sign was my headlamp really dim since 2 week ago

[tangoman]

i have done this on my 696 for the past two years ride bike every day with just LED day light on about 36000 kms and the stock R R is still ok but the RR on the 696 is at the front with good wind flow