Headlight On for Safety?

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Dec 26, 2007
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My limited experience (one week) in driving my '68 Commando indicates that I will run down the battery if I drive with the headlight on. I ran it down to 6V on the weekend & could not get it to start after a short stop for gas.

I charged the battery to normal charge 12+ volts & started the bike easily. Went for drive with a digital meter & the readout fluctuated erratically between 12V & 18V. The Ammeter runs steadily at roughly 1/4" into the positive.

Is all of this normal? If so, is there a fix so I can use the headlight without draining the battery?
It's the AMP's left after everything is running at speed that will get you. The volts are a little hard to read on a meter as you go along. If you have a habit of going along at 2500-2700 RPM most of the time you will have issues most of the time. JMO. If you found an AMP meter and interrupted a battery connection with it you would see that it's just straight math. At your favorite RPM you need at least 1/2 of an amp left over with all your lights running to keep the battery alive. With AGM battery's you need high volts and low AMP's to keep the battery happy. Lead acid types seem to be more tolerant of one AMP and anything over 12 volts where as AGM's seem to like 15-16 volts and a 1/2 of an AMP. Fitting an LED tail light will help leave some power for the system and all my bikes have them and a single phase stator and a fresh rotor for their strong magnets. That works for me you have to check your bike. I run at at least 3500 RPM by selecting the right gear on long rides with lights on. No simple answer or product to fix this, read an amp gage used as a tool for a bit to find your situation.
Here, it's the law...all of the time, lights on. Actually a good idea as the dummies behind the wheel see you sooner. All my charging foes went south with the installation of the LED tail light, even with the old weak alternator. You problems will be fixed too...listen to the gurus... :wink:
Sorry, but I'm not sure which one to use from the second link. Is the correct bulb for a positive ground Norton the non-polarized one?
From an engineer's perspective, I can't see why positive or negative ground should be an issue as long as the LED is wired in the proper polarity. Am I missing something here?

From a visibility viewpoint and as a car and bus driver, I find the systems that continually switch from low beam to high beam at aboiut 2-3 Hz give drivers of four or more wheeled vehicles better notice that you're out there.

From my experience with the "Prince of Darkness" electrics, it's very probble that his generator system can't handle the headlight being on all the time. I'm sure that some genius on this forum has managed to design an installation that uses a modern generator from Japan or one of the Italian brands, as a replacement for a 1950's designed system that came off the Dominator 77. On reflection, maybe Magneto Marelli isn't that much better than Uncle Joe!

If N-V thought an existing system would work on the Commando, they didn't change it. Saved on development funds!
Lights On

I've fitted a 3-phase alternator to my 920 Commando together with Boyer Power Box. I've also replaced the ammeter with voltmeter. Prior to fitting the 3-phase I could not run with lights as the system wouldn't charge below about 3500. Now the system is fine and I can run lights-on as long (or short) as I wish.
A 3-phase with electronic regulator/rectifier will definitely solve the problem of low charging rate at low engine speeds. I prefer the Lucas RM23 stator and rotor with a Podtronics regulator/rectifier, but many people have had good results with the Sparx system.

However, if you are trying to keep an original look, a new single phase rotor stator may get you by if you are not using a hi-watt halogen light.

In any case, make sure all your connections are clean and tight and use some dielectric grease in the bullet connectors.
I went to a 3 phase in the 80's when the Commando was my ride to work. Never need to worry about the battery even with a H4 fitted.
I was wondering to those who have gone to a 3 phase, what kind of volt output do you have at idle with lights on? how much at 2500? My new sparx does not seem to put out at low rpm, barely 10.5 although charges like crazy at 3500 and over. i am in the process of trying a different replacement regulator/rectifier. Will a LED tail light conversion make a big difference? any input would be appreciated. thank, jerome
The LED tail lights use one third of the power of a conventional one . That's enough to make the difference.
I had the same issue on my '69 "S" several years ago. It was good for about 200 miles before I had to turn off the headlight to make it home. It turned out to be a weak rotor. I replaced it with a used one from a local shop and haven't had another problem with the charging system since. (Knock on wood!)
Jerome, something's wrong with your setup (quite possibly the regulator). I don't recall the exact specs, but my Sparx 3-phase produces very healthy voltage from idle up (high 13s as I recall). Hits 14.3 or so by 2000 RPMs.
thanks for the input norbsa and brian. brian, i thought i remembered reading that after the new regulator came, your problem was fixed with quite a high output. i will report when i change my out. in the meantime i have not had to supplement a charge in 300 miles. p.s. sorry about manny.
Jerome, hi. Yes, initially I seemed to be getting very high voltages at high RPMs. I have not checked recently, but all seems well - knock on wood.

We are quite happy with Jason Bay, thanks!!
Re: " I find the systems that continually switch from low beam to high beam at aboiut 2-3 Hz give drivers of four or more wheeled vehicles better notice that you're out there."

Yes, all the NHTSC etc. studies show remarkably little attention is paid to a steady lamp, far more to a pulsing lamp.
The data I read indicated that anything slower than 1 Hz didn't get any attention, and faster than 6 Hz was seen as continuous (= no response) at medium to long distance. The recco was 4-5, is 2-3 now considered preferable?

As an aside, a lamp that pulses to the observer need not vary function, but instead direction. A locomotive "Mars lamp" rotates alignment about 10-15°: up, left, down, right, repeat so it's noticed even by those out of its normal attention field of view.
What are the pulsating or rotating headlight options for positive ground stock Commandos? Do either or these cause more or less of a battery drain?
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