Forum

[Adrian]

Here's one for our electrics experts.



With the 1999 - 2007 four wire alternator stator it is possible to feed both the "regular" AC feed to the regulator/rectifier AND the supply which would power the AC headlamp into the regulator/rectifier, thus ensuring the whole output of the alternator's six windings is available for charging the battery and thus powering ALL the electrics.



However, I am uncertain whether the same would work with the 6 wire Thunderbird alternator, as there is an uneven number of power coils, 3+2 (what would have been the 6th coil is instead the CDI charging coil for the ignition), instead of 3+3 on the four wire version. Could both sides of the alternator still safely be connected to one reg/rectifier unit as with the 4 wire alternator? For those unfamiliar with the Thunderbird alternators, it's one of these, the short red and green wires at the top of the picture are for the ignition only.







Otherwise, would it be viable to run both AC outputs through separate reg/rectifiers and then take both regulated DC feeds into the same battery, assuming common earth points?



I could just run with the separate AC headlight, but I'm looking to use an LED headlamp instead of the usual H4 halogen bulb.



Thanking you in advance.



A.

[stinkwheel]

I suppose one consideration is do you need to do this at all? If you're running an LED lighting unit, how much power is it drawing? I'd suspect you could just leave it all as-is and wire in your lighting to the existing charging system.



I've just wired up my bullet project using LEDs throughout (with an LED H4 headlamp) and I measured the peak draw as 1.6A with the headlamp on full beam and the brake light on. Ignition is self-exciting with its own coil. So even with the tiny 2Ah battery I've fitted, I could run the lights for over an hour on full beam. The largest source of current draw is actually the horn but that's used so intermittantly, it doesn't really matter, that's why there is a battery.



I'm not sure enough of the winding layout to advise on your actual question but I suppose you could also run the headlight on direct D/C through a single phase reg/rec if you were feeling particularly quirky (some of the C90 models have one). My gut feeling is that you'd probably want a balanced input on the coils for the standard reg/rec, depending on how that particular one runs, so if half of one phase has a different resistance, you'd land up with two lower output phases and one higher output one which, if it's bridging, could potentially cause electronic mayhem.



But yeah, you probably don't need to mess. My advice would be to fit your LEDs and wire them up as DC then check the draw. It's probably less than before you started. It would leave a redundant AC phase but if it all works, does this matter?

[stinkwheel]

Oh, the ammeter post is a convenient place to take a DC output to the light switch. Do check the headlight switch layout too though. The AC/DC ones can be somewhat "odd".

[Adrian]

Yes, it's the causing electronic mayhem thing I'm keen to avoid.



Current thinking (sorry chaps!) is to run both AC feeds via separate reg/rectifiers with built-in capacitors, the old AC headlamp feed powering headlamp, speedo and tail lights, the normal supply which would have charged the battery just powering indicators, stop lamp and horn directly. All bulbs replaced by LEDs, including the indicators, so that the whole plot can run battery-less, as the CDI is already battery-independent, no ammeter required and simpler wiring. I'd just have to see if there was still enough power for the horn, otherwise one of those 2AH batteries might be needed after all. Or a bulb horn (don't think the LED horn has been invented yet).



With no pilot bulb a simple on-off switch in the (separate) headlamp shall can control the rest with a dip/horn/indicator switch handlebar instead of the full Minda l/h AC/DC switch. I take your point about these, I have used a couple of on full 12V DC systems and I always forget that I have to disconnect the red and yellow wire.



A.

[stinkwheel]

I know it's not answering your actual question but if the aim is to run battery-less, why go LED headlamp? That's the one part of the lighting system that is already battery-free and in my experience, entirely adequate and capable of running a halogen headlamp bulb.



So the only thing you need to run off the DC phase are the existing flashers, side lights, brake light and horn. LED flashers is a no-brainer, swap out the bulbs for LED ones and fit an electronic relay. A smaller draw than one of those tiny pencils from Argos. Same for side lights.



Now brake lights is trickier. I actively researched this for my project. You CAN use a positive earth LED tail lamp and it will work on AC BUT it will not give you a differentiation between the stop and tail if you then use DC for the stop lamp. So you could run a conventional bulb as AC/DC OR an LED on DC only. OR use a seperate bulb for the stop and tail.



Ok. A little out of the box thinking here. If you fitted an LED stop/tail and used the existing AC feed to activate the tail light via a diode protected relay, that also ought to do it assuming there is sufficient power to keep the relay latched.



So yeah, If I was where you are at. I'd leave the standard halogen headlamp running on AC. Whatever the hype, I still don't believe the LED bulbs are better than a halogen (yet) and your bike already runs one of those perfectly effectively with no reference to a battery. I'd fit LED flashers and relay. Next I'd just try removing the battery and see if it can run the existing brake light as-is and if it can, crack-on, non-problem solved, no need to modify any wiring (I suspect this will prove to be the case, people have been running bullets battery-free on boyer boxes since before there were LED lights).

If it can't run the brake light on the existing DC phase alone I still see three options: 1) Fit a tail light unit with a seperate bulb for the stop and tail. Make the stop one an LED. (this will definately work and retains all the original wiring)



2) Use an LED stop/tail. Use the existing AC feed to the tail light to trigger a diode-protected SPNO relay which will feed DC to the tail light (I haven't tried this but see no reason it shouldn't work).



3) Use a filament stop/tail. Rewire the brake lights so they run off the AC feed too. (My only caveat with this is if the filament bulb will show a sufficient brightness change and you may run into issues when stopped as you'll be doing low revs AND have the brake on).



You can get low draw horn units.



My first motorcycle was a tomos moped. It managed to run filament bulbs in a headlamp, brake light, flashers and a horn off a half-rectified, single phase 6v lighting coil and no battery.

[Bullet Whisperer]

Hi Adrian, I am no electrical 'boffin', but perhaps you could do something along the lines of the old 6 volt systems, where a PRS8 switch or similar could be used to bring the extra power in only when the lights are turned on? Regards, Paul.

[Adrian]

Thank you gents.



@ stinkwheel. I would point out that this is for an as yet totally un-wired project bike, so I can custom-wire it to suit, hopefully keeping it as simple as possible but allowing for the uneven output from the two different parts of the stator that actually produce the power. As mentioned above the CDI bit is totally isolated from the rest of the electrics and couldn't care less about what they're up to...



I know the AC headlight running off the amber and yellow wires is also already battery-independent, but I'm not keen on a halogen H4 bulb dimming at lower revs. The newer LED headlamps, or at least the ones I have in mind draw 2A, also leaving plenty of power for LED speedo and tail lights. They're not AC compatible however (I gather some MIGHT be) so instead of the AC regulator I'll use one of a pair of reg/rectifier/capacitor black boxes, with the other one for horn, stop lamp and indicators as explained. If I can find a Tomos moped horn it will be battery-less heaven!



@ Bullet Whisperer, I can see where you're coming from Paul, but that would probably need a RM19 alternator, and there goes my CDI ignition... With all LED lights coming off a single 12V DC supply and no parking light, the only light switch I will need will be a simple (waterproofed) toggle switch.



A.

[stinkwheel]

I can confirm the (cheap, Chinese, but labelled as non polarity sensitive) LED H4 I tried ran on AC for approximately 0.2 seconds.



But yeah, 1.6A draw (directly measured) from my one with an LED H4 on full beam, with all the dash lights and stop and tail lights on.

[Adrian]

I was of course thinking of something sourced from a reputable UK supplier and run on DC for the H4 replacement.



A.

[stinkwheel]

If you are retaining the casquette, check there is sufficient clearance between the LED bulb heat-sink and the speedo drive cable. Even with an extra-wide electra outer rim, there is one metric gnats cock of clearance on mine.