Modern Vespa

I'm looking to do an all DC conversion on a p125x with the goal of getting my 35w h4 headlamp bright by switching it over to DC instead of having it run on AC. There was a thread on scootercentral about someone doing it on a stella to install an HID headlamp. But they have a blue/black stator, mine however is the old double yellow stator.

to further complicate the situation, i'm running points while the stella and p200 have a CDI, and worse yet, i have a SIP speedo/rev counter (which i love to death) and the rev counter needs AC.

I put together a possible schematic to achieve all DC and possible AC for the rev counter but i'm new at playing with stators, could someone with more know-how take a look an see if this is right?

the regulator i was looking at is here: http://www.trailtech.net/7003-RR150.html

Those Sip rev counters are awesome. Want

I guess you could splice in a wire with any of the hot leads from a stator coil at the rectifier, and route that wire up to the headset just for the SIP rev counter. Seems like a lot of work just for a techometer though.

you cannot tie the two pairs of coils together on a battery US P to get all of your power out on one circut - becuase of the mismatch theres is some cancelation and you end up with no more power than just running off one of the pairs.

Instead of connecting the 2 pairs of coils in series, connect them in parallel, this will add their wattage outputs together. Make sure you get the phasing right though.
The SIP tacho will work fine off of one of the rec. inputs, as you've drawn it.

may seem that way, but if you've ever ridden with one, i don't think you could ever go back. the amount of cohones you have with a speedo, tach, and cht combo seems to double at WOT for hours on end... I do lots of long distance hwy riding at 55-60 on my stocker. I'm gonna have to pull the tank to rewire the stator and new rectifier, running a wire up through the headset is a no-brainer from there. thank you so much for this! the schematic is confusing because it doesn't specify which way the windings go. So either the left yellow goes with black and right yellow goes with purple OR left yellow goes with purple and right yellow goes with black depending on the phasing. Makes sense to me. then shove those pairs into my AC inputs on my recifier/regulator and it should spit out 80+ watts of DC right?

I'm hoping to get this done soon and do some testing before WKRP in a couple months.

without an oscilloscope, how can i make sure both of the pairs of coils are in phase?

honestly, i hate to brake it to you but i doubt you'll end up with any brighter light just going to DC except for at lower speeds.

have you tried the obvious first; i.e. is your flywheel magnetism up to snuff?
if your headlight has a yellowish tinge then this may be the case.

what kind of voltages at what RPM are you seeing on your headlight system?

So i played around for about 20 minutes with the AC and DC system.

Hooking the headlight system straight up to the battery produces an amazing light through the headlight. one that could actually be seen. I have the PX H4 upgrade with a 35w bulb and it's pretty decent. I would be eager to try a 55w bulb if i get this all sorted out.

I started up the scoot and took some reading on the purple wire which the headlight runs off, in the stator it's grounded at one end and AC on the other. Right at the motor i get about 7 volts at 2000rpm, at the headlight i'm getting about 4.5 volts at 2000rpm. I couldn't get an accurate reading from right at the motor at 6000rpm, but up at the headlight i could get about 8.5 volts at 6000rpm.

Obviously I'm losing some voltage along the line somewhere, but 35 years of dirt will probably do that to my wires and contacts. Funny though because when i hook it up straight to the battery i get 12 volts DC no problem up at the headlight

I also did a 'look into the light' very scientific test. on AC full revs it's still quite dim, i'll see spots but not for more than a few seconds. On DC however, I had to stop what I was doing for a minute or so before I could see anything that I was doing.

As for the magnetization, I thought of this before a few months ago and was about to send my flywheel in. But funny enough, throw a 19mm wrench on there and it doesn't have any problem sticking to it or dangling from it. I think the flywheel is fine.

From these tests I do think that trying to convert to all DC is still worth it, the headlight is clearly much brighter throughout my rpm range on DC. And although at idle, i'm not pulling many volts on the AC, while riding the amount of current that could be flowing into the battery would easily make up for it. Plus, if I wanted to go with an HID headlight in the future I would need to do this anyway, or if i wanted to add a 12v socket I could spare the power.

Anyone done an all DC on a single yellow wire stator? Looking at the schematics the stator appears the same but just has a different rectifier/regulator.

so your comparing a healthy battery to your bike's headlight generation system.

also going to a 55watt bulb will most likely kill your battery if you do go all DC, but more on that later. this right here points to a bum flywheel or stator coils. This partly has to do with the fact that the headlight circuit is a current source and not a voltage source and also seems to be operating well below what it should.

fun fact- on the AC current source system that headlight circuit uses, dirty / higher resistance connections will cause the coils to output more power and blow the bulb, not go dimmer. to over simplify; if the properly functioning system is a 12v battery, yours is acting like a battery that is shot and not putting out the proper amount of power. fix the problem, don't re-engineer your electrical system using the same faulty components, especially if you have to ask strangers on the internet how to do it.

once again, these systems work fairly well when they are operating to spec. yours is obviously not. restore it to full functionality and i wager your headlight will be bright enough to satisfy you without trying to re-engineer the already below-spec system to function in another manner. That's pretty irrelevant. your flywheel does not need to levitate a wrench, it needs to work with the stator to generate power. there are also other factors that come into play with the magnets besides strength; i've seen ones remagnetized improperly by either incorrect use of a machine or hooking up a battery to a headlight coil accidentaly that would hold anythign you would throw at them but wouldn't generate power worth a damn. You'd think it is worth it until you end up with a consistently dead battery. if the headlight coils cannot generate enough power to light the bulb as AC, why will they generate enough power to light it once you add in the losses of a regulator/rectifier stack?

the net result is you'll add more load to your battery, and add less charging capacity than that load since the headlight coils are not operating up to snuff.

and if your headlight coils are not operating up to snuff, i bet your charging ones aren't outputting their rated capacity either.

batteries do not generate power; they merely store it. the extra power you want to direct to your headlight has to come from somewhere.

i'd wager if you put an ammeter on your battery side you'd find you do not have much extra charging capacity to spare, especially if you put a headlight load on the battery as well. if you still want to do this, your best bet is to go to a different, later stator. the ones with separate AC and DC systems actually generate less power than the later style combined ones. and the later combined ones are much easier to hook up in the manner you are contemplating.

but there's an even better option that would fix all your problems for around $400; the Vespatronic ignition system.

It runs higher output than stock, will run your headlight at full brightness and charge your battery. minimal modifications to your stock wiring setup. it also has a variable ignition timing, electronic ignition, and a stronger spark so your bike will run much better than it ever will with what you have. it comes with everything; cdi, flywheel, stator, flywheel puller, regulator, flywheel holding tool, connectors, etc.

if you have a points P125 and are having power generating issues it's the first thing i'd recommend because it will fix this problem and other ones you don't even realize you have.

I'm not completely stupid when it comes to basic electronics, I enjoy designing and building tube amps for fun, but i'm also not very smart, so please help me learn here...

If at the point near the motor i'm getting 7v and at the load, the light, i'm getting 4.5v where is the current disappearing to? it must be traveling through some sort of resistance right because not all of that current is getting through? and if you say that resistance increases the load on the coils to output more power, the opposite seems to be happening here.

I understand what you are trying to say about where is the extra power going to come from. Right now I don't have any problems with battery SOC while having my phone plugged into my 12v socket on my DC side and my SIP Speedo also powers up on DC. But if i'm getting 7 volts AC at idle at the stator, i'm definately getting much more at cruising speed of 6000rpms which if I put in new wiring to decrease resistance going into a rec/reg there might not be a problem. Just basic math says that i've lost 1.5x the current at the load, which means that at 6000rpm i'm producing at least 13v, not a ton but at least that's something that could be put back into the battery.

What sorts of voltage should i be seeing off this purple wire both at the motor and at the load at idle and at 6000rpms?

Again, not to be combative, I'm just trying to learn and understand so I can become more informed about my scoot.

I agree that having a more modern Blue/Black stator would make this a whole hell of a lot easier, but then it wouldn't be worth the discussion either and I wouldn't take the time to learn something. For me, it's not just about having the the scoot 'done' is about the learning and exploring along with it, like a friend.

those vespatronic systems are super kick ass, i've been drooling over them for a while. Maybe someday when i fall into a swimming pool full of money i'll get it along with a pinasco cylinder, a PM evolution pipe, and some tubeless rims.

I also just had a thought, the purple wire, AC, is only half wave, if I floated the ground it would be full wave thus boosting the power output to be rectified.

where are you taking your ground from in these measurements?

A key thing to get here is that this is *not* a voltage source system like you are used to seeing from a battery. this is a current source system. the important difference here is that in a voltage source based system, as you increase resistance, the power flowing thru the circuit decreases. in a current source based system, as the resistance increases, the power flowing thru the system increases, within the limits of the system to supply power.

to explain why is a whole 'nother 3 or 4 page thread i could dig up for you but suffice to say it's goofy and counter intuitive, and just the way the unregulated systems work. these are inconsequential loads compared to the 35w headlight. peak output of a cell phone charger is typically 500ma @ 5v, which is 2.5w. (at 5v, mind you). and that's the most it puts out, with a completely flat battery. as your battery charges, the rate of charge slows down, so if you have half full on your cell battery you could be drawing half (or less!) of the maximum rated output.

I also really doubt the SIP speedo is drawing more than a few hundred milliamps.

but put an ammeter across the circuit and you'll get a much better idea of what these loads are. you'll find them to be a pittance compared to a headlight. decreasing resistance may decrease the amount of power put out b the coil. yes, i know that sounds crazy, but yes, it is true.

as i asked before i'd need to see your methodology on where you're getting your ground from, but yours is not sound theory. voltage is (sort of) irrelevant here if you don't know current. your voltage will fluctuate depending on what the resistance of the circuit is, in accordance with watt's law.

to relate it to speed- it's like knowing the miles you traveled or the time it took you, but not both. each is meaningless without the other if you want to know the rate of speed. it depends immensely on the load.
the current is *somewhat* constant, but the voltage changes to match it, in the same way that the current output of a battery changes depending on how it is loaded. no problem.
i'd just hate to see you completely rewire your bike and end up with a gutted harness and a nonfunctioning electrical system when the design isn't your problem; it's the faulty components. it'd only make it easier if you insist on rewiring your bike to all DC- witch in my opinion is the worst way you could go about fixing this fault. it's a bargain compared to what you're getting. it's not much more than what a complete stock ignition setup would cost you.

but again, with this DC idea you have i think you have a solution and you are trying to force your problem to fit it. borrow a known good flywheel and see if that makes a difference; if you can get a different stock stator try that as well.

diagnose and troubleshoot the stock setup as it is obviously not functioning as it should. My advice would be to spring for the varitronic as you may have more than $400 into this by the time you are done when you figure in parts and putting a price on your time and frustration. if you want one let me know; i an get you a good price on one. no. if it went to a diode to convert to DC, it would be half wave. but as it is AC without any diode rectification, the full wave is being used to light the bulb.



full disclosure here- i'm a bit tired and am heading to bed so some of this might not be as clear as i intended it to be. i may re-read and edit in the morning.

You could disconnect the purple wires at the engine junction box, connect your 35W headlamp directly to the purple and ground from the stator, and then do the stare test to see if it's any brighter. That would let you know of possible wiring/connection problems outside of the stator.

at the motor, purple and black off the stator, at the headlight green/brown pins and black pin, also just to double check used frame grounding at the headlight as well.

thanks blackbart for the input. I'll have to play around with this.

Rob, thanks for bearing with me through this... you obviously are a wealth of knowledge about AC systems and in my electronic experience I have a big fat NONE other than winding transformers, aka getting away from AC asap.

I understand that this is a current based system and not a voltage based one, but that the voltage readout is a reflection of the current. But it still doesn't explain why the current would drop somewhere along the line from the stator to the load. In my DC wired brain the explanation is there is a resistance along the line, but if that's not the case, what could be a possible explanation? So as I rev the engine and I see voltage increase on the multimeter at the headlight, i'm actually not getting more voltage but more current?? at what voltage? always at 12v since i assume both coils are 6v in series? But isn't the voltage still relevant because if I wanted to charge a 12v battery the voltage would have to be more than 12v, no matter what the amperage.

I hear everything you're saying, and some of it i'm digesting slowly. As you said before about talking to strangers on the forum, it all comes with a healthy dose of skepticism. Part of me still doesn't think there is anything wrong with the current system as you seem to think. The system functions as it should, there's no ac regulator as it's an old double yellow wire. the single yellow wire stators appear to go through an ac regulator (5 pin rec/reg) before heading out to the headlight. If i had an ac regulator like this one: http://trailtech.net/regulator.html my problem with the dim headlight would probably be solved, but the idea of running all DC wouldn't. but it also seems there are many with a double yellow stator that complain about dim headlights.

For me, since i'm DC brain wired, one of the ways I see how to measure amperage from the stator is to run both pairs of coils through the trailtech rec/reg and see what spits out on the other end. If the current coming from the TT is greater than the draw from the battery, there's never going to be a problem.

did a couple things over lunch hour...

Hooked multmeter up to purple and black off the stator with purple wire (headlight) disconnected, get 24v AC at 2000rpm idle, up to 45-50v when i rev it.

When I connect the purple wire (headlight) the voltage drops to 6-7v range at idle and could see up to 10v when i rev it.

both of these readings were done right in the motor junction box.

If there's more current under load in AC how can I check this when I see voltage drops?

As for blackbart's idea, i tried it out. The light was slightly brighter but not much when i ran new wires straight to the headlight from both the black and purple wires off the stator at the motor junction box

It would make sense, if you're developing much less current than the system is designed to. as you try and load the stator beyond its capacity, it's power output starts to drop. it's like how voltage drops when you overtax the capacity of a battery.

testing voltage on this won't tell you much about the health of the system (except for indirectly) because the system puts out a (fairly) set amount of current and the voltage is then determined by the resistance of the load by ohms/watts laws.

let me put it this way- the stock system powers a 12v 35w bulb at full power at around 6-7000 rpm. This is around 2.91 amps. this output should be fairly consistent across any voltage the system lands at.

a voltage source system like a battery is the dual of this setup; the voltage stays (mostly) set from a 12V batttery, but the current changes dependent on load.

in a similar, but inverse, relationship the stator puts out a set amperage. the voltage then changes dependant on load. You're still thinking Voltage source. those coils are NOT '6v'. they are a certain amperage (probably around 1.4-1.5 amps. (at their rated RPM)

your system outputs current, and the voltage is a function of the resistance of the system. if you were to put a different wattage bulb tha t is a different reisistance on there, say 20w or 40w, the voltage would vary to seek whatever voltage that the resistance of the bulbs dictates it go to.

(it's a bit more complicated and hard OT do the math here because bulbs are non-ohmic i.e. they are nonlinear in how the resistance increases as the bulb heats up.)

think of it in the hydrological analogy:

a voltage source (battery) is like a pump that puts out a set pressure (voltage) , regardless of the restriction to flow (resistance). the volume of water in gallons per minute (amps) would go down as the resistance increases, as long as the pressure (voltage) is maintained

a current source (your headlight coils) is like a pump that puts out a certain flow rate (amperage), regardless of the resistance (resistance). to maintain that flow rate, the pressure (voltage), will of course increase as the resistance increases if the flow rate (amperage) stays the same. if the system was functioning as it should, you'd have decent lighting. I tell you, measure the amperage and this will probably become apparent that your system cannot power the bulb to it's full potential. that regulator would do nothing for your headlight circuit and current problems; all it does is provide a limiting overvolage protection.

you'll also notice that people complaining of dim headlights are typically using 30-40 year old tired components on their stator / flywheel. coincidence?

my 1998 Ape 50 uses the same style stator as an American market P; it's not a fundamentally flawed system. the easiest way, DC or AC to measure the amperage is to use a meter.
what you are proposing is just randomly hooking things up to see if they work. Figure out the problem, don't just stab in the dark.

you're still focused on your solution so hard and wanting your problem to fit it, rather than focusing on the problem and looking for the solution.

not to be too punny, but the light bulb just went on in my head and I get it.

I didn't have AC current on my multimeter, so i went out and got a nice new one. Here's the interesting discovery i made

Across the yellow wires which feed to my rec/reg i get 3 amps AC at idle and about 3.5 at 6000rpm.

Across purple and black i'm only seeing 1.5 amps AC at idle and about 2 at 6000rpms.

So if each coil is about 1.5 amps I've got either one bad coil and one good coil, or two bad coils because i should be seeing about 3 amps on the purple/black side too.

Thanks RobHodge for pounding this into my brain. Why something so simple i couldn't comprehend???... idiot me. like I said before, it's all about learning and exploring.

looks like i'll still be taking the flywheel and stator off to fix this problem first.

no problem. now that you have measured the amperage, we can do the math and it becomes apparent that if your system were to be at 12V, you'd only be able to light a 18-24 watt bulb to full brightness.

to light the 35w headlight you should be seeing about 2.91 amps.

in addition, you'd only have about 54w peak worth of 12v power if you had gone ahead and tried to go DC; at 35w for the headlight, and 21w for the tail (if stock), you'd have a dead battery in no time.

glad i could help; I jus task that if you need any parts in the future you give my shop a shot.

I do still plan on going all DC, but checking into the coils will now be another step.

I can't remember if I have a double filament brake light or two bulbs. I'm pretty sure I have two bulbs, a 5watt running light and a 10watt brake light. but it does add up quickly. In another thread about LED signal lights, I was thinking about going that route in the future, that would hopefully free up more current for other toys while making me more visible on the road.

Guess what I'm doing this weekend... if you guessed finding my flywheel puller, you guessed right.

Just thought i'd give an update with my current situation (another one of those puns)

took the flywheel and stator off tonight. On examining the coils in the black/purple pair i notice that there was a healthy dent to one of the coils. I decided to wind my own. I used 22 gauge wire because that's what I had laying around. Turns out that 22 gauge is the stock wire. but I think I might do it again with 20 or 18 to see if i can get more amps out of it for when i make my DC conversion.

I soldered it all up, put it all back together, and started the scoot.

I'm now getting 2.5 amps AC on the purple wire at idle, and about 3 at 6000rpms. Headlamp is much brighter!

told you.

now, if i were yo u' still wouldn't go DC. see, having an AC headlight means that no matter if your system charges or not you will have a headlight. you can keep your stock headlight and add a high-outut/low-draw auxilary headlight

i'd get one of these and mount it on the fender off your stock battery system if you want to throw a headlight down the road in the distance. i saw them at the motorcycle show last weekend. i think i'm gonna go this direction on my race bike.

http://www.cyclopsadventuresports.com/?page=products&id=82

Got a solution and an easy one, check out the schematic i drew up.

Think RadShack sells 3PDT switches?

i'd look more into it before wiring that up- the coils are slightly different outputs and you may not find them to be strictly additive- sort of like hooking two different charge levels or capacities of batteries in the came circuit. it
's been eons since i've had to deal with that branch of electrical theory in depth and i really would have to brush up before definitively saying anything but i do remember there was some weirdness to be avoided / aware of.

and of course, there's phasing to worry about.

Alright! So with some help from some PMs I got my all DC conversion and it's super kick ass!

For starters, thanks to RobHodge for helping me find problems with my old AC lighting coils (purple wire).

What I ended up doing was rewinding my own coils on the purple/black wires with 18 gauge magnet wire but both in the same direction. Formerly one coil went clockwise and the other anti-clockwise. now they both are clockwise (exactly the same as the yellow pair). This pair of coils now puts out 6amps at about 12v AC.

I wired the purple/black coils exactly the same as the yellow pair.

As for phasing, this was now a simple issue. The first yellow wire (11 o'clock position) and the first wire in the purple/black pair (about 4 o'clock) go together and the second yellow (2 o'clock) and other coil wire (6 o'clock) go together.

I tested with a multimeter and low and behold, about 7.5 amps at 12v AC!

The coils are in parallel just like I wanted and working well!

I put the pairs of wires through my trailtech and put the battery back on.

At idle I see about 5amps at 11.5v DC coming off the rec/reg. at 4000rpms I hit over 12v DC and at 6000rpms it hits nearly 13v DC and 7amps. Headlight is DC now and dang it's bright! Thinking about switching to 55watt bulb but don't want to melt things.

I've done many longer rides and haven't had a single problem and riding at night is now a joy, before it was just simply frustration.

Thanks to everyone for the help.

In the future when I do a totally new custom wiring harness I plan to put in my AC/DC switches.

If I was going to do anything different, I would rewind my coils with 20 gauge wire instead of 18 to get more volts. It might drop it down an amp or two but I could spare amps for slightly more voltage coming through the system.

Nice informative thread. This one is too, which I found helpful in converting my Rally to 12 Volts AC/DC for last years Cannonball: http://tinyurl.com/2eqsakc

cmstuber, I wonder if you could write up a run-through of what you did to achieve your outcome? Maybe in the project section? It sounds like a really worthwhile modification.
Do you have to start with the 2 yellow wire stator to make it work?

wanna see if i understood you correctly, is this what your final wiring looked like? All 4 coils turned CW.

I'll work on a write up. I think any p-series double yellow wire stator or single yellow wire would work. I think the single yellow wire is the same stator just the 11o'clock yellow wire is red.

this_guy, here's the final schematic.

thanks.

One thing, there is a lot of lack of knowledge, I.e ignorance about magnetism of the flywheel. Permanent magnets lose about 1% of their magnetism every decade so it is highly highly unlikely that a flywheel would ever need to be remagnetized. Like PT Barnum said there's a sucker born every minute.

shhhh, Is that a 13-year-old echo I hear?

You heard it too? I thought I was hearing things!


Hec