Floating The Ground On Stators For Full Wave Conversion

[ryan_ott]

This has been covered in brief before but I wanted to try to get some exact locations and pictures for anyone thinking of doing this. Why would you want to float the ground - more stable voltage output and to run higher wattage lights. Dc powered lights will be the same output at idle or max rpm. Maybe you have more accessories you want to run. A quick test showed idle charge rate is about the same as stock, just off idle ~2200rpm I was at 13.8 with a 55watt lamp connected, ~3000 rpm was about 14.2 and held that for the entire rev range. This was using the trail tech 7004-RR150.

For starters remove anything connected to the mounting plate (ground). You are trying to make one long stator winding with only a start (1) and end point(3). For the original center tap (2) once removed connect that to one of the leads where there were 2 wires connected (3). I didn’t need any additional wire just a slight unwrap on (3) and I could reach (2). Solder, heat shrink and epoxy into place. I used JB weld clear and it seemed to work well. Connect new ac leads to points (1) and (3) those will run to the yellow leads on the regulator/rectifier. Again make sure they are secure connections, solder, heat shrink and epoxy to keep them in place. From here you can either wire the reg/rec straight to the battery through a fuse (15A is plenty) red to positive, black to negative and cover the unused red/black or wire the red/black to the input of the headlight switch, you were doing this for lighting after all. It’s actually a rather simple task just don’t over think it. If anything is unclear let me know and I’ll try to explain it better.

*based off of a Zuma/Minarelli stator*














*attempt at your own risk, me nor 49ccscoot is not responsible for you damaging your bike, stator or yourself*

[90GTVert]

Since Ryan was kind enough to share the above post, I thought I should add info from my own posts that have been in T2's build thread for 7 months that I've never put in the Tech Library.


My first attempt at floating the ground on a stator was with a HOCA (same as some NCY) racing stator with a small flywheel for the Minarelli/clone 2Ts. It uses 7 small windings for charging/lighting, but some older models had only 3. They have reduced output compared to stock, with the advantage of a quick responding engine from the reduced flywheel mass. I thought that perhaps floating the ground and using a full wave rectifier would make it better for street use.








Here's a diagram of where wires are going  that I made after my first look at it.











This is what I wanted to achieve to float the ground and ready the stator for use with a full wave rectifier.




I checked and got 0.7Ω from yellow/red to ground and 1.7Ω from white to ground, so white should be the farthest away.

What I needed to do was to cut the bare winding before it reaches the ground wire (3). Then cut the yellow/red wire (4) off and run it over to attach to that bare winding (3).


Being my first time attempting this task, I wanted to explore a bit more to see if I was indeed correct on where everything went. This was not totally necessary, and I will show another conversion later without stripping the stator down so much. 

I pried wires out of their little grooves and I could get the stator free a little, but it really didn't matter. Couldn't see anything for the wrap.




I stripped a bunch of fiberglass stuff off till I could see for sure what was up.




There are 2 exciter coils with fine wire windings.



The yellow/red wire is in the middle of the charging/lighting coils.






White ends one side and that bare to ground ends the other.








I cut the yellow/red wire off, leaving the ball of solder to be sure the 2 coils stayed joined.



I cut the bare wire from the ground point.




Soldered the yellow/red to the bare wire.




I wanted to seal the stator. The stock material appeared to be a really thin fiberglass cloth wrap with a little resin added in spots, so fiberglass should be one option for sealing. New connections needed to be covered with something as well, especially with one being near the chassis which would be a ground.

I went to Wal-Mart and picked up 2 JB Clear Weld for under $10. Turns out, if you use even 1 of these on the stator, you're gonna have a mess. At least on this little stator. All said and done I don't think I used 1/2 of 1 of these packs. 




I started putting epoxy on the outward facing side of the stator. The extensions are there to hold a wire where it needed to be, because wires must be kept away from the rotating flywheel that will be installed over it on the engine.








Later, I checked out the epoxy that was applied. I went a bit wild I suppose, because it puddled and formed globs in spots from running. Nothing that caused a problem though.






I flipped the stator over and propped the plate up and applied epoxy to most of the other side.




Off and on for 2 days, I finished up coating the stator and got it back together. It doesn't take long each application, just had to wait between them so I didn't flip it over or re-position it and epoxy the stator to the workbench or something. Would be easier if the whole stator was off of the plate, but not a big deal and not worth the risk of stripping off really tight cheap screws to me.



I put a few layers over this area for extra insulation, being paranoid about it being near the plate which would be a ground.














Once it was back together, I was curious about the lump in the stator wiring. I thought perhaps it was a connector that I could get rid of. After stabbing myself in the tip of the thumb with a utility knife, I removed the heat shrink and this is what I found. I couldn't tell you what it does with any certainty, but it's on the exciter coil wire and attaches to the ground going to those coils as well. Nothing of concern for the process of floating the ground.










Luckily I ordered some big heat shrink when I bought wiring supplies some time ago, so I recovered it.





I used a Trail Tech 7004-RR15 full wave regulator/rectifier for my conversion. The Trail Tech rect/reg is larger than the stock unit and the wires stick out in a different way, so it wouldn't just fit where I had the stock one and had to be mounted in a different area. This was of little concern to me, because I built an entire wiring harness for the scooter from scratch as part of a larger project and to accommodate the changes needed for the new regulator and making my headlights work on DC battery power instead of AC from the stator as it used to be.







Since I've mentioned wiring changes, let me give you a little more info on that. Generally, one of the major selling points of a full wave conversion on small scooters is the ability to switch the headlight(s) over to DC battery power. The majority of small scooters use AC power direct from the stator to power the headlight(s). It is regulated to keep voltage at a safe level to prevent blowing bulbs, but otherwise goes straight to the headlight circuit. This usually means the headlight gets very dim at idle. As long as the headlight doesn't demand too much power, it will get to full intensity once the engine revs enough for AC output to increase. I've used around 100 watts of headlights on the stock AC system before without any complaints at cruise RPM with a stock stator. Smaller stators, like the one that I am modifying here, may struggle to illuminate much more than 50W to full brightness from past experience. Swapping to DC from the battery for headlight power allows the headlight(s) to be at full brightness all of the time. I can't say that it ever really bothered me for my incandescent lights to dim at idle, but LED lights will usually flicker at idle or low RPM. The only possible perk of this is being noticed, because it did seem to draw the attention and stares of others at times. They continue to flicker at even high RPM, but it is generally at a frequency too high for the human eye to even notice it. Constant DC power from the battery keeps LED lights steady and bright at idle.

For this reason, power to the headlight needs to be switched over to battery power, preferably fused and switched for circuit protection and to eliminate the possibility of leaving the lights on and draining the battery. You can just run a wire with a fuse from the battery to the headlight switch in most cases for the simplest form of a conversion, or use an ignition switched battery power source or use a relay to trigger battery power to the headlight circuit when the key is turned on.

The Trail Tech 7004-RR150 regulator/rectifier makes headlight circuit power very simple. It includes an output for lighting that only switches on when it senses that the engine is running. Just connect that wire to the headlight switch's positive power input, with a fuse inline to protect the circuit. Make sure the fuse is large enough to support the lighting that it needs to, but small enough to fail before your wiring does. I tend to use wires rated for much more current than any accessory needs, and then use a fuse just above what the accessory needs so the fuse would fail way before the wiring was in any danger ideally. It only takes a few minutes to add an inline fuse, so don't lose your entire scoot to a fire if something bad happens because you didn't feel like adding a fuse holder and fuse.

Changing wiring to the regulator from the stator is usually quite simple and will vary from scoot to scoot. Here's a wiring diagram that I drew up to give me something to build from when I did my project.

Click for full size.



Building a whole new harness is way overkill and a lot of effort, as well as potentially a considerable amount of money. I spent over $200 building a harness because I wanted to use quality wiring and sealed connectors everywhere. At very least, use good quality wire (even if just for a simple move). If you decide to go big like me, here's the source I used for GXL wiring in various colors and for wires with stripes to allow color coding more circuits than solid colors only would allow : LINK. I used weather pack connectors on most of my connections. They're very high quality and support a large range of wire sizes, but they are very large and harder to hide. If I did it all over again, I would consider metri-pack connection that are smaller in size and capable of supporting most connections for the scooter.








Here are my regulator and stator with weather pack connectors added.







Once my harness was complete, I tried to fire up the scooter. My headlight circuit activated, so there was charging power. That's the good news. The bad news is that I had no spark. I tested and swapped and the end conclusion was that there was an issue with the stator. This was a brand new stator, never used before. I didn't mess with the exciter or pickup, the circuit related to creating and triggering spark. In the end the conclusion was that the stator probably never worked from the start. This leads us to an important lesson. Always try the stator that you're going to use before you do a conversion. Make sure it creates a spark and allows the engine to run (preferably tested under load aka real world or a dyno) and that it produces charging power. Otherwise, you may go through the effort of floating the ground for nothing and no one is going to take your stator back for a return/exchange after it has been modified.

[90GTVert]

After the failure with the aftermarket stator, I decided to move on to a stock stator. I had a couple around, and didn't want to spend another couple hundred dollars on a new performance stator. I noticed that one stock replacement stator was wound more than the other on all coils, which may mean that it has more output potential. Check 'em out.














I chose to mod this one.




I could tell what I was gonna do, but decided to take the stator off of the plate anyway. That was a bad idea and unnecessary to complete the job. Stripped a screw. Ended up drilling it out. Replaced both large screws (M5x1.0).








I cut one end off of ground.




I cut the center wire.




Plenty of wire to move it.




Soldered the yellow/red onto the coil.




Epoxied over it and the ground spot and the place where I cut the wire off with 2 coats.




Switched connectors so it matched my weather pack setup.






Before attempting anything, I checked for voltage on all wires when cranking and it looked good. Checked for spark and it looked strong. Nice.

Hooked it up and cranked it over and it fired right up!




I checked it out and even with the headlight and tail light on (pretty much max load this thing will see aside from adding the minor draw of LED signals or maybe something like a GPS) it gets over 14V charging with just a little rev over idle with a battery that was at 12.9V on it's own.


This task is pretty intimidating at first, but after you've floated a stator the second time is a breeze. There's no reason that anyone accustomed to wiring and soldering can't do this job as long as they have a basic understanding of circuits. Take your time planning it out and executing the tasks and ask for help if you aren't sure about something.

I would also advise floating the ground on a spare stator. Not that it takes very long to do, but this way you can have one ready to swap on in case you ever need it in a pinch and don't have the time to float the ground plus 24 hours to wait for epoxy to cure.


Overall, I have been very pleased with the full wave charging system and DC headlight circuit when using the stock converted stator and Trial Tech regulator/rectifier. No more flickering LED headlight or tail light. No issues with charging. As an added bonus, the Trail Tech regulator allows the headlight to stay on for a short time after the ignition is off, which makes it not only nice for safety but makes the scoot look more high end and modern. No complaints whatsoever with this setup so far.

[90GTVert]

The small racing stator on the other hand, I do have a problem with. I later converted an old version of the NCY/HOCA racing stator that only had 3 windings for charging and lighting. I wanted to see how much it changed the engine with the light flywheel and if the small unit could handle my 42W LED headlight and LED tail light while keeping the battery charged. I had used this stator in the past, and new that it worked at one point. 

To make a long story short, I don't suggest using this style of stator in a full wave system. The output just isn't great enough for even my LED lighting while trying to keep the battery charged. It's worth noting that my scooter is kickstart only, so it didn't even have to contend with any draw on the battery from electric starting. My suggestion would be to leave it AC if you use this kind of stator. It is better to let the headlight dim and flicker than to draw the better down in this case, because otherwise your ride time becomes limited when the lights are used and the lights should be used for safety even in the daytime. The only exception would be a limited use (short operation time) scooter. Even then, I think AC would be the better choice though.

With that said, here's a info from when I converted the second racing stator and it was successful... somewhat. At least successful in that it worked, not so much that it worked as I wanted it to.





I wasn't too sure if it would even work anymore, so I swapped connectors to weather pack and hooked it up to the CDI and ground only. No connection to the reg/rec because it doesn't have a floated ground.



It fired up and I got a little AC power from the charging and lighting wires checking with them disconnected. Not much. 2.6V or so from the yellow/red wire and about 3.8V from the white wire while idling. Way less than what I'd look for from a stock stator, but doing something at least. RPM was showing double or funky amounts.

Here are some pics of how it's setup from NCY. Everything is covered in a hard brittle epoxy.












I chipped away at the epoxy where the ground wire meets up with a ring terminal to ground the chassis and one end of the stator coils.




I cut the wire from the winding free from the ground. Then I decided to get rid of the ground in that area all together. I removed the black ground wire and terminal after cutting the screw so I could use a flat screwdriver because it was junk. Then I reinstalled the screw to hold the stator to the plate.








I moved the ground wire over to another ground connecting the chassis and the pickup coil and soldered it on there.




Then I cut the yellow/red wire off of where it was center tapped.




I ran that over to the end that I just cut the ground off of and soldered it to that.






I coated the exposed bits with 2 coats of JB Clear Weld and let that setup for 24 hours or so before I checked it out.

I went out and installed the modified NCY stator and flywheel. I left the charging wires unhooked at first. Thought it made sense to see if it even ran before replacing those connections to match my harness. It fired on the first kick.



I checked the wires from the stator and got 1.7VAC from one and 1.4VAC from the other, but it was idling lower than when I checked last.



I shut it down and installed the appropriate connector for the charging wires. Then I checked battery voltage. It was at 12.50 at rest.



I hooked up the charging wires and fired it back up. The battery voltage stayed the same. Revved it a little, still the same.



I noticed that my headlight did work though, and it won't work if there's no charging input at all because it uses that to sense engine RPM and let power through from the battery to the lights. To be clear though, all voltages that were taken at the battery mentioned in this post were done with the headlight off. I revved it more (not sure where because it still displays screwy RPM, but kinda high) and voltage did pick up. The problem is, it only got up to 12.55-12.7V. I checked the wires unhooked and they got over 3V revved.



So it does something, prob the same as it did before I converted anything coming from the stator, but not enough to be useful. I'd see 50VAC or more from the wires unhooked on a standard stator and I was getting over 14V charging just above idle with that. This may be enough to power my LED turn signals and tail light if I'm lucky... but no way could I ride far and expect the headlight to keep working.



It clearly likes the light flywheel a lot, enough that I'd say it appears to be essential if I want to really see what this combo can do... but it would only be a toy to take around the block with the charging output.




I wanted to try the NCY stator to see if it has anywhere near enough power for real world use setup for full wave before giving up just based on the numbers I saw revving it on the center stand. Even though it seemed like next to no output when checking voltage revved, I thought maybe I was wrong. It would run a 60W headlight when I tried it long ago out of the box with AC powering the light and then still a charging output. The light would only get bright at high revs though, and I can't be sure that it was even at full intensity.


I put the 4 coil NCY stator back on and checked voltage after the battery had been off of the charger for a few hours. It was at 12.39V. Fired the scoot up and went for a 33 mile ride. I was aiming for 1 hour, but ended up being 55 minutes. Shut it down and checked the battery, which was then at 12.29V. That's roundabout 1 hour with mostly WOT or at least half throttle plus on open roads. Maybe 10 minutes tops in lower speed areas (towns).



That's about as good as it gets for riding keeping the RPM up for the best output from the small stator and still it lost battery power. Now imagine 8-12 hours with at least half of that time in an area that is red light to red light.
I did eventually ride it long distance over about 8-9 hours with the small stator, but I had to leave my headlight off most of the time and even then the battery drained some. Not practical for a real street scooter.