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More electrical power – Wye to Delta stator conversion


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More electrical power for the DR650 – Wye to Delta stator conversion

Many of us would like a little more electrical capacity from our DRs. I did some testing recently and determined I could power an additional 70 watts of lights/accessories and still keep the battery voltage high enough to stay charged. It’s good to know where this limit is but I want enough power for more light, heated grips and a heated vest.

Since there isn’t any aftermarket high output stator available for the DR I started doing some research about do-it-yourself rewinding. I figured I would get a used stator to practice on and see if I couldn’t wind a little more power out of it. So I found a used stator, cleaned it up and started to take a real close look at how the thing is wound. Well, after a couple of hours making notes and drawings I realized I wasn’t going to really figure it out without unwinding it. One complication is that the ignition charge coil is wound on after the charging system coils. Most street going motorcycles don’t have an ignition charge coil. They power the ignition system from the battery. This can be a blessing for us DR650 riders. The charge coil will still power the ignition even if the battery is totally dead giving us the option of a push start. Most other street going motorcycles have to have some life in the battery to run at all and will run poorly with a low battery. A DIY rewind was starting to look like more trouble than it was worth.

There’s a great thread on ADV - Stators demystified – that gave me some inspiration for a new project. It turns out that most 3-phase motorcycles are ‘Wye wound’. Apparently if a wye wound stator is reconfigured into a ‘Delta wound’ arrangement the output current can increase by about 40%. Ah Ha! The light bulb blinked on! I could just reconfigure my stator from wye to delta and have more power.

A wye wound stator is just what it sounds like. It’s wound in the shape of a Y:

wye.jpg

A delta wound stator has the coils connected in a triangle:

delta.jpg

On paper it’s pretty simple to reconfigure the wye to a delta. Just cut out the point where all three coils are connected together and reconnect them to the other end of each coil:

wye_to_delta.jpg

The stator connections are arranged like this:

stator_dr650.jpg

The black and white wires are for the ignition charge coil. They come out of the motor and go to the CDI box. A, B and C are the yellow wires that come out of the motor and go to the voltage regulator. I cut the 3 wires from the wye connection terminal, extended them and reconnected them one to each the of the yellow wire connections. It doesn’t matter which one connects where except you must not connect the wye end of a coil to it’s own yellow wire connection.

With the modified stator installed in the bike it was time for testing. I was able to run 2 additional H4 bulbs on high beam (60 watts each) for 120 additional watts and still keep battery voltage over 13 volts. That’s 50 more watts. Yay! That will give me just enough power to run brighter lights and heated gear all at the same time. Any more load causes the system voltage to slowly drop.

Now I just need some riding time to give it some durability testing. One concern is whether the stock voltage regulator will handle the additional power. One thing I learned in my initial research is the regulator works by shunting extra output to ground. The stator is always putting out as much power as it can at any given rpm. Some of that power is drawn off by the battery, lights, etc. Any ‘extra’ is shunted to ground by the voltage regulator and is dissipated as heat through the regulator and the stator coils. So using the extra power actually takes some of the load off of the regulator and stator.

I’m pretty happy with the results. I don’t know how many miles I’ll have to put on it to feel confident something won’t go wrong. I plan to add a volt meter just so I can keep an eye on it.

This modification is not limited to DR650s. Since most 3-phase permanent magnet motorcycle alternators are wye wound this could be done to many other bikes.

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I guess it's a bit simpler to build in a wye. I imagine if Suzuki had done it in a delta we would just be stuck with an underpowered delta wound stator.😏

Good point! I guess if everything was perfect then I wouldn't be able to improve on the design & have a great time doing it!

also I forgot to thank you for this amazing piece of research, it will undoubtedly help a lot of people. 👍

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I'll be watching for your follow-up review Jeff. This really sounds good. I think lots of us would like to have more light to keep us alive. I have lots of light on my BMWs and I have noticed that the DR is much less visible. The cages are always trying to turn in front of it. Thanks for sharing your efforts. Neville.

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I did some follow up on this mod & it's been told to me that although the current has increased, the voltage will drop.

at higher RPM's it will make an excess of voltage anyway but at idle it may be a problem.

has this been your finding Jeff?

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it's been told to me that although the current has increased, the voltage will drop. has this been your finding Jeff?

Yes, that's part of the equation but in spite of the voltage drop it still charges fine at idle. I measured 14.2 volts at 1600 rpm with no additional load.

I did not concern myself in measuring raw AC voltage from the stator. I do know that it's typical to see around 100 volts AC measured direct from the stator at mid-range rpms. So if that drops to 60 or 70 no problem.

I also did the load testing with the motor held around 4000 rpm which is about 60-65 mph in 5th.

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Yes, that's part of the equation but in spite of the voltage drop it still charges fine at idle. I measured 14.2 volts at 1600 rpm with no additional load.

I did not concern myself in measuring raw AC voltage from the stator. I do know that it's typical to see around 100 volts AC measured direct from the stator at mid-range rpms. So if that drops to 60 or 70 no problem.

I also did the load testing with the motor held around 4000 rpm which is about 60-65 mph in 5th.

it sounds all good then. great work!

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Thanks a bunch for doing the research on this Jeff!

50W extra would be great, especially consider the price.👍 Did you happen to take a picture of the reconfigured stator?

And regarding the regulator, is there anything specific about the DR that would prevent you from using the part of a higher-powered street bike?

Regards,

Lukas

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Sorry, no pics at this time. My camera has forgotten how to focus on close up macro shots. When I modify the stator I removed I plan to get some good pics.

As far as I can tell all the '5-wire' regulator/rectifiers work the same way so they should be interchangeable.

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there are plenty of regulator choices.... if it turns out to be an issue... just pick a regulator from a bike with a higher output stator.. done it many times to get customers going... usually the only issue is when the mounting style changes and you have to improvise a way to bolt it down

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what's the down side of doing this? other than possibly frying the regulator?

why aren't they like this in the first place?

They can be made wither way. It takes the same amount (grams) copper either way. They could have made the exact same thing in the Delta configuration by using 73% more turns using finer gauge wire. Luckily they choose Wye and we can change it to delta to trade voltage for more current.

They are made to charge over the full RPM range. The voltage available is proportional to the RPM. Somewhere near idle, the voltage is around 14 volts. At higher RPMs the extra voltage is shorted to ground by the regulator to keep from over charging the battery.

Changing the connection from Wye to Delta reduces the voltage by 73% and increases the available current by 73%. This means it has to get to an RPM 73% higher before it starts to charge, but it also has 73% more current capability. The down side is the battery might go dead if you leave it idling for an extended length of time. It shouldn't be a problem riding it.

The regulator will have to short out the extra current. i don't know if it will take it or not. My guess is that it will.

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  • 2 weeks later...

Hmmm, gotta wonder if a Delta setup is what they're selling here.

"Redesigned and Improved output Stator. This unit has a higher output capacity than the OEM unit, and will not have the problems that you have experienced with your OEM version."

Might be worth a call to see if they'll put an engineer on the phone.

http://www.regulatorrectifier.com/catalog/1996-2006-suzuki-dr650-dr650se-stator-p-979.html?osCsid=a7d0bda81e35e5b67303dfb1f15c0bc7

They also have this advertised, though $100 for a rectifier is a bit steep for a meager 8% increase...

http://www.regulatorrectifier.com/catalog/1996-2005-suzuki-dr650s-dr650se-regulator-rectifier-p-2673.html?osCsid=a7d0bda81e35e5b67303dfb1f15c0bc7

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What they're selling is the Electrosport part number ESG430 which is a stator for a Yamaha 350 Warrior ATV. The stators are physically interchangeable but the Warrior has different plugs on the wire ends. I imagine you would have to splice your original plugs onto the ESG430 wires. I'm skeptical about their claims of higher output for the DR650. I think a stock Warrior has around 150 watts.

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