Help with running both a DC and AC system on Dual Sport

[OaklandF4i]

First, I am an electrical naivete.

The Bike is an XR400R with an aftermarket 200w stator that has two lighting coils of 100w each.

One 100w lighting coil is wired for my race light with an AC regulator, both AC Reg and Light grounded to frame.

The other 100w output is wired to a Baja Designs regular/rectifier. grounded to frame - no battery. The rectified DC power is for my led tail/brake light, rear blinkers, Trailtech endurance computer, and powered Amps Rugged mount for my Montana GPS.

I am trying to run this system without a battery. The Amps Rugged mount can run off 10-50v according to its specs. There is plenty of available power even at idle...

The problem I am having is the BD designs Reg/Rec doesnt seem to like the the seperate/second AC side of the system for my headlight grounded to the frame at the same time.

When I ground the AC side of the system to the frame, the Reg/Rect DC voltage output drops from a strong 12.5+/- volts at idle to below 10 or less and more so as rpms increase. If I disconnect the AC headlight system side ground, the Reg/Rect works as designed with little voltage fluctuation through out the rev range. Its not load related, happens with no DC load as well.

Questions:

So the AC systems ground is obviously affecting the DC side reg/rect using the frame as a common ground. To someone more familiar with electrical, this might be duh... yeh. Can you explain how/why this happens?

I obviously need to isolate the two systems grounds. If there a way to do so without a battery or capacitor?

I have read I may need to "float" the DC systems ground. Ie use a battery and ground the DC side to the battery and only the battery (or capacitor). Is that correct and will that work? I like the idea of a capacitor over a battery. Would that work and how do I figure out how large a capacitor it would need? Then again, the Baja Designs or even Tusk dual sport kit battery is cheap.

Are there other solutions? Am I missing anything?

Thanks in advance for helping to shed light on my limited electrical knowledge. :thumbup

 

[dmfdmf]

I'm not sure how this is wired up or what your goal is by doing this but a couple of comments (from an ME not EE so I could be wrong). I assume this is a permanent magnet generator with two phases. One phase you want to keep as AC to drive the headlights and one phase you want to convert to DC to run some DC loads. When you connect them together via the frame things get whacky (a technical term).

I don't think there is such a thing as AC "ground" like a DC system. The AC system should not be grounded to the bike, as you suspect, you need to isolate it with its own return wires. When you connect them together (via the frame) the two phases of electrical output are coupling through DC system which is reducing the output.

On the DC side, running an R/R without a battery will damage the system. I'm not familiar with the Baja Designs R/R so maybe that regulator was designed to run battery free, I don't know. If it normally has a battery then you will need a battery for it to work right. If you are doing this to save weight and kick start the bike then you don't need a big, heavy standard motorcycle battery for the starter and a much smaller one would work. What amperage and load rating are more difficult questions but it would have to be large enough to run the DC loads for a few minutes without discharging it or drawing too much current.

Why don't you explain what you are trying to achieve and what the electrical design of the bike was before the mods.

 

[Junkie]

Why not convert the whole thing to DC?

 

[OaklandF4i]

I'm not sure how this is wired up or what your goal is by doing this but a couple of comments (from an ME not EE so I could be wrong). I assume this is a permanent magnet generator with two phases. One phase you want to keep as AC to drive the headlights and one phase you want to convert to DC to run some DC loads. When you connect them together via the frame things get whacky (a technical term).

I don't think there is such a thing as AC "ground" like a DC system. The AC system should not be grounded to the bike, as you suspect, you need to isolate it with its own return wires. When you connect them together (via the frame) the two phases of electrical output are coupling through DC system which is reducing the output.

On the DC side, running an R/R without a battery will damage the system. I'm not familiar with the Baja Designs R/R so maybe that regulator was designed to run battery free, I don't know. If it normally has a battery then you will need a battery for it to work right. If you are doing this to save weight and kick start the bike then you don't need a big, heavy standard motorcycle battery for the starter and a much smaller one would work. What amperage and load rating are more difficult questions but it would have to be large enough to run the DC loads for a few minutes without discharging it or drawing too much current.

Why don't you explain what you are trying to achieve and what the electrical design of the bike was before the mods.

Thanks :thumbup

Its a kick only bike. Original system with OEM stator was AC only. The OEM system had only one lighting coil 85w with an AC regulator that powered a headlight and tailight, all grounded to frame.

New system has rewound stator with two lighting coils of 100w each (200w total). The new stator was installed primarily to power a 100W offroad light on one of the 100w lighting coils outputs via AC. The other other lighting coil is being used to power the rest (tail, blinker, speedo) and being regulated/rectified to DC primarily to provide power for the GPS.

No need for a battery for a starter. The only other reason (besides floating ground) I am aware of to use a battery is to provide power at low rpms and high draw situations when a bike doesnt provide enough power for all bikes components. Neither are applicable in this application. This system provides far more power even at idle than all draws combined.

So trying to keep the system simple and gain an understanding of why a common ground with AC and DC affects the DC reg/rect output as a learning process and

And figure out the simplest way to either float the AC or DC systems ground to separate the two.

I suppose I could buy a more powerful reg/rect and combine both output coils run everything on DC in a 200w system, or replace the AC reg with a second reg/rect to run the race light on second DC system.

But I already have these components, and separate output coils are nice for redundancy purposes in desert if one goes bad. Headlight is only critical component to get home being powered by either system.

I think it would also be simpler to float either one of the systems grounds. I have no idea how to float the AC system ground (or if thats possible). I am only aware of either a battery or capacitor to float the DC side.

Hope that makes sense with my limited knowledge.

Why not convert the whole thing to DC?

Would need a larger DC reg/rect than the Baja Designs I have (I think... could be wrong). I think it would be more expensive than their $30 battery to float the DC ground. And I would lose redundancy of the dual output. May have to go that way.

I'm learning.... :laughing

 

[OaklandF4i]

Is it possible to float the AC side and if so how? Or best way to float DC side?

 

[Cabrito]

I'm even more of a Luddite than CJ, but if you do end up running DC all the way around I've been using this one on my XR4 as an upgrade from my original Baja Designs small battery. It's a bit beefier and I zip tied mine inside the airbox. This one has a second output on the battery that I run direct to my GPS.

https://www.trailtech.net/040-batt3-7

 

[madsen203]

I'm even more of a Luddite than CJ, but if you do end up running DC all the way around I've been using this one on my XR4 as an upgrade from my original Baja Designs small battery. It's a bit beefier and I zip tied mine inside the airbox. This one has a second output on the battery that I run direct to my GPS.

https://www.trailtech.net/040-batt3-7

View attachment 506773

I have one of these inside the YZ. It's zip tied to the bottom of the seat above the air box. It works pretty well but I think the battery is getting older from being depleted so often. It's not crazy heavy and provides enough juice to keep things running smooth.

It has a slip on connector so when you pull the seat and forget it's there it doesn't yank the wires.

Similar to this:

 

[Cabrito]

I have one of these inside the YZ. It's zip tied to the bottom of the seat above the air box. It works pretty well but I think the battery is getting older from being depleted so often. It's not crazy heavy and provides enough juice to keep things running smooth.

It has a slip on connector so when you pull the seat and forget it's there it doesn't yank the wires.

Similar to this:

Michael, you know what's funny? I use that same connector on mine, but different setup. That's ham radio stuff right there. Are you a hammer?

 

[madsen203]

Michael, you know what's funny? I use that same connector on mine, but different setup. That's ham radio stuff right there. Are you a hammer?

Wish I could claim it as my own but alas I cannot. It came on the bike...but I do like the connectors. A simple zip tie holds them tight when I don't want them to separate. It's a twofer!

 

[ST Guy]

What does the ignition system run on? AC or DC?

If DC, then I'd be inclined to make the whole bike DC. If AC, then I'd be inclined to isolate or float the DC side.

 

[RVFRick]

Michael, you know what's funny? I use that same connector on mine, but different setup. That's ham radio stuff right there. Are you a hammer?

I recognize those from my server rack design days. Clever, simple and they ganged together. I believe they are Anderson Powerpole connectors. Rated for high amperage 30-350 amperes.
http://www.andersonpower.com/us/en/products/powerpole/index.aspx

Just sayin'

 

[OaklandF4i]

What does the ignition system run on? AC or DC?

If DC, then I'd be inclined to make the whole bike DC. If AC, then I'd be inclined to isolate or float the DC side.

CDI and coil is unregulated AC off a separate (third) output from the stator grounded to the frame underneath the tank. Interestingly enough, that AC circuit grounded to the frame doesnt seem to bother the DC reg/rect. I assume its because its a much lower powered AC circuit?

Can anyone explain the physics of why a common ground between AC and DC forces the DC reg/rect to lower its output?

Any suggestions simple floats of either system?

 

[ST Guy]

If the stator has three circuits, then I'd be half tempted to have all three rewired identically to put out as much current as possible. Then run a high quality VRR and convert the ignition and main lighting to DC. More work, though.

 

[dmfdmf]

No need for a battery for a starter. The only other reason (besides floating ground) I am aware of to use a battery is to provide power at low RPMs and high draw situations when a bike doesn't provide enough power for all bikes components. Neither are applicable in this application. This system provides far more power even at idle than all draws combined.

That is only one side of the coin. The battery also buffers (i.e accepts) extra power when the generator output exceeds demand. Assuming the R/R is a shunt type, normally the shunt will dissipate extra power as heat (which is why R/Rs have cooling fins) but it can't always keep up. Without a battery (or a capacitor I suppose) there is nowhere for the excess power to go other than into the loads (lights, gps, etc) or into the stator, too much excess power and it will fry these components.

So trying to keep the system simple and gain an understanding of why a common ground with AC and DC affects the DC reg/rect output as a learning process and...And figure out the simplest way to either float the AC or DC systems ground to separate the two.

You have two phase AC power, if you cross connect them, i.e. "ground" them to the frame, since they are at different phase angles (i.e. different timing of their power peak), they start driving each other instead of driving the load. One system will have to be isolated. Stators can be wired in a number of different ways. How many wire outputs does the new stator have, 4 or 3? This will determine your options.

 

[HeatXfer]

What about using a capacitor as a substitute for the battery? If all you need is a power "soak" will a properly sized cap work? They're smaller & lighter.

 

[OaklandF4i]

That is only one side of the coin. The battery also buffers (i.e accepts) extra power when the generator output exceeds demand. Assuming the R/R is a shunt type, normally the shunt will dissipate extra power as heat (which is why R/Rs have cooling fins) but it can't always keep up. Without a battery (or a capacitor I suppose) there is nowhere for the excess power to go other than into the loads (lights, gps, etc) or into the stator, too much excess power and it will fry these components.



You have two phase AC power, if you cross connect them, i.e. "ground" them to the frame, since they are at different phase angles (i.e. different timing of their power peak), they start driving each other instead of driving the load. One system will have to be isolated. Stators can be wired in a number of different ways. How many wire outputs does the new stator have, 4 or 3? This will determine your options.

Stator has 8 wires if you include the 2 for the pulse generator. 2 direct to CDI, and 4 more (2 each for each of the two lighting coils).

 

[OaklandF4i]

What about using a capacitor as a substitute for the battery? If all you need is a power "soak" will a properly sized cap work? They're smaller & lighter.

Good, question. I'd like to know. Will a capacitor work for also floating the DC ground?

 

[dmfdmf]

Stator has 8 wires if you include the 2 for the pulse generator. 2 direct to CDI, and 4 more (2 each for each of the two lighting coils).

What does the "pulse generator" do? Is that for ignition timing or crankcase position? Also, I assume the CDI means "Capacitor Discharge Ignition". Do these work together for the ignition (and independent of the power coils)?

The good news is that the 2 phase power outputs are independently wired so they can be isolated from each other. But I still need more info.

 

[OaklandF4i]

What does the "pulse generator" do? Is that for ignition timing or crankcase position? Also, I assume the CDI means "Capacitor Discharge Ignition". Do these work together for the ignition (and independent of the power coils)?

The good news is that the 2 phase power outputs are independently wired so they can be isolated from each other. But I still need more info.

Yes to both

 

[dmfdmf]

If I understand it all (and I probably don't) I would use one of the 100W AC circuits (wired directly not grounded to the frame) to power the aftermarket headlights and use the other 100W AC circuit to power everything else bike related as it was designed.

I would use the Baja Designs AC regulator on one circuit to the headlights assuming these will draw a significant amount of the 100W available. And use the 85W OEM AC regulator [See Note Below] on the other power leg and use that to power the misc. loads like tail lights, brake lights, & etc. grounded to the frame as designed. Since the headlights would be on the other circuit it won't draw more than the 85W rating of the OEM regulator (but do the math to be sure).

Most electronics like your GPS can accept a range of DC volts on the input. You'll need that info plus its typical current draw when in use. These should be available in the specs. Find a small battery, maybe for a portable drill or RC model car or a drone that has an acceptable operating voltage that the GPS can use and an Amp-Hour rating that will insure the GPS will operate for much longer than any trip or run you might make (with extra margin). Wire the battery separately to the GPS plug and mount it somewhere so it is easy to remove or charge it on the bike (using normal AC powered transformer from the house). These batteries are deep draw, don't weigh a lot and can probably power the GPS for days with a full charge. You'll need to do more math.

NOTE: After thinking about it, you might actually need a 100W regulator, instead of the 85W OEM even though the loads are lower, if it is a shunt type regulator it has to be able to dissipate most of the power generated.