TOPIC:

inline79 wrote:

Everything seems good to me!

It'd be interesting to see it on a scope and what happens to the waveforms once you have the regulator running.

I bet you can pick up one of those humongous CRT Oscilloscopes for real cheap!

Click the link in my first post of this thread.

You're right about o-scopes. At one point I had three of them... didn't pay a penny for any of them!

dnpurdy wrote:

Physics and EE always were a great hobby for me, even a as a kid.

However, I got sucked into the "pure" side of mathematical logic.

Thanks for the 2 blub idea, that sounds just up my alley. Definitely seems like a legimate way to isolate the load ability without trying to find a way of measureing flux density!!

Here's a little write up on a project i did a couple years ago. It started one day when a voltmeter gave me a result I didn't expect. I wanted to figure out exactly what a voltmeter measured without just googling for the answer.

home.comcast.net/~loudgpz/ACvoltmeter.pdf

You might appreciate the math. (sorry if the notation is sloppy, math is not my first language )
The equations on page 18 gave me a headache.

loudhvx wrote:

....The equations on page 18 gave me a headache.

Sorry guys, this whole thread is giving me a headache.

@loudhvx -

I hooked my 6 diode bridge rectifier setup up directly to the stator output leads and started the bike up. I attached two headlights across the rectifer outputs and measured the DC potential.

I got 11.7 volts at idle.

With one blub, I got 17 volts across output.

This definitely seems to indicate that the generator is simply not outputting enough, period. Now, there seems to be two resons. Either the magnetism in the rotor is low or the stator is bad. Testing the stator per manual specs, I get no shorts to ground. Line to line, I get .9 ohms on my meter on each pair. The service manual says the spec if .48 to .72 ohms. So I'm high, but I also doubt my meters ability to measure such small resistances. Since they are all the same and since I doubt my meter is a high impedance one, I assume the stator is alright. Additional, on a visual inspection, I saw no indications of shorts or burned wires.

So that leaves me to believe the rotor has just gotten weak. Do you know a way I could verify this? Is there a decent way to find a replacement that I know would be strong enough? Can I replace the magnets myself, or do I need to replace it as a unit? Can I re-energize these magnets in any way?

Also, I know a rewound stator could increase my power by 20%. In this case, does it seem more appropriate to look to replace the rotor or will a aftermarket stator pick up my slack?

11.7 doesn't sound that bad, it actually sounds good. That means you are getting 100 watts at idle. You only need about 80 or 90 watts to maintain 12v at idle.

At 11.7v, tha means the peaks are at 12.3v (11.7 / .95 = 12.3 as per the drawing I posted earlier). So with your 100 watt load, the battery would be draining slowly at idle. With the bike's real load of about 80 or 90 watts at idle, you may be just maintaining charge. Any higher RPM would be charging the battery.

Did you check it at 3000 RPM? I believe the voltage will be rather good.

If you wanted to really check, you could hook up your home made rectifier to the battery and carefully monitor the battery voltage with a meter. Then you'll know for sure the alternator is good. If you get about 12.5 or higher at idle, and 14v at 3000 rpm , you are good to go.

Another round of tests. Here's what I got.

I put my 3phase bridge rectifier straight from the stator output, and out the +/- lines directly to the battery and started it up. Here is the test results.

1. With regular load: headlight low, front running lights, brake running light

@1,200 rpm: 13.00 V
@4,000 rpm: 13.40 V

2. With high load: headlight high, front running lights, rear brake light engaged, left turn signal jumpered to be fully constant on

@1,000 rpm: 12.50 V
@4,000 rom: 13.15 V

3. With no load: Only had the main fuse installed, only thing getting power was coils.

@1,000 rpm: 14.40 V
@4,000 rpm: 15.20 V

These all seem really low. I would have expected the no load measurements to be much much higher at 4,000 if the charging system was behaving as it should. If the reg/rect had been connected, it would have JUST engauged. to shunt to ground.

I can understand that the battery would be providing some back limitations to "no-load" test, but still.

One really strange thing I noticed that ONLY occured at idle -- the voltmeter would drop to about 1-2V for a fraction once every two to three seconds. It go right back up to 13 but it would drop again for a moment 2 seconds later. This dropping did not occur at higher RPM.

Ideas/opinions?

Post edited by: dnpurdy, at: 2007/05/28 17:20

It sounds like to me your thingamabob is going bad. Looks like your getting decent voltage and everything is ok, except the fluctuation.. I would think something is grounding out somewhere? I'm not that electricly minded, though I enjoy the subject.

It's possible you have a bad battery or bad connection somewhere (evidence by the volt meter fluctuations). Do you get those fluctuations when your rectifier is only connected to the headlight loads? Also, the readings are not real meaningful if the battery is not fully charged. A low battery can bring those voltage readings down quite a bit. Some smaller bikes use just a battery as the regulator because batteries are so good at keeping the voltage down to a 13v~15v range.

The trick is to isolate things as much as possible. The homemade rectifier and dual 55w-headlight-loads do that nicely. I would like to have seen what the voltage was on the two 55w headlights connected to your rectifier at 3000 RPM.

I'll do that when I get home from work tonight.

looking at all the testing you are doing, I follow about 80% of it and figure the rest out by reading the whole post, two questions come to mind
1 spotty charging? do you mean that the battery goes dead or looses a charge while riding?
2 have you looked into bad connections and wires, mostly corroded battery wires?

Well, the general condition is this. I can charge the battery off bike up nicely (it is brand new). Put it in the bike, the bike idles smoothly, sounds quiet and shows good voltage.

After about 5-10 miles in the city the idle continues to drop until I gotta choke it or turn idle up to stay alive.

Basically, it breaks even at about 2,000 ~ 2,500 rpms as best I can tell. It charges SOME once the rpms go up, but at idle after awhile, the voltage drops to 12.4 or so an I gotta get up to 5000 rpm just to see anything CLOSE to 13.5 charging voltage.

I have suspected wires, but the behavior occurs even with all fuses pulled but the main. I have suspected a weak rotor magnetism whereby I'm only getting the necessary charging potiential at high rpm, but am not sure.

Most of the test I'm doing is going back to first-principles on the charging system and making sure the system works part by part. My thinking was that no amount of bad wire hunting would be worth anything if the generator isn't putting out enough, so I'd rather verify source before testing down the line systems.

And yes, I have pulled all the connectors, cleaned and reclosed tightly. I have also replaced the positive battery cable, clean ground stap connection, etc. The main charging circuit has less thatn .2 V drop on both positive and negative sides, so I doubt it is a bad wire/connector issue.

Post edited by: dnpurdy, at: 2007/05/29 14:52

what you just described sounds like a bad recifier or regulator depending on how the charging system is set up some are a combo unit, its breaking down under a heat load.
weak magnets would show low output all the time I would think, its not hard to recharge the magnets but that is always a temp fix, never seems to last very long