DC Voltage Drops While Running

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blaat!
Posts: 252
Joined: Thu Aug 25, 2011 4:31 pm
Location: Massachusetts

Re: DC Voltage Drops While Running

Postby blaat! » Sun Aug 06, 2023 1:42 pm

Hi Jordan,

Up and down with engine revs makes sense to me, but frequency should be independent of the regulator (because it is before it, and can be tested disconnected from the regulator), no? I'm not familiar with inverter type.

Anyway, let's say 1,500 RPM x 4 poles x 60Hz would equal 360,000. That seems way high :) Residential AC voltage in US households is 60Hz

Boy I wish I knew more about electronics :(

mrkprsn,
Yeah it is a brand new conventional lead acid 6V 13Ah battery. I had trouble with a couple of the cheap sealed lead acid batteries which lost a charge quickly (even though amp hour rating was high) so I went with a new conventional. I might have ruined the SLA batteries by draining them too far, and I recently upgraded my trickle charger because the old one continued to charge even after the battery was fully charged. Anyway, this battery goes right back to 6.3V when the bike is turned off again so it seems to be holding a charge fine.

Agree, testing the voltage at the (ignition) coil might show it dropping more. I also tested at the battery and it dropped while running, just not as much. More like 6.2V instead of 6.1V at the coil. Either way, it didn't go up as I would expect it to while running. All of this with no lights on.

How do I individually test each of the yellow AC wires? Positive multimeter lead to one yellow and negative lead to a ground? Or do I just reverse the multimeter leads to the opposite yellow wires? To test voltage so far I connected one multimeter lead to each yellow wire with the bike running off the battery and got 24V-42V depending on RPM.

There IS continuity between the yellow wires, and there IS also continuity between each wire and ground, which I understand is by design:
stator-1.JPG

One question I have: Does the 6A coming from the stator mean that the bike is drawing 6A, or does the stator always output its max amperage and the regulator throws off the excess power as heat?

One more test I plan to do is reverse the polarity of the inline ammeter coming from the stator and make sure it reads zero. If the ammeter is bi-directional, could the power be flowing TO the stator instead of from it? Maybe the stator is drawing power by grounding out in a way that isn't by design... like a fault.

Heading out to a local Italian car and motorcycle show :D so will test later if I have time.

Edit:

Ugh. motorcycle show was postponed but I didn’t see it on social media so I rode all the way over there (different bike) for nothing on a beautiful day. What a tragedy ;)

Bill I disconnected the ignition switch and jumped it out with no change. Appreciate the suggestion. Keep them coming.

Also, I tested the ammeter on both yellow stator wires, and with the ammeter polarity reversed too. Four possibilities and I get just over 6 amps in every case.

Scratching my head :?:
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Jordan
Posts: 1398
Joined: Fri Dec 24, 2010 11:29 am

Re: DC Voltage Drops While Running

Postby Jordan » Sun Aug 06, 2023 11:36 pm

> Anyway, let's say 1,500 RPM x 4 poles x 60Hz would equal 360,000. That seems way high :) Residential AC voltage in US households is 60Hz

You are right. To convert from rpm to Hz, it should be divided by 60, not multiplied.


> Boy I wish I knew more about electronics :(

Me too. :)

blaat!
Posts: 252
Joined: Thu Aug 25, 2011 4:31 pm
Location: Massachusetts

Re: DC Voltage Drops While Running

Postby blaat! » Mon Aug 07, 2023 12:11 am

100 Hz makes more sense Jordan. Maybe this is the problem since I'm getting 350-400 Hz?

Below might be some actual, useful, troubleshooting info now :lol:

I decided to simplify and isolate as much as possible. Since the bike/ignition coil will run off the battery, I can have the motor spinning (a.k.a. running) with the stator disconnected and no regulator/rectifier.

I decided to test all three regulator/rectifiers, one at a time, but I only connected the yellow AC stator wires from the bike to each regulator/rectifier, and hooked the DC output up to the multimeter... not the bike.

Below are the results.

Stock regulator:
IMG_6024.jpg

Electrex World/Lacey regulator:
IMG_6023.jpg

knock-off 6V Honda regulator:
IMG_6019.jpg

Thoughts?
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Jordan
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Joined: Fri Dec 24, 2010 11:29 am

Re: DC Voltage Drops While Running

Postby Jordan » Mon Aug 07, 2023 1:24 am

Can you do sketches showing how the regulators are wired up to the bike's system?

mrkprsn
Posts: 76
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Location: Virginia, USA

Re: DC Voltage Drops While Running

Postby mrkprsn » Mon Aug 07, 2023 1:37 am

I tried looking for an explanation of how many AC cycles a motorcycle generator makes and I couldn't find an answer. Since were speaking in seconds at (1000 RPMs) or 17 RPSs I would think the equation is 17 X (4 windings) = 68 cycles/second. At 5000 RPMs it would be 340 cycles/second. i would like for someone to tell me how I'm wrong.

Even though the battery checks out I would still load test it.

I tested two of my bikes. A 200 GT and a NC Sebring. Both tested the same. Between yellow wires was .8 Ohms and each yellow showed continuity to ground.

If you're testing voltage it doesn't matter which lead you use on which end. If its reversed the multimeter will show a negative sign. I don't know if it makes a difference with Ohms.

I don't think your stator is drawing 6 amps form the battery through the rectifier. If you're stator is making 6 amps (x 6 volts) that's 36 watts. At idle not bad.
Last edited by mrkprsn on Mon Aug 07, 2023 3:26 am, edited 2 times in total.

blaat!
Posts: 252
Joined: Thu Aug 25, 2011 4:31 pm
Location: Massachusetts

Re: DC Voltage Drops While Running

Postby blaat! » Mon Aug 07, 2023 2:21 am

Here y'go Jordan
stock.jpg

ew.jpg

ko.jpg


mrkprsn,
Resistance between the yellow wires on mine is about 0.6 Ohms
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mrkprsn
Posts: 76
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Location: Virginia, USA

Re: DC Voltage Drops While Running

Postby mrkprsn » Mon Aug 07, 2023 3:26 am

That's a wide range of voltages 3.6 to 45 vDC. Can you try those voltage tests and use the frame as the ground and not the rectifier.

veloduke
Posts: 175
Joined: Sat Jul 27, 2019 5:16 pm
Location: Glos UK

Re: DC Voltage Drops While Running

Postby veloduke » Mon Aug 07, 2023 7:42 am

I think your problem may be with the stator that you are using where each of the yellow wires is connected to ground. This is obviously OK with the standard reg/rec as it was designed like that, but using a modern reg/rec is different depending on its design.

Essentially if you are putting a full wave bridge rectifier(!) across the alternator then you will lose half the power with your current alternator because the coils are connected to ground.

What I think you will need to do is either find a later alternator where the coils are not connected to ground, or disconnect the ground in your current alternator.
Your yellow wires will be connected in the alternator using a tag screwed to the alternator plate. Remove the connection to ground, but leave the two ends joined together and insulate them.

There are alternators with two yellow and one red wire - these are OK as the coils are not connected to ground, and you use just the two yellow wires, leaving the red one disconnected.
Cheers

Max

Dave354
Posts: 91
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Location: Cornwall

Re: DC Voltage Drops While Running

Postby Dave354 » Mon Aug 07, 2023 8:09 am

Hi, they don’t call it ‘electrickery’ for nothing! I had very similar issues with my nc Sebring. Regardless of rectifier type it never kicked out enough to charge the battery. I think it was breaking down under load somewhere in the stator coils but could never find the source.
I decided to go for the electrex full package from Nigel and that has fixed the issue. My old stator is now a paper weight.

As a thought, do you have a good earth ground to the engine from the battery? Something as simple as a corroded or poor earth will prevent the current getting back to the battery?
Good luck

Dave
Sebring 350 based Ducati
Triumph Tiger 1200
Cornwall, UK

blaat!
Posts: 252
Joined: Thu Aug 25, 2011 4:31 pm
Location: Massachusetts

Re: DC Voltage Drops While Running

Postby blaat! » Mon Aug 07, 2023 11:52 am

mrkprsn wrote:Can you try those voltage tests and use the frame as the ground and not the rectifier.

The rectifier component is bolted to the frame, or otherwise grounded in each case.

If I understand correctly, you are saying to connect the green/ground wire from the rectifier to the black wire of the multimeter AND the frame, and test all three again?

Interesting idea.


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