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SP2 battery charging issue

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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 01:16
Originally posted by Brian UK Brian UK wrote:

Originally posted by tomgudgeon tomgudgeon wrote:

I'm thinking now, in theory, can I leave the red and the blue wire off for the battery to actually charge?

No, I think it needs the red wire as a reference. The blue one won't matter.


I think what this actually does is power up the electronics in the regulator. The transistors need Voltage to start working. So yes the red or red/black to ignition switch is essential.

I agree the blue is merely a switch (a transistor most likely) that just turns the light on and off. If so, it won't like being connected direct to battery positive or ignition switch output.


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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 01:22
Originally posted by tomgudgeon tomgudgeon wrote:

However at low revs (engine idle) the voltmeter shows around 11 volts and the light comes on.
At higher revs the light goes off but the voltmeter only shows around 12 volts.

This means the system is working, but it's not generating enough electricity to charge the battery.


What exactly is "higher revs" (i.e. rpm)

(No won't charge at idle. This is normal.)

What's the Voltmeter? Spada dash Voltmeter? Have you got a more accurate multimeter to use?



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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 01:24
Appendix: yes could be the croc leads are not letting enough current through if you're using them to connect alt to the battery, and causing a Voltage drop

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 07:47
The onboard voltmeter is a very inaccurate device, and it's also on the end of a long wire, which in turn is across another circuit with a load. All these tend to make the voltmeter read low. You would probably see considerable fluctuation when you put the brake light on.
Best to check across the battery terminals with a multimeter.
What is your tickover set at? On my SPIII it was set at about 1000, and the light was on. This gave me a problem at an MOT because the tester left it on tickover for some time. Then we had a problem with the rear light dimming with the indicator, all due to the battery discharging.
I raised the tickover to 1100 and everything was much better.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 17:33
Originally posted by Brian UK Brian UK wrote:

You would probably see considerable fluctuation when you put the brake light on.


Indeed, and I used this to checked my brake bulb still worked when riding. LOL

Perversely, the last such dash Voltmeter I tested compared quite well against my Fluke DMM.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 17:35
Actually the voltmeter is quite accurate, it's the wiring which causes the inaccuracy.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 23 Oct 2019 at 17:41
Yes, I'd just thought of that. Big smile


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Post Options Post Options   Thanks (0) Thanks(0)   Quote tomgudgeon Quote  Post ReplyReply Direct Link To This Post Posted: 16 Apr 2020 at 13:45
Hi Guys

I'd just like to conclude this issue by saying I never figured it out.

It could have been my new wiring or a faulty stator or Reg/rec. I have no idea.

I ended up just buying a new charging system (stator and rec/rec).

It was expensive but I heard that old Guzzi's never charged properly and with my new M-unit and looms, the new system just plugged straight into the battery terminals without the need for an idiot light.

So I saw it as an investment in the future workings of the bike.

Works like a dream now and charges perfectly.
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