Topic: Erratic Voltage

[spectre]

Bike with ignition on has consistent volts.

Bike when started has consistent voltage but after a minute voltage quickly goes up & down and sometimes by 2-3 volts.

Is that stator or rectifier typically? What keeps volts consistent?

[beemerbum]

That would be the voltage regulator I believe.

[scottly]

Are you using the stock mechanical regulator? If so, the reg switches modes from full charge current to half current to off, which can cause spikes in the voltage when read with a digital meter, especially when using a lithium battery. 

[spectre]

Ricks for lithium battery.
Odd part is it initially was working as it should. 30+ runs.

What I don’t know is why after a minute of bike running it starts to go extremely erratic.

[scottly]

Check all battery  and regulator connections.

[newday777]

spectre
Welcome aboard the forum.
You have started 3 different topics, I read through all to try to get full information as you have not given full information about what your bike is at the beginning. I'm not trying to give you a hard time, just trying to figure out what the missing pieces are to the jigsaw puzzle pieces you have scatter thrown, in the few words you put in each post you've made(you should have started telling of what year and model bike it is, what modifications on it, i.e. m-unit, what battery, what harness- is it the stock harness or totally new custom wiring. We want to help you, but with your apparent custom wired M-unit bike your problems seem tied together to me. Keep it all in one place as we cannot see your wiring when it's about the M-unit. Starting a new topic is not good progress on your part. I know you are new here and it sounds like the bike is a new venture to you(?). (I've sent a request for a mod to move you 3 started topics together because of missing information in each).
Electrical problems are hard enough to diagnose in person when you haven't done the work, trying to figure it out remotely, especially in custom applications....impossible without full disclosure on your part and not scattered about in different places. Keep the wiring problems together in one place until you have it running properly.

Here are your threads you started
http://forums.sohc4.net/index.php?action=profile;area=showposts;u=58598

[newday777]

And please.....Don't assume anyone can remember all your information.

[spectre]

First thread was about tach pick to gauge, not related. Second is about a cause for shut down of munit which I received some great insight, still having discussions and had mentioned erratic voltage, even with a large battery. Move if you need to, in this case both previous posters gave me what I was looking for so I appreciate that.

[TwoTired]

Bike with ignition on has consistent volts.

Bike when started has consistent voltage but after a minute voltage quickly goes up & down and sometimes by 2-3 volts.

Is that stator or rectifier typically? What keeps volts consistent?

Where are you taking measurements?  At the battery terminals or elsewhere?  The battery typically irons out transients due to its massive capacitance.  What size battery do you have?  Smaller batteries allow larger transients.  The battery voltage should dominate the bikes system voltage if the wiring distribution is properly up to the task.

If you are starting with electric start, the battery will lose full charge due to extra load. The charging system will try to restore charge aggressively at first and when near charge restoration will no longer try as hard, telling the alternator to back off to protect the battery from overcharge.
 This assumes your regulator knows what voltage is correct for your battery and your battery is in good condition.  Battery full for lead acid is > 12.7v. Battery full for lithium is >13.2V.

Does your regulator know you have a lithium battery?
Do you know your battery is still working like new?

Forget trying to blame the stator, unless you see bullet holes or axe marks in it.

Cheers,