Final explanation of scooter charging circuit By peachy (Read 738 times)

[peachy]

I badly need an explanantion of every part in the charging circuit and what it does.

I've seen a few different scooters, and some of them have just R/R's, some of them have R/R's and a little metal box with just one wire going into it, and some of them have two metal boxes, and one had a little black box with four pins and yellow and white wires

It's just ridiculously confusing and I can't find anything on the internet that doesnt explain what i already know

Here's how i understand it. We have the stator, it makes ac power when the engine runs, this goes to the R/R to be turned into DC. Because the AC voltage rises with the revs, the R/R has a zener diode or something inside it, --as well as a (full bridge? half wave?) rectifier-- that gives a dummy load when the revs and AC voltage goes up, dropping the voltage (does it load the AC circuit? Or the DC circuit after it's rectified?) so that we have a steady 14.6 volts for the battery to charge on, and to run the lights, etc.

Here's a few things i dont get
1. Why on earth would a new battery show 15v DC, with nothing connected? Is it a problem with my multimeter? Is it because it's (the battery) new?
2. To tell if it's charging, i would assume when the battery is connected to the charging circuit, the voltage goes up as you rev, to, prefarably 14.6 V, but what would it be if the battery voltage was higher? should it go down because the diode activates? Would it go up more, to say 18 vDC beacuse they add or something? (i once measured that on high revs)
3. what is the purpose of those metal boxes? are they spare doiodes? Are they for the lights? What the heck do they do? I opened one and it was just a wind of (probably resistor) wire around a glass core. The engine runs without it, and the battery appears to charge as well.

I have a reasonable amount of understanding about electrical principles, etc. but if i dont know what a thing does, then i cant tell why/if its broken. and I'm worried I'm gonna mess something up or blow something working in the dark like this.

Thanks,
Peachy

[JR]

peachy

1. Why on earth would a new battery show 15v DC, with nothing connected? Is it a problem with my multimeter? Is it because it's (the battery) new?

Could be either, I would test the battery with another meter and by doing that without buying a new one you could get it checked at a auto parts place for free. If it does register 15Vdc I would then rig a 12 volt light to it and let it run down to completely dead and then slow charge it for 8 to 10 hours, slow meaning 2amps or less. After charging it let it sit for at least one hour then test it, 15 volts or higher means something is wrong, at the most one wants 13.5Vdc.

2. To tell if it's charging, i would assume when the battery is connected to the charging circuit, the voltage goes up as you rev, to, prefarably 14.6 V, but what would it be if the battery voltage was higher? should it go down because the diode activates? Would it go up more, to say 18 vDC beacuse they add or something? (i once measured that on high revs)

The stator consists of a few coils of wire. The spinning magnets in the flywheel interact with the coils to generate A/C current. The current then flows to a rectifier, which convers it to useable D/C current. Most rectifiers also act as regulators. The regulator will control how much current flows to the battery. At high engine speeds and low electrical loads, more current will be generated than can be used. Usually excess current flows to the battery to recharge it, but too much current will wreck the battery. In this case, the regulator will re-route the current to ground.

It's highly possible that the regulator is out and not (shunting) the excess voltage to ground thus the battery at 15Vdc? No way you should get 18Vdc if at this level very long you'll wreck the battery and even start burning out bulbs.

3. what is the purpose of those metal boxes? are they spare doiodes? Are they for the lights? What the heck do they do? I opened one and it was just a wind of (probably resistor) wire around a glass core. The engine runs without it, and the battery appears to charge as well.

I need two things, make and model of scooter and a picture of this "box" it's possible it's load resistor for the lights. Some of the older scooters have a on/off headlight switch and when the lights are off the load resistor keeps the voltage down on the R/R so that it will not overcharge and burn up the battery. With the lights on there is enough load on the charging system to not cause damage.

JR

[peachy]

Thanks a lot for your answer

Here's a picture of one of the boxes I'm talking about, it was on a Yamaha Invader 100cc quadbike, which was not charging, according to the client, and the original battery was dead.



There was also a SYM/Honda Duke 125cc which had two, a smaller one and a bigger one. I think it's more likely that they are something to do with the lights.

I think I'm gonna have to find a new multimeter, because the current one is pretty old, seems like the DC section is a bit iffy. The ac section works though; reads about 20-30 volts ac at engine idle, which is I believe correct

I'll be at work again on Friday . I started to work at a little scooter/quadbike repair shop recently, and I'm the most learned (relatively) in the electrical side of things. Something still feels off about that Yamaha, and a few other bikes came in with dead batteries too, so I want to be clued up about these things ?

Thanks again,
Peachy

EDIT: another thing, the box for the Yamaha has two wires coming out,
All the rest have just one wire

[JR]

Light load resistors for sure. Looking for manual.

JR

[peachy]

Ahaaa, that makes sense, because it seems that the scooters that haven't got the little boxes lights turn on without the engine running, ie. they run off the 12v circuit

[JR]

Jan 27, 2016 0:25:53 GMT -6 peachy said:

Ahaaa, that makes sense, because it seems that the scooters that haven't got the little boxes lights turn on without the engine running, ie. they run off the 12v circuit

Partly correct. Very few scooters have the lights run off the 12Vdc circuit but those that do have very good charging systems. The load resistor for lighting on scooters that run off the R/R charging system will have a on/off light switch along with the dimmer switch. Now with that said the output of the R/R is sometimes helped by keeping a balanced load on it, thus the head/tail lights. But with a on/off headlight switch in the OFF position the load in greatly decreased thus the R/R in lots of cases can't shunt all the extra charge voltage to ground. In this case the on/off headlight switch is actually a two way contact switch, when you turn the lights off you actually just switch the current output to another set of contacts to the what?........... the "load resistor" the resistor gives the same load as the lights do thus not letting the excess voltage do damage to the battery.

If you decide to remove the resistor then you need to fix the headlights so they have to be ON all the time. If not then your going to fry the battery.

JR