# Battery charging for Scooter



## dutsidoo (Oct 31, 2008)

I have a scooter that simply cannot keep the regulator/ rectifier working. So I want to try to make my own. The stator from the scooter puts out about 70 Volts AC and I am not sure how much amperage it puts out, but I know from failure modes, it fries my lights when the rectifier goes out. So it has plenty of juice. I want to convert the 70 Volts AC to 13-14 volts DC.

I made a simple rectifier using a series of 4 diodes and used a 13.6 5W Zener diode and I do get 13.6 volts from my circuit. But no juice. I cannot even light a bulb with it. Looking for some suggestions. Can someone draw me a circuit to make this work.

Thanks for the help.


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## leroys1000 (Aug 16, 2007)

If I remember correctly,your circuit should be something like this.
http://img.photobucket.com/albums/v413/leroys1000/Powersupply.jpg
Sorry for the sloppy picture,but should give you some idea.
You can buy one piece bridge rectifiers that already have
the 4 diodes built in.


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## dutsidoo (Oct 31, 2008)

That is pretty much what I have, However, on the out side of the Zener diode, I do not have enough power to run even a small light. Not enough to re-charge the battery. Right now I have 4 1N5408 Diodes as the bridge rectifier, and (1) 1n5350 Zener diode. I have tried different load resistors adjacent to the Zener, but cannot get current out of the circuit.

Do I have to high resistance diodes??


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## leroys1000 (Aug 16, 2007)

Shouldn't need a load resistor in the circuit as the powered device
is the load.
Is it possible that most of your current is running through the resistor?

Also,check the drive motor and other crcuits on the scooter for a short.
There has to be a reason that it is pulling so much current that it is
blowing rectifiers.


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## dutsidoo (Oct 31, 2008)

I will try as you suggested and remove the load resistor. I'll let you know what I find. Thanks much.

One question though. On your drawing, you have 13 V located on one of the AC wires from the transformer. Should I get the 13 VDC out of the neg and pos beyond the Zener?? Just for clarification.


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## leroys1000 (Aug 16, 2007)

Yes,the transformer drops the voltage.
The output is still AC.
Didn't have space in the drawing.
The 13V ac is accross both wires.
Pulstaing DC comes out of the rectifiers and the filter capacitor
charges and dischages to fill in the drops between the pulsating DC.
The zener then maintains the votage by shunting any ovarage to ground.


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## K7M (Feb 27, 2000)

I would try your circuit using a Radio Shack rectifier assy part # 276-1185. It is rated at 25 amps. I don't think the 3 amp diodes you are using are big enough to light the lights, never mind charge the battery. Also in a charging circuit the battery acts as the capacitor, it really isn't needed on the scooter.


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## dutsidoo (Oct 31, 2008)

Attached is my drawing of the circuit I am using. Are you saying then that I should draw the 13.6 volts from the Stator wiring (Transformer) rather than from the red wire (as noted on my drawing)?


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## dutsidoo (Oct 31, 2008)

.....# 276-1185 is rated at 50 volts. The scoot puts out about 70 volts at high rev. I think I would smoke this one. What is the difference between a standard diode, and a rectifier diode? 

Yes I am a beginner.


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## leroys1000 (Aug 16, 2007)

I am still trying to figure out this stator and why you need to connect to it.
Does the scooters charger plug into the wall?
Is there some kind of generator on it.

In your picture,you don't have anything to drop the voltage down.
A recifier diode is designed to handle the higher current load
of power applications.
Stiill think you are dropping a lot of voltage accross that load
resistor and it shouldn't be needed.
Just took a look at a circuit diagram for a zener and the load resistor should go at the base of the zener,to limit current.
Put it where you have the lable 5W zener.
Where you have it will just drain power to ground.


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## dutsidoo (Oct 31, 2008)

The scooter has a generator on it (stator) it is pretty much like a car alternator. It puts out between 25 and 70 volts AC (depending upon the rpm). No, it does not plug into the wall. The scooter is gas powered. 

It is the two leads from the stator that I am getting my power. I have removed the load resistor as you suggested and I still cannot get juice. I am wondering based upon your description of the rectifer diodes vs standard diodes that I am using the wrong dioedes and need rectifier diodes. 

The Zener diode (1N5350) is a 13.6 volt Zener. It is what is dropping my voltage down from 25-70 VDC (via the rectifier circuit) to 13.6 VDC. I do get 13.6 volts out of the circuit as shown, but do not have enough juice to light a bulb.

So, To sum it up:

I am getting 25-70 Volts AC from my Stator (generator) I am running them to the the Rectifier circuit using the 4 (1N5408 diodes) this circuit changes the 25-70 Volts AC to 25-70 volts DC. Then I am using the Zener to drop the 25-70 VDC to 13.6VDC. This all works, but no juice. 

So, am I using the wrong diodes? If so, what would be the proper diodes to use?

Thanks much for the help and suggestions.


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## leroys1000 (Aug 16, 2007)

You need to drop the voltage at the AC line.
Zeners are only designed to handle minor voltage changes,not
to drop voltages.
Might have fried that already.
You are going to have problems with the kind of overvoltage variation
on the AC line.
Shouldn't have an output of more than about 14V if you want to be able to
properly regulate it.
Also,your 3Amp recitifiers are probably not going to handle the current that circuit is producing.
I,m not sure were headed in the right direction here.
Can you tell me what type or model of scooter this is.
It almost sounds like a magneto driven electrical system
that is using the 70V ac to power the lights.


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## dutsidoo (Oct 31, 2008)

I have attached the owners pdf manual, or you can go here.

http://abacus-es.net/motorscooter/ifensterl.php?http://www.oregonvintage.com/Scooter.html

It is a Tank 150 Urban Sporty. Chaper 14 you will find the electrical charging system. I simply cannot get the stock units to last. So, I want to make my own if possible.

So, what you are saying is I need to first step down the 25-70 volts AC to around 14 volts AC, then rectify it to 14VDC and then use the Zener.

What, do I use or how do I do this?

Thanks again.


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## leroys1000 (Aug 16, 2007)

You would need a 5 to 1 stepdown transformer to drop the ac.
With a 5 to 1,the max output from the transformer would be 14V.
I would suggest using a heavy duty one piece bridge rectifier in
place of those diodes.
The PIV for the rectifier stands for peak inverse voltoge.
Thats how much it can handle with polorized backwards before it will blow.
200 is plenty for this application.
Something like this...
Bridge rectifier.
Scroll down to zener diode on this page to see how the load resistor is used.
http://www.kpsec.freeuk.com/components/diode.htm


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## dutsidoo (Oct 31, 2008)

Wow, This is excellent. Where, or how do I get a 5-1 stepdown? I googled and got no where. Most go from 115 to ?? Same result with voltage regulators. Can not find any that go from 25-70 to 14. Tough to get?

I love the education and appreciate your help.


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## leroys1000 (Aug 16, 2007)

Usually,if I need something like that I check for electrical component
wholesalers in my area.
They will usually sell a part to a retail customer.
Also,radio shack usually has a catalogue order service for 
electrical and electronic components.

My question is,if the DC system on the scooter is 12V,why is
the power generation system putting out 70V?
Is there a transformer already on the bike,

Are you sure you are not working on the magneto and possibly there
is an altenator on the other side of the crankshaft?

I can't really read the wiring diagram on the page you linked.
It's too small and zooming makes it worse.


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## K7M (Feb 27, 2000)

OK let's see if I can explain this. A rectifier is 4 diodes wired in a bridge as you have wired yours. It is a convient package as it is easy to mount and you can attach it to a heat sink. You do not need to use a transformer to step down the 70v AC coming from the stator. As far as the rectifier I suggested being 50v vs 70, I would give it a try for $4.00. I have used them on motorcycles, which are pretty much the same as your scooter.


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## K7M (Feb 27, 2000)

I just looked at the schematic for the scooter and it is a 3 phase stator. the lights are fed off one of the ac legs of the stator. The charging system looks like it is wired just like my Suzuki motorcycle. I have attached a schematic of it. I hope this will shed some light as to what you have have. The output voltage between any two leads on the stator should be between 75 & 80 volts AC


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## leroys1000 (Aug 16, 2007)

OK,if your scooter is setup like this scematic and you are
using the regulator,the transformer is not necessary.
The rectifiers in this system are only half wave and not full bridge.
That drops the AC voltage by half by only passing the positive
part of the AC signal to the power system.
The negative component is shunted to ground.
The SCR (silicon controlled rectifier) and the power resistors
in the regulator drop the rest of the voltage and regulate the output.
I agree that the capacitance of the battery plates are being used
as the filter capacitor.

I think the problem you are having with current is due to trying
to connect the circuit to 2 of the output windings and they
are fighting each other.
You should connect to one of the windings for + and chassis ground for -
Don't do this until it's properly regulated.

The transformer circuit can work,but not if you are going to 
use the factory regulator.
I would use the factory regulator as it will be more stable.


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## dutsidoo (Oct 31, 2008)

Yes, the scooter does have a regulator/rectifier. Problem is (the root of the problem) they do not hold up for any length of time. And when they fail, they take alot of other components with them. Light bulbs, electric choke, voltage meter etc. This is why I want to make my own to have it hold up. 

There is a magneto, but it only runs the spark plug via a CDI unit. Totally unrelated to the Stator system (generator). I have no idea why it puts out 70 volts, but according to expert scooter mechanics, that is normal.

I'll try to find a step down and go that route. Thanks again for the help. Much appreciated.


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## dutsidoo (Oct 31, 2008)

attached is the circuit for my scooter. If I measure voltage between the white to ground or yellow to ground, I get nothing. I only get the 25-70 across the yellow to white. Is this normal? I only have two legs Yellow and white coming from the stator, the green wire goes to ground. Still a 3 phase system?

Are you saying then that I need only to use the white wire as my source of power and connect the yellow to ground??


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## leroys1000 (Aug 16, 2007)

No,it's a single phase,simple magneto system.
That auto enricher with the load resistor looks like a possible
current control.
Have any info on that.
Check to make sure the resistor is good and the fuse isn't blown.
May also be a capacitor.


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## dutsidoo (Oct 31, 2008)

You have the same thoughts I did at first. Turns out, the Auto Enricher is nothing more than an electric choke for the carburator. However, I also posed the question on a scooter blog much the same as this asking if the resistance (all it is, is a resistant coil designed to heat up when power is supplied (when the engine starts) and closes additional fuel to the system). But is looks as if the yellow wire and it are common off the stator. The Jury is out on if the coil affects the regulator or not. I do know that I have that coil running off of 12 VDC off my ignition switch and it does work and gets warm as designed. and for the record, I replaced that too....

So, Given what you see, what is my next step??


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## leroys1000 (Aug 16, 2007)

Would like to know more about the rectifying/voltage stabilization circuit.
With a magneto system,it may be possible to use a power resistor to
drop the voltage and for current control
Are there any diagrams for that?
It may just be possible to use a current control circuit with the
current power system to help keep it from blowing rectifiers.
The magneto pickup coil may be adjustable.
Moving the coil farther away from the rotating magnets can
reduce the amount of current produced.


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## dutsidoo (Oct 31, 2008)

No, I do not have any other diagrams for the system other than what is on the scooter site. Parts are cheap for the most part on making one, If anyone can supply a circuit to try, I'm game. Or, as you mentioned, protect the original from blowing.


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## leroys1000 (Aug 16, 2007)

A power resistor put inline just before the regulator should
control the amount of current going to the regulator.
Something like a 10 Ohm ,10 watt 100 Volt wire wound resistor should work.
You would probably want to get one with a mountable heatsink attached
to prevent any heat damage and have a way to mount it.
It will drop the voltage slightly,but not enought to interfere with the
operation of the scooter.
If 10 Ohms turns out not to be enough,you can always go higher,
but it should do the job.


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## dutsidoo (Oct 31, 2008)

I'll give it a try. Thanks again for your help. It has been very informative. I'll let you know the results. May take some time to get it all together and run the test.

Stand By.


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## leroys1000 (Aug 16, 2007)

OK.
Definitely interest in seeing how it goes.
Good luck.


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## dutsidoo (Oct 31, 2008)

OK, Here is the update: I put a stock rectifier back on the scooter. It seems to be knocking the voltage on both the yellow and white down to 13 and 16 VAC, (regarless of the rev level) which is what it is supposed to do. Howerver, what I think is the root of not being able to charge the battery, is that although I can measure 13 or so volts coming out of the regulator, while it is attached to the battery, as soon as I turn on the ignition (powers my lights), it drops to around 11.8-12. Not enough to keep it charged. So bottom line is that the white wire or charging circuit does not have enough to get the job done. Now, With that said, I currently am not usng the yellow wire for anything other than going to the rectifier. It is giving me 16 volts AC. Can I tap off of this using two rectifier diodes and then a Zener to get it down to 13.6 volts DC and then run that to the battery as well? Will that work?? If so, Not knowing the wattage of the stator, what would be a good starting level for the diodes??

Were getting closer......


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## leroys1000 (Aug 16, 2007)

With only 16 volts ac,you are going to want to use a bridge
rectified like the one I linked above.
You want to use the full wave for full output.
Use a power zener.
Better to go for over kill so use a 25 watt or so zener.
Remember to use the resistor in the zener circuit to
make sure it has proper bias voltage or it wont work right.

Might,at sometime,want to have that magneto pickup coil(stator)
checked.
Might also be a condensor in there with it that might be bad.
Even though it's not shown on the scematic.
Both shoud be under the rotor(flywheel) on the side of the scooter.
Probably take a puller to get it off.
Don't lose the keyway key.


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## dutsidoo (Oct 31, 2008)

Will do on the recitifier circuit. I have had the stator off a few times. Clean and simple. No condenser.

I'll be out for the rest of the week, but will get a 25W Zener on order.

Thanks again, Hope it works


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