Lighting and Charging system

Discussion in 'Electrical' started by gilesthealmighty, Oct 28, 2008.

  1. hi, as requested in the white wire thread ( i'm posting my setup.

    First things first, MY white wire produces about 8v at idle, and just over 12v at half throttle, so check yours to make sure (i'm not sure why theyre so different sometimes). If you get a huge voltage i'm guessing its because of the voltage difference in the AC voltage, so use a diode, or make a rectifier like i shall explain here :)


    The rectifier is the most important bit and you can find diagrams on google but heres mine:

    Actual Thing
    Rectifier Attachment

    Side note: the switch you see on the rectifier is my anti-theft switch which is basically a kill switch, it shorts the white wire to ground so you can't start engine, and because its hidden people can't work out why it doesnt start :)

    This will produce a DC current and won't waste any of it! 4 diodes is more efficient than just a 1 diode setup (you skip one ac cycle with that)

    Charging bit

    again this is simple .. simply hooking up a battery .. BUT make sure you have an extra diode so it will charge, but NOT discharge into the engine when you press the kill switch, this would short the battery and probably melt a wire or two :p


    Lighting bit

    I can't quite remeber if i use another diode (i love these things) but i'm pretty sure i just hooked it straight up from the battery terminals .. if anyone has any problems shout and i'll check it out ..

    the battery powers a 50watt energy saver halogen (it uses 35watts enery to make 50watts light!) which i made a little housing for out of 40mm piece of straight tubing which i got from a local DIY store, and an on off button behind it :)

    Light 1
    Light 2

    Once all thats on the final thing looks like this:

    A Note ...

    I was cycling at night and the battery ran out but despite this the light managed to light very very dimly through the charging system .. i think the battery must have acted as a big capacitor and not killed the engine through shorting and i managed to make it home while being able to see! i plan on adding another light (12v 0.3w) or something ... i had one once but blew it, and it was amazing you could see clearly with no battery needed, and this could run straight off the white wire! :) so when battery dies you can still see something!

    Hope this has been useful
    Last edited by a moderator: Oct 28, 2008

  2. heathyoung

    heathyoung Member

    Nice - if you use shottky diodes, they have a lower voltage drop (less energy is lost to heat) - they may be salvaged from old PC power supplies (TO-220).

    The internal resistance of the charging coil will proabably be enough that no furthur regulation will be needed. You could probably run a 3W Cree K2 with your bridge rectifier, cap and a puck (with wide voltage capability) without the need for a battery.
  3. loquin

    loquin Active Member

    The polarity on your sketch is reversed on everything. The arrow on the diode symbol points in the direction of current flow, from positive to negative. On the physical diode, the light stripe indicates the flow 'out' of the diode.

    Attached is a 'standard' schematic of the above circuit. No 'blocking' diode is needed, as there are already diodes in the bridge rectifier which serve to keep any current flowing from the battery to the engine.

    The battery and light must be isolated from ground, as otherwise, they'll be shorting out the rectifier circuit.

    Your white wire can provide no more than half an amp. At 12 volts, that's about 6 watts of power. Hence, the reason that the light failed after a while. You were pulling more power out of the battery than you were putting in. Also, to charge a 12 volt battery, you need 13.2-14.2 volts. Since standard silicon diodes drop 0.6 volts, the white wire needs to provide 13.8 - 14.8 volts to charge the battery. (If you use schotzky diodes, they only drop 0.3 volts.) However, you do NOT want to get above (at 30 deg. C) about 14.2 Volts, at the battery. This will be above the 'gassing' voltage, which causes bubbles of gas to form on the plates inside the battery, which WILL lead to undesirable results, and early battery death. Ref Sealed Lead Acid Battery Charging Basics.

    The dashed line between the engine and the bridge rectifier represent the fact that the engine is grounded to the chassis, and if a good ground is made, this wire isn't needed, if you ground one 'side' of the bridge.

    There's another problem with this approach. If you don't use the light, but continue to run the motor (and charge the battery,) eventually, you'll be over-charging the battery, which produces excess heat, which will reduce battery life.

    Attached Files:

    Last edited: Oct 31, 2008
  4. duivendyk

    duivendyk Guest

    It appears that the CDI unit only loads the generator coil during the postive cycle of the ac output of the generator.This also shows up at the white wire output(the generator coil behaves as a step down transformer), at this output the positive going (the loaded output) is much lower than the negative going one.It might be feasible to take advantage of this circumstance and get more current&voltage out of a negative going rectifier circuit to charge a battery without affecting theoperation of the CDI unit!.To begin with the rectifier should be hooked up to a resister and electrolytic cap to ground to get an idea how much you can get out of the rectifier circuit.To that end a load consisting of a resistor to ground in parallel with a sizable electrolytic cap. a few 100 microfarad or more (25 volt rating) would be nice,with the positive side grounded.First starting with a 20/30 Ohm load resistor and measuring the output voltage and then reducing the load resistance to see if the engine complains by putting extra resistors in parallel.The stripe on the diode (negative side) has to go towards the white wire and the other side to the resistor and cap.The next step would be to hook up a battery 6 or12 V? what capacity? and refine the charging cicuit.Probably a zener diode inconjunction with an LED indicator to monitor the battery voltage and stop charging or turn on the lights when the voltage goes over a certain limit.It would be interesting to find out if or how well such a negative charging circuit could be made to work.Any fearless investigators around,willing to push the envelope?.
    Last edited by a moderator: Oct 31, 2008
  5. ZnsaneRyder

    ZnsaneRyder Member

    I'm willing to give it a try. I have a different engine, but same concept. Other difference is my yellow (white) wire outputs only 2-3V AC according to my multimeter, but I haven't tried to rectify it yet to see if I could get a higher peak DC voltage to charge a capacitor with yet. I'm interested in running LED headlights from the engine and only need 4.2V max to charge a small LI-Ion cell to run the lights.

    Also, that's interesting that the negative swing may have more output voltage.

    Have any of you checked out an electric-start engine's charging system? Most I see have a seperate coil for charging the battery that is next to the flywheel and magneto coil, and uses the same magnet on the flywheel to generate the voltage. I wonder how hard it would be to add another coil on these engines and wind your own wire on it to get the desired voltage and current.
  6. duivendyk

    duivendyk Guest

    A seperate coil for power is the usual practice,this white or yellow wire output is just a cheapy half-assed way to get at least some output.The other disadvantage is that this output is not "floating".This means that a fullwave bridge rectifier circuit has to float(no connection to the frame) and so does the battery and anything connected to it and an accidental short to ground would mean trouble
    The larger negative swing is most likely due to the CDI unit only presenting a load in the positive going ac. output excursion of the generator coil.The trick is to find out what you can load the White wire with before the ignition is starts misbehaving.
    Last edited by a moderator: Nov 2, 2008
  7. LocustsOfSteel

    LocustsOfSteel New Member

    I was thinking that if the egnition takes too much juice from the stock magneto, then that idea of upgrading the magneto would seem logical at that point....
    So, i took a look at my bike and noticed the cover for the magneto is about 1/2 an inch away from the pedals crank arm, so there appears to be about 1/3 of an inch of reasonably safe expansion space for extra coils and magnet...
    The only problem with that, is a hand wound motor might not put out as much juice as a mechanicaly wound motor.... hmmm

    I read someones idea about mounting a small 12v alternator under the engine, cutting open a hole just before the clutch, and gearing that small gear to the motor... just food for thought.:thinking:
  8. i'm in the process of adding an alternator but finding a gear the same size/teeth as the original is next to impossible, so i'm devising my own way, i'll post a thread when its done and working :)
  9. LocustsOfSteel

    LocustsOfSteel New Member

    What kind of alternator are you thinking of using, and where is it to be mounted?
    Are you thinking about the under the engine block scheme (this would theoretically produce power on idol, and would work on a bike with a SBP shifter kit), or attached to the stock drive chain (seems to be easier to install)?

    Thanks for posting your project in such detail, and with images.

    The reason that I'm so interested is that I have a 12 volt system as well, and i plan to add some kind of recharging system because i was lucky enough to get a hold of a battery booster/jumper unit that has a power output jack, and it would be nice to never have to charge the bike off an outlet and have enough charge my phone from the jack. and maybe run a CD player off of the jack just to show off lol.
    Next step would be to get the shifter kit and rearrange the sprockets so it will go over 45 without the RPM's redlining... Then i can die feeling accomplished lol!

    Also, i am working on a simple and low cost blinker system, i am also doing some research on ways to level the voltage and current from an alternator connected to a highly variable source of RPM's with simple low cost methods, i will post some clear diagrams of these systems, along with my whole wiring diagram in the next few days for community reference.
    Last edited: Dec 20, 2008
  10. duivendyk

    duivendyk Guest

    Wether you wind it by hand or not does not affect the output what matters is the number of turns and the wire size.If there is room, the best thing is to put a separate winding on the coil (put some tape in between) and hook it up in series with the white wire output.Some people have tried negative output rectifiers,there is reason to assume that the CDI unit only loads the positive going cycle of the ac. output of the generator coil ,so that the rectifier circuit would not affect the spark output,but I don't know they have any success,just stick a diode on the White wire,(the stripe side to the white wire and connect to the negative terminal of a 6 V SLE battery (not completely discharged ) via a dc. Am meter,with the positive batteryterminal connected to the frame ground,and measure thecharge current ,if any.First start engine before connecting the load.
    Last edited by a moderator: Dec 21, 2008
  11. ZnsaneRyder

    ZnsaneRyder Member

    There is two ways to use that varying voltage to charge your battery:

    1. Resistor - A series resistor will eat up the extra voltage produced, and limit the max amps delivered to the battery. Benefit: Simple and Effective, Drawback: resistor wastes extra power as heat. A 10 ohm 10W power resistor from RadioShack would do the job.

    2. Pulse Width Modulation (PWM) - a circuit that will take whatever voltage delivered to it, and output it in pulses of different length which is filtered to create an average voltage that is desired for you. The benefit is much less wasted power, and more use from your voltage range, the drawback is complexity.
    Last edited: Dec 25, 2008
  12. heathyoung

    heathyoung Member

    There is also another - a buck/boost regulator (basically pwm, but constant output voltage regardless of input voltage)
  13. duivendyk

    duivendyk Guest

    Regulators can limit the max battery voltage and thus can prevent overcharging,which causes premature battery failure,but they take extra juice of which there not all that much to begin with.There are more sophisticated battery charging IC's around (Texas Instruments makes them),they are intended to be used in conjunction with a dc. source,not the charge pulses from the rectifier circuit and probably take to much current anyway.SLA batteries can cope with the low duty factor high amplitude charge pulses from a rectifier circuit pretty well,the main problem is to limit the charge current when the battery approaches full-charge,14.5V for a 12V and 7.25. V for a 6 V battery.Chronic overcharging kills batteries.The simplest thing might be would be to light up a LED as a warning signal,this would also reduce the charge current to the battery,a Zener diode in series with a LED, say a 4.5 V one with a 3V LED might do the job.Then the charger could be switched off or the lights turned on, to kill or reduce the charge current.
    Last edited by a moderator: Dec 31, 2008
  14. HoughMade

    HoughMade Guest

    Alright you electrical geniuses- I may need to get my bike titled, so that will require an effective headlight, a brake light and turn signals.

    I do not like to do things half-arsed, so I would like to add a dynamo front hub (w. drum brake). I would like to use that to charge a battery (safely) and then run the lights off of the battery. Keep in mind that i will almost never use the headlight as i will not ride at night, so if the chargung does not quite keep up when everything on, that is not a big deal.

    BTW- I have a Honda 4 stroke so there is no "white wire".

    Please, someone tell me what I need to accomplish this.

  15. duivendyk

    duivendyk Guest

    Do you know what the reqs. are for the headlight (inspection?),do they try to make your life miserable ?.For a bicycle headlight + auxiliary lights you could prob get away with running everything off the hub generator only,unless stationary functionality is reqd.If a battery is necessary a 6V, 4.5 Ah should be plenty.
    You run the gen. output ,2 wires to a full wave bridge rectifier using 4 diodes preferably Schottky diodes,they have less voltage drop than the silicon type and hook up the pos/neg output to the battery via a switch.There should be plenty of info in the archives on how to do this.Charge current for a lead acid battery should not exceed one tenth of Ah capacity,for a 5Ah battery not above 0.5 Amp.It would be smart to get a V/A meter if you want to mess around with electrical stuff and it would be worh while checking this when trying things out.If you intend to ride at night only rarely,it's quite possible that you'll end up overcharging the poor battery and killing it in due course.If the battery voltage gets close to 7.5 V when charging you are in the dangerzone.There are ways to keep it from getting overcharged but that involves a fair amount of circuitry I'm afraid.The other approach is to just forget about the generator and charge the battery from a 6V charger at home once in a while,that would be simple&cheap.
    Last edited by a moderator: Jan 21, 2009
  16. HoughMade

    HoughMade Guest

    Thanks- a home charger is easier....never gone the easier route before.

    The Sturmey-Archer X-FDD is rated at 3 watts at 6 volts at 12 mph. Obviously I would be travelling significantly faster than 12 mph.

    The 6 volts and 3 watts equates to a possibility of .5 amps. However, I understand that the output will increase with speed, would it be a proportional increase? In other words, would double the speed double outout or would double the speed equate to something less than double the output.

    I could get a variable voltage regulator (I've not see a fixed regulator at 7 volts) to keep the voltage output to the battery to about 7 volts or so. However, that does not limit the current, but would there be enough current to worry about?
  17. LocustsOfSteel

    LocustsOfSteel New Member

    Hey HoughMade, did you say "Titled"? It's under 50cc right? If so i thought it counted by law as a motorized bicycle? Did a pig tell you that you had to?

    You could always do what i do, and use a 12v battery booster for a car to power the lights.

    A battery booster is 12v so you can use motorcycle or moped lights, it's used to give a car a jump so needless to say there's plenty of juice for hours of use, they come in fairly compact models, they generally have built in circuitry that prevents overcharging and gives you a power level reading... And best of all it's affordable.

    I'm still charging mine at home every once in a while, and that works just fine for now, but i still want to make my bike fully self-sufficient, so I'm trying to devise a way to get a pocket bike alternator hooked up to my 2 stroke engine, I'm thinking that will be installed in 1 of 2 ways...
    #1: Chained onto the jack shaft on the SBP shifter kit (I'm in the process of installing the shifter kit, so I'm not sure yet).
    #2: Mounted under the engine and geared directly to the crank (harder to install, however that would allow the battery to charge even when the bike is idling).
    I believe the only way to make that work would be to find out the max&min RPM's of the engine and/or jack shaft, and set the gearing to match the ideal RPM's of the alternator, run the power through a regulator-rectifier-buck/boost (not sure yet, need to do some more research to see exactly how they work), then into the battery's charging port.
    Last edited: Jan 22, 2009
  18. HoughMade

    HoughMade Guest

    There are proposed laws in my state that would require title and registration. They are not law yet, but if they are, engine size is irrelevant. Anyone who says there is a federal law to the contrary knows not what they are talking about. There is not. The state can make these laws if it wants to.

    I want to make something custom to fit the aesthetic design of the bike and will not use something that does not look like it would be appropriate on a pre-WWI motorcycle.

    The overcharging is my concern and I may cannabalize something like a jump starter, but I don't have the ned to go to 12 volts and the X-FDD brings me drum brakes I want and at least 6 volts which is all I need.
  19. duivendyk

    duivendyk Guest

    The voltage under load does not go up proportional to speed,but tends go up less at higher rpm.The generator is an ac source and the generator coil in which the voltage is induced by the changing magnetic field has inductance. The voltage drop across an inductance goes up proportional with increasing frequency (speed) and this drop is subtracted from the induced voltage which is proportional to speed, limiting the output to some extent, proportional to say about 0.8S above 10mph .If you are running above 15mph I think you would have no problem charging a 12V battery with a hub dynamo.Remember 10V ac implies a PEAK voltage of about 14 V. For further info go to where you can find a wealth of info on bicycle lights, dynamos etc.The 12 V battery charger might put out too much juice for comfort (a couple of Amps or so).
  20. HoughMade

    HoughMade Guest

    Thanks! Good info. Next project.