Hub Wheel as generator for Trike's DC power

Discussion in 'Introduce Yourself' started by MajorLord, Nov 6, 2015.

  1. MajorLord

    MajorLord New Member

    Hi! I am building a Schwinn Meridian Trike using a Straton gear kit and a Honda GX35 engine. In the old days, wheel bike hub motors were DC magnet motors, but with the new units out there, I am not sure if they are AC motors fed by their controller. The issue is that I would like to replace my existing front wheel with a Hub motor wheel, to be used as a generator to power the bike's electrics. Will any of the current Hub Wheels out there generate DC or AC, from rotation? If I can find a simple magnet motor wheel hub, I can use it for a generator, regenerative braking, and a power assist on the trike ( Still a work in progress, but coming along nicely) hub generators for light bikes are designed to run very low power LED headlights, so they are not really ideal for battery charging.

  2. KCvale

    KCvale Motorized Bicycle Vendor

  3. bigbikeseat

    bigbikeseat Member

    I have a lot of experience with what you are writing about. The front hub generator will only produce 6 volts, with a small DC current. Since it is a AC generator, you will need a bridge rectifier, and capacitor to convert it to DC. Then a 6 volt zener diode will be used to keep the voltage constant at 6 volts. I found it a lot cheaper to use a 15 amp lithium battery, and charge it up in the house. It goes a long way. The generator hub will cost around $75 to 100 bucks. Then you have to buy the rim which is about $35 bucks. Then you have to take it down to the bike shop and have it spoked up to the rim which is another $150. I usually carry a smaller second battery as a reserve in case the 15 amp battery goes dead.
  4. MajorLord

    MajorLord New Member

    I appreciate the replies, but what I had in mind was using a wheel with a motor, of the type usually used for a single wheel electric drive, not a hub generator ( Although thats an option, a Schwinn Trike is pretty heavy) A plain DC motor is also a generator, so this would allow the wheel to be used as a battery charger when the gas engine is running, and alternatively as a Drive motor to augment the engine when more power is needed, or in case of gasoline engine failure. Plan B is to find an old fashioned 12 Volt VW generator and run it from the engine's chain drive. This would actualy make the trike kind of a hybrid. Since where I live ( Napa, CA) is not a great place to ride a bike at night, I could probably get by with just charging up a battery from shore power to run the headlights, brake light, and ( Not required but I am going to do it anyway) turn signal lights, since all I would need to run during the day is the brake light. The rest is just to make it street legal. It appears that many new bicycle wheels with integrated hub motors are multiphase AC motors, which have no brushes and are more efficient and reliable. I am looking for the not-efficient, not reliable DC motor with brushes: I don't expect to wear it out quickly with the occasional, fair weather, daytime grocery store run!
  5. KCvale

    KCvale Motorized Bicycle Vendor

    You are asking a lot from a little 35cc engine.
    Pushing the trike, you, a battery, and generator that will literally feel like riding with a brake on.
    There is no free power.
  6. MajorLord

    MajorLord New Member

    Generator load on engine

    KC, while there may be times I actually want to use the wheel/motor as a brake ( You have to be pretty careful about braking a trike to avoid sudden death) The load on a generator ( How much current its load draws) sets how much rolling resistance the generator will have. Running a DC motor generator while just drawing a few hundred milliamperes to slow-charge the battery would add very little rolling resistance. It definitely would not run the full set of lights, horn, ham radios, or whatever else might go on the trike simultaneously. My Headlight and brake/tail lights are LED lights, and don't draw much power anyway. I really want to avoid using either a hub or "bottle" dynamo like most bicycles do for light. The Bottle dynamos are tough on tire sidewalls, and I am not sure that the hub-type generators can handle the mechanical stress of a beast as heavy as a Schwinn Meridian trike. With a Dynamo, I would have to isolate the unit from chassis ground, rectify the output, and then use a switching power supply to achieve 13.6 Volts for charging the battery at a very low charge rate. The flat terrain of my city and the low gearing of the Staton gear box should let me siphon a little energy without too much drag. Too bad the Honda engine does not have its own generator! ( Or electric start, which would be mega-cool!) I could make really ugly generator that connects to any rotating part of the bike and "shakes" a simple magnet/coil generator of the type used in Shake-powered flashlights, but I have not yet grown that desperate. The State of Kalifornia has not even sent my License plate yet.

  7. bigbikeseat

    bigbikeseat Member

    Here is something you can try. Turn on all of your lights and anything else you have on the bike and see how much current is drawn. That will give you the size of the battery you will need. If you are drawing 1 amp/hour, and are going to generate 200 ma/hour, you will have a shortfall of about 5 hours of charging (or riding time). You will have to know how long you will drive the bike during the day to make accurate assumptions on your charging system and battery size.. The problem with the DC motor as a generator is the high rpms it need to generate 12v, and it will be unstable because of the varying speed of a MB. If the charging system is inadequate, then the battery will have to be recharged when the bike is not in use. Which puts me back to my conclusion that a 15 amp lithium battery that weighs practically nothing is the only way to go for a 4 cycle motorized bicycle.
  8. KCvale

    KCvale Motorized Bicycle Vendor

    Until you put a regulator in.
    They will take everything the generator can give by the RPM and shunts what is over to ground.

    Heck, a 35cc Honda doesn't even make for a good generator all on it's own with no other drag.

    You have to really understand magnetism regardless of power generation.
    Magnets attract to metal, you can feel it with a magnet in your hand.
    That is drag, period.

    Try pulling energy from it and the drag goes up exponentially.

    HS made the 53cc HS 144F-D1 4-storke engine with a magneto to generate 12V 7A from the flywheel.


    Apparently the cost of generating power from even a 53cc engine that needs power to do it's job to provide power at gasoline prices was just silly and they quit making them.

    The only way to go for anything under 15hp in my book.
    You need power to create power, and it's not an efficient system with little power to start with.

    Your 115V wall plug can fill a LI battery for a couple pennies, filling a battery with a wimpy gas engine is not only more expensive gas mileage wise, it sucks that power from want you want to do in the first place, propel you!

    Just my advice, take it or leave it.
  9. MajorLord

    MajorLord New Member

    Well, no. A Linear regulator converts excess voltage to heat, but that would be tremendously inefficient. A switching regulator takes the DC from the generator, and uses it to run an oscillator, that boosts the voltage by using an inductor to create a series of voltage peaks, which are smoothed and set to a fixed value. These regulators ( Which cost about .99 from China) are about 98% efficient. The regulator itself draws a trivial amount of power when no current demands are made upon it. These have another advantage; Regardless of whether your input voltage ( The output of the generator) is higher or lower than the desired charging voltage of your battery's optimal charging voltage, the switching regulator will provide a constant Voltage output, which it does by virtue of using a pulse width modulator to vary the duty cycle of the ringing voltage boost circuit.

    If I had to use a very tiny little generator to charge my trike's battery and run the all lights simultaneously, I agree, that would place more of a load on the engine than is practical. However, as long as I am operating my trike in daylight, the only light I ever need to turn on is the brake light, which is an LED motorcycle tail light that draws about 50 mA. If I go hog-wild and run the turn signals ( Not actually required by law) I will draw the battery down, as would turning on the headlight. Since I don't plan on driving this thing at night, all the generator need do is to keep up a minor trickle charge on the SLA battery and keep ahead of the brake light demand. If I have to turn on the headlight ( There could be a total solar eclipse or something) my 7 Amp/Hr SLA battery provides a generous margin to provide power for the running lights ( Tail light, and headlight) All the lighting is LED except two incandescent panel lamps needed to draw enough current to make the turn signal flasher blink ( Yes, I could build a solid state flashing circuit, but I am lazy!) I will definitely keep an access point that allows charging the battery externally. As much as I love what a good Lithium battery can do, if I wanted to spend a zillion dollars on batteries, I could have built this as an all-electric trike. When you look at the potential energy of 1 Kilo of gasoline versus one kilo of Lithium battery, and compare the expense and weight, Gasoline is the hands down thermodynamic winner! Also, If I had built this as an electric, I would not have to jump through California's hoops to register the Gasoline powered bike as a moped, and I could stick a Walmart AA powered headlight/taillight on it ( With nearly 1.6 BHP of power; No civilian needs that much power!) Surprisingly, California processed my 20.00 check and sent me my license plate and registration card for a moped that strictly speaking, does not exist, or perhaps more accurately, it exists as a bunch of boxes in my garage. It took about two weeks. It is too cold and wet to ride, so I have plenty of time to build this right.

    I know that a few people have built the trike with an old-fashioned "bottle" type Dynamo, and a diode to prevent back voltage from trying to make the Dynamo act like a motor. The claim was that this was enough to keep the system charged, but my experiments with one of these dynamos ( Which generate AC) was that the output voltage was not high enough to reliably charge a SLA battery. Using a diode instead of a bridge rectifier also eliminates the negative going portion of the pseudo-sine wave generated by the Dynamo, and that's just a crime! Wasted energy.

    Now if I could find a brushed, DC motor wheel motor, I could use it as a brake/generator to slow the trike and charge the batteries, when coasting down hills, or from the frighteningly high maximum speed of the trike which I am estimating will be around 12 MPH, for regenerative breaking. This way, I would not be stealing engine energy at all ( Except indirectly assuming the engine takes me up the hill in the first place- (Thermodynamics are not just guidelines: They are the law!)

    What is really a shame is that I don't have an easy way to capture all that wasted energy that comes off the weed-eater motor in the form of heat! ( Hmmm, maybe if I run a turbo impeller on the exhaust to store energy in a flywheel......oh, never mind....)

    So all theory aside, I just need a reliable DC output anywhere between about 4 volts and 35 Volts that can supply about 500 mA

    Thanks for the ideas!
    Allen, BSEE, MSEE, PhD, FCC Technician License (GROL) with Radar
  10. bigbikeseat

    bigbikeseat Member

    The headlight has to be on while driving in the daytime or night time. AA electronics, Electro Magnetics Technician Senior, retired Lockheed Missiles and Space Co. Retired Semi truck driver. Ham radio operator. Electronic experimenter, circuit board designer. Metal fabricator.
  11. MajorLord

    MajorLord New Member

    Daytime headlights

    Good to know. Then I need my generator to keep up the headlight charge rate too. I know that motorcycles manufactured after 1978 require an always-on headlight, but I cannot find any citation that requires motorized bicycles ( Under 150 cc's) to operate with the headlights on except when required by conditions. ( i.e. darkness) I have CVC info that shows that the bike have the operable lighting, mirror, horn, etc., but I have only found laws requiring daylight running requirements on "real" motorcycles, not on registered Mopeds. Do you have a CVC or DOT citation on the requirement?


  12. bigbikeseat

    bigbikeseat Member

    I looked at a video where the officer wanted to cite the MB driver for not having his headlight on. You need everything going for you when you ride one of these things. My headlight is always on and no one has pulled out in front of me yet. So even if it is not a law, I ride with my headlight on . Today was my first 30 mile trip up to the dam. The little motor made the steep hill I didn't think it would make. The bike weighs 100lbs, and I weigh 250lbs. I was going about 5mph at full throttle up the steep hill. No issues. Got in a race with a road bike. Passed him with authority going uphill at 30mph. He got mad and when the hill turned downward, he caught up to me fast and passed on the inside. Good thing I was looking for him by turning my head.
  13. MajorLord

    MajorLord New Member

    Headlight legality

    I searched high and low ( no headlight pun intended) and could not find any requirement for a Moped to have a headlight on during the day. In fact, even on this page, in a conversation about California Law, another person had the same question come up. Nonetheless, its probably not a bad idea to have a headlight. I may run the low beam full time. Having had numerous cars turn left in front of me while riding regular motorcycles, I determined that motorcycles are like the Klingon cloak of invisibility! Mopeds, especially home-builts on the other hand, seem to attract cops like flies to honey! When I went through the Police Academy ( And dinosaurs roamed the earth) anyone with any class license could ride a moped, and the CVC was only about 500 pages long! Other than weighing stations and full-time motorcycle traffic cops, very few police actually know very much about the vehicle code. It's very complicated even for people with normal intelligence! Ask any cop to explain the right of way rules for a four-way intersection and see them collapse like slugs with salt poured on them! Every webpage I see about motorized bikes in all their various iterations shows that there is still massive amounts of confusion about the two basic classes, and endless bickering. I still have not figured out why a person with a class C driver license can drive a motorcycle with a sidecar or a trike, but a three-wheeled moped still needs an M1 or M2 endorsement. Go figure.

    Glad to see that you are a Ham too! Did you install a radio on your bike? I manufacture Amateur radios sold under the brand name "Micro-Trak" and distributed by Byonics, ( and a lot of our clients use our APRS trackers for Bicycle-mobile applications. That's kind of what got me interested in doing a Trike. Room for radios and groceries! I guess for now I will wait for my next generator to show up from E-bay. I would prefer to have a real drive on the generator, not a friction wheel on the tire, but if I end up with a bike I have to plug in to charge when I come home, it is not the end of the world.

  14. The_Aleman

    The_Aleman Active Member

    We MaB riders aren't required to have a daytime headlight. That is reserved for motorcycles (according to CA DMV: 150CC and up is motorcycle-class).

    Of course, having daytime light(s) helps considerably. I've run LED flashers in daytime for years, definitely helps make one more visible!
  15. KCvale

    KCvale Motorized Bicycle Vendor

    I won't even ride around the block without a daytime front strobe these days, won't let my help either, not even for test runs on repairs so I keep one ready by the door.

    Besides good brakes, a high intensity front strobe light will prevent the vast majority of potential painful wreaks, the motorists that just glance and see a bicycle just don't calculate your speed before crossing your path.

    A strobe makes everyone look just that extra second longer, and that's all it takes for most to wait another second or two.
    The ones that don't care are why you need good brakes ;-}