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