The goal here is to make a 100% solar-powered vehicle, free of the tether of a charger. This necessitates a large panel. I considered a KC65 and a KC125 and finally chose the latter.
The trike is a used 24" model I saw at Sun West Cyclery 625 A19 N, Palm Harbor, FL 34683 tel 727 785 0110. After looking at some 'bents EZ-1 and EZ-3 I decided for now that most of the R&D funds will go into tech stuff rather than frame. The 24" wheels make motor exchanges possible with the original bike. This time, I bought the WE BD24-10 system, which uses the same motor as the BD36 for half the price. The charger and controller will not be used on this one but will be studied.
Picture of the unmodified trike with Wifey demonstrating proper usage.
It was rather dorky looking but very comfortable and easy to pedal with it's one-speed sprocket.
I added a support frame in the back for the panel. I made it frome chain link fence parts and some TV antenna poles.
Plans include a WE BD36 front wheel motor, a KC125 solar panel and various controls. Check back here as I update this page.
The motorized wheel and tire are ready to be mounted.
I had to file the fork slots sightly to admit the keyed shaft. The motor casing has radial ridges that rubbed against the fork tines until I added a washer on each side to separate tines another 5 mm (total). The casing had the word AOTEMA and 3 Kanji characters in relief.
Unlike the BL36, the BD36 is a brushed DC motor, plain and simple. It will run on as little as 12 volts and haul ass at 36. A friend ran one on 60 volts and got about 2 horsepower but he also burned it up. Two hp is about in proportion to a small motor scooter by weight.
Another view and front bracing added.
Trying the moter at variable voltages.
I tried to run on just the panel. The panel has internal resistance of about 3 ohms since a dead short can produce 7 amps and open circuit voltage is 21. The motor was seeing about 2 volts.
A 12 volt battery can stabilize things, run the motor and get recharged directly. A fresh 7 amphour SLA had an open circuit voltage of 12.8 on a comfortable day (about 75 deg F but not measured). I used common household switches and plugs because they're cheap and can handle the current. The motor has a switch and is simply "plugged in" to the battery (receptacle). The panel is also plugged in (parallel). This will serve as a first test but the panel can easily overcharge the battery.
Quick and dirty wiring. Not to "code".
As expected, the 12-volt system was quite sluggish. On level ground in bright sun, the trike DID MOVE UNDER ITS OWN POWER! It was about walking speed. When stopped, the panel socked it to the battery, pushing its voltage up to about 15 or 16. I added a shunt regulator. I dislike these because they "waste" power by shorting the panel. An AM radio confirmed a lot of pulsed shorting was going on. A steady buzz could be heard whenever the panel put out more than the battery could safely handle.
Next plan is to try a higher voltage. I have dabbled with voltage converters and successfully run 18-volt laptops in a car, BUT this time it needs to be 99.99% efficient. WE uses PWM controllers which are pretty cool, but some energy is always wasted. The motor coils WILL react and the AM radio confirms a lot of "broadcast" energy from these things. I added another 12-volt battery, using hose clamps as before. I like building things out of reusable parts! I made a "hi-lo" switch that will place this 2nd battery in series or in parallel with the first battery for a 12/24-volt system. I needed a triple pole double throw of sufficient ampacity. Fortunately these are commonly used in 3-phase electrical systems and I had a few on hand.
This ran about jogging speed, faster on well-lit level surfaces. I didn't have to pedal. People were starting to notice what I was doing and I got a lot of "thumbs up" and compliments. Next, I will add two six volt SLA's of similar ampacity to create two 18-volt banks. The panel can charge an 18-volt battery more efficiently than a 12-volt one. Maximum Power Point Charts suggest 17.5 volts.
I removed the shunt regulator as well. I expect to h/a at 36 volts. It will be too fast (for a trike).
I discovered that the panel can consume about .5 amps and run the battery down when it is not illuminated and still connected to the 36-volt battery arrangement. Rather than suffer diode losses, I added a simple switch to cut it out of the circuit when it cannot help (in 36-volt mode or darkness) and used a 2-amp charger to restore the batteries from deep discharge to full again in about 5 hours.
I made a 10-mile round trip averaging 12 mph on level ground with stops for a 70-minute period. I only started the bike from dead stops with the pedals and assisted one climb of about 300 feet. There was full overhead sun and only 5-10% of the pathway was shaded. The trip ended with good power and the battery accepted 2 amps from the charger for 2 hours. That same trip on my other e-bike (w/o solar) requires 3 hours of charging at each end of the 5-mile trip. 04/19/06 discovered wiring problem that left 2nd bank out of parallel connection. Therefore 36-volt operation discharged all batteries but 18-volt operation used and charged the 1st bank only. This explains the need for additional charging (to simply replenish the 2nd bank).
At school 5 miles away and no plug in recharge.
I am still awaiting 2 special-ordered rear tires. The two dry rotted tires I have now were practically flat, adding a lot to the rolling resistance. I expect much better results when these arrive.
With new tires and wiring problem resolved (above), I expect no net loss of charge on a trip that has full sun. In other words, I should not need to charge the battery during any downtime in the sun or from an AC charger. This needs a better match between the panel and the 18-volt bank. The MPP chart above shows a maximum around 17.5 volts but, at that voltage, I am seeing only a fraction of an ampere flowing into the battery. I need to boost the panel voltage slightly to get a better flow, at least 1.5 - 2.5 amperes. The bistable multivibrator circuit shown is exciting a toroid at its resonant frequency of about 21 khz and boosting the panel voltage to about 33 volts.
Also, a radio plus a better speaker were mounted behind the seat. It is currently independent of the solar/motor circuit. If I wind up with "excess" power, this may change.
New circuit added to better match panel to 18-volt system.
05/02/06 - I have gotten many of the technical problems solved only to be shut down by legal ones in Pinellas County, Florida. My solar-powered trike is technically a motor vehicle but in reality it doesn't go much faster than someone could pedal it. So I cannot use pedestrian/bicycle lanes and paths. It also is no match for normal road traffic and can't be used on the public roads. They have left me with no place to pursue this technology! As of the last test run I had a top speed (est) of 20 mph, partial regenerative braking, and the ability to end the excursion with a full battery charge.
Control panel with regenerative braking.
The three switches are (from left to right) SPST battery off/on, SPDT motor on/shorted, and SPDT PWM throttle/bypass (fast).
There is enough for a power booster for the speaker (upper right).
05/11/06 - I have obtained a special (medical) permit to get back on the trail.
The electrical system was changed back to a 12/24* and will eventually be 6/12/24. Regenerative braking is acconplished by "downshifting" thru the lower voltages. The motor acts as a generator at the higher speeds and dumps the excess energy back into the battery bank. Finally a dead short saves wear and tear on the lone caliper on the front wheel. I have been fearful that that single mechanism might fail on a steep incline.
*The maximum power point strategy at 18 volts made too much reliance on the step-up toroid which had some inefficiencies of its own, manifested by heat, erratic charging and diode failure.
05/30/06 - Attempted to ride under solar power to Passagrille Beach, about 25 miles away. 10:10 AM left home in Ozona. I took the trail to Schiller, then A19 to downtown Clearwater under full power. Crossed Causway bridge partly without power. I pedaled hard for 75% of the climb with the motor helping and walked the last 25% uphill without the motor at all. Clearwater Beach proper was not bike/trike friendly at all. There was a lot of construction and few sidewalks. At Shepards, I verified that I could park and recharge an electric bike. I crossed the bridge to Sand Key, again with my help getting up the incline. It was now about 12 noon. From Sand Key to Indian Rocks Beach, the sidewalk allowed moderate speeds (10-15 mph) with special care regarding the driveway bevels that can tip the trike precariously. Indian Shores had no usable sidewalk and the road was busy. I rode on a sandy shoulder for about 2 miles. From Redington Shores to Redington Beach, the road was wide and clear enough to do about 20 mph. At that speed, I am using about 15 amperes at 24 volts to give about 360 watts (or 1/2 horsepower). This is glorious cruising, getting lots of thumbs-up and cheers but also draining the battery. The panel, under the best conditions can only supply about 125 watts. As it was, there was considerable cloudiness that I did not anticipate at the start. I began to lose serious power and worse, almost lost control of the trike on uneven pavement. I saved the bike but stubbed my toe badly. I had come about 3/4 of the way under full power for all but the two bridges. It was 1:30 pm and it seemed prudent to head back. I washed my toe in the ocean and continued on to Madiera Beach in order to crossover to the mainland. I really wanted to get back to the safety of the Trail. Crossing the Stuart Causeway at 150th St. got me to a bike-hostile intersection of Tyrone Blvd and A19. I pedal-assisted the motor from this point on. I went north on A19 and rejoined the Trail at mile marker 10 at 2:30 pm. I went 17 miles to get home (near mile marker 27) at 5:30 pm having taken a few rest stops along the way. I also got an opportunity to try a out Segway.
These are state-of-the-art solar cars that go about 45 mph avg. My trike goes about 12 on pure solar (zero net battery discharge).
01/11/2008
