Circuit Diagram for the Dahon Electric BModification underway in the basementOriginal Dahon Folding Bike
OwnerThomas and Drew Flechsig
LocationBurtonsville, Maryland United States map
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VehicleDahon Electric Bike
A light-weight, single-speed Dahon folding bike has been modified with 36 volt, 12 amp-hour battery power and a 1000 watt DC electric motor. The vehicle includes a key switch for secure access, a handlebar-mounted start button and an emergency kill switch for safety.
MotorMY 1020 Permanent Magnet DC
1000 Watt, 36 Volt, 35 Amp, >3000 rpm
11 lbs, 4" diameter X 6" length
DrivetrainModified the drive train (12/26/06) to increase top speed to 32 mph
Uses 8 mm chain
Motor Sprocket: 10-tooth
Wheel Sprocket: 44-tooth

Original Configuration (before 12/26/06)
Uses #25 chain
Motor Sprocket: 11-tooth
Wheel Sprocket: 65-tooth
Controller CT5319
Controller 24/36 Volt, 100 Amp continuous, 150 Amp Peak, 1.5 lbs, approx 4" X 4" X 2", Uses Hall Effect Wrist Throttle.
Batteries3 UB12120, 12.00 Volt,
3 Sealed Lead-Acid Batteries. 12 Volts/ 12AH each. Dimensions: 3 3/4" x 3 3/4" x 5 3/4", 9.5 lbs/battery
System Voltage36 Volts
Charger JC-36
36 Volt, 1.6 Amp battery charger with multi-colored LED. Charger uses 3-prong in-line plug that connects to the battery tray so charging can be performed without removing the batteries
Top Speed32 MPH (51 KPH)
(Calculated speed based on 3000 rpm motor, 10:44 gear ratio and 16 inch wheels) Qualitatively, it's very fast.

Completed the latest gear modifications on 12/26/06.
AccelerationQuick out of the blocks! Lots of fun to ride. I can even accelerate nicely up a hill near my home which has a 20 degree grade and is about 75 yards long!
RangeRange will depend upon driving conditions. 12 AH battery capacity allows a run time of nearly an hour.
Seating CapacitySingle Rider
Curb Weight77 Pounds (35 Kilograms)
Bike Frame/Wheels = 25 lbs
Batteries = 29 lbs (3 @ 9.5 lbs/battery)
Motor = 11 lbs
Controller & Contactor ~ 3 lbs
Aluminum & Steel Brackets ~ 9 lbs
Tires16 inch tires (40 PSI)
Conversion Time3 Months Total - includes concept, design, and fabrication
Conversion CostTotal cost ~ $460
Consisting of the following:
Used Dahon Bike - $100
MY1020 Motor - $75
Controller and Throttle - $80
3 Lead-Acid Batteries - $50 (+ $25 ship)
White-Rogers Contactor - $18
Miscellaneous Sprockets, Chains, Switches, Wiring and Materials - $112
Additional FeaturesVehicle includes a key switch for secure access, a handlebar-mounted start button (with latching relay) and an emergency kill switch with lanyard for safety. Power circuit incorporates a White-Rogers/RBM Contactor so that the battery is connected to the motor only when the key switch, kill switch and start switch are all "ON". See the circuit diagram to the right for details.

Vehicle also includes panel-mounted fuses for both the motor and control paths. Fuses are mounted on the battery tray for ease of access.

White-Rogers Contactor, 36 Volt, 100 Amp,Type 124-117111

Two 30 Amp Slow-Blow fuses configured in parallel in motor circuit path.
2 Amp Slow-Blow fuse in control circuit path
Improvements/Lessons Learned: With the added weight of the batteries and motor drive, the bumps on a rough road are more apparent. To improve the comfort of the ride, I will make sure that the base vehicle for my next project includes shock absorbers.

Other possible improvements include adding a voltage, current or amp-hour indicator. Also, researching Continuously Variable Transmission (CVT) used on pocket bikes to improve low-end torque and top speed. Investigating potential use of Li-Ion or NiMH batteries, if I can find an affordable source.

code by jerry