PROJECT E-MOPED

In this project a Honda Activa with a conventional IC engine was converted into an electric-driven Moped by using a hub motor, controller, swappable battery system and on-board fast charger. It involved various mechanical fabrication processes such as material selection, welding, cutting, grinding, riveting and electrical work such as battery pack assembly, Motor controller wiring and final assembly.

The various processes carried out in converting an Activa into an Electric moped are divided into two sections:

  • Electric Moped Mechanical Workflow
  • Electric Moped Electrical Workflow

ELECTRIC MOPED MECHANICAL WORKFLOW

DISMANTLING OF VEHICLE

The vehicle is dismantled by removing the parts so that the chassis of the vehicle is exposed. The rusted parts are sprayed with WD 40 for easy removal. The parts such as bolt, nut, and screws are kept aside which will be required in reassembling the vehicle.

Dismantled Vehicle

SWINGARM WORK

The existing swing arm of Activa cannot be used as it is mounted with the engine. The calculation regarding hub motor size required wheelbase and height of the vehicle are made. And swing arm of Yamaha FZ Bike was closely matching the requirement. The slotting on the two sides of the swing arm is made to mount the hub motor shaft. The additional tube is arc welded to the Activa frame at the bottom so that the swing arm is bolted to the mainframe.

Slotting of Swingarm and tube welding

SUSPENSION WORK

Usually, Activa comes with single suspension but in our project considering the hub motor size and swing arm profile we used customized two suspensions springs on either side of the frame. The length of the springs is adjusted as per the required vehicle height by welding the extra attachment rings at the end. The extra brackets for mounting the suspensions are fabricated and welded at specific positions on the vehicle chassis and swingarm.

Suspension Mounting

BATTERY AND CHARGER BRACKET WORK

The storage compartment under the seat which is generally used to store the helmet is employed for the placement of the battery pack. The placement of battery and power supply was a challenging task as it was meant to be swappable making it easy for the user. At first, a proper casing is made for the battery pack by using 3mm ABS sheets, which are cut as per design using a laser machine. Then the brackets are made by using a 20X20 mm mild steel angle by cutting at specific lengths. The angles are welded to the vehicle frame at the desired positions.

Angle bracket fabrication

To protect the battery and power supply from water splashes it is covered in all the sides by using 1mm mild steel sheets. The sheets are riveted to the angle by drilling a hole and by using a hand rivet tool. Further gaps are filled by using clear silicone on all the sides to ensure that water doesn’t seep inside the compartment. Belts are provided to the battery and power supply so that they are strapped intact without any vibrations or movements.

ABS Battery Pack Casing
Sheet Metal Work

The final assembly of the battery pack inside the compartment with the necessary wiring and other peripherals such as handle grips is as shown below

Battery Pack Compartment

BODYWORK

The bodywork is done to adjust the battery position without altering vehicle dynamics. The rework on the side stand is made for the required height of the vehicle. Seat lock position is altered and required adjustments are made. Further MSB mounting, throttle, and extra switches are mounted on the vehicle body.

Seat Lock

REAR BRAKE

The rear brake is upgraded from wire to hydraulic disc brake. The brake lever is mounted on the handlebar. The brake caliper is attached to the disc of the hub motor by using a bracket and Allen screws.

Rear Disc Brake

ELECTRIC MOPED ELECTRICAL WORKFLOW

 BATTERY PACK

The battery packs used are enclosed with ABS plastic enclosure and the two batteries are interconnected using Anderson power pole connectors, each battery pack constitutes 180 cells in a 13S 10P configuration.

Battery Pack

Battery cells and configuration:

Cell 18650 Li-ion (NMC)
Nominal Voltage 3.7 V
Rated capacity 2500 mAh
Constant discharge current 5 A
Cell assembly 13S 10P (X2)
Number of cells 260
Battery pack voltage 48 V (nominal) 55 V (peak)

HUB MOTOR

The Hub motor is mounted at the rear end of the vehicle. The motor is equipped with two sets of Hall sensor wires in case one of them gets damaged facilitating ease of replacement. The Hall sensor wires along with the three Phase wires are extended and passed through PVC conduit along the chassis frame till the front end of the vehicle.

Hub motor

Specifications of Hub motor:

Size 12” (304.8mm)
Motor rating 2 KW
Peak power 4.5 KW
Speed 1200 rpm
Top speed of the vehicle 70 kmph at 200 kg gross weight

CHARGER

The charger has a modular set up such that it could be either placed inside the vehicle to facilitate onboard fast charging or it can be removed and taken along with the battery pack to provide fast charging facility through domestic power supply. The fuel tank of the vehicle is removed to place the charger. Mild steel angles and Aluminium sheets are used to make the charger compartment.

Charger Compartment

Specifications of Fast charger:

Charging voltage 55 V
Charging current 15 A
Charging duration ~ 3.5 hrs. (0 – 100%) ~ 2 hr. (20 – 80%)

MOTOR CONTROLLER

The motor controller is placed at the front end of the vehicle, facilitating in better ventilation and thus heat dissipation. This also allows easy access of the controller for wiring and maintenance purposes.

Motor controller

Motor controller rating:

Operating voltage 35 – 60 V
Rated current 80 A
Features 3 Speed modes , Reverse mode, High brake, EBS

MISCELLANEOUS

Wiring:

Appropriate wire gauge was selected after evaluating the magnitude of current flowing through each connection. Hence, higher gauge wire was selected considering the safety factor.

The wire gauges are as follows:

Power wires 6 SWG
Phase wires 11 SWG
Miscellaneous 18 SWG

Ignition:

The ignition wire is connected in series with the vehicle key, SPST switch and a 5A fuse. The other end of this connection is connected to the positive terminal of the controller. The key ensures that the vehicle is turned ON by authorised persons only while the Fuse is used for safety purpose ensuring smooth operation even under repeated switching action.

Speed modes:

There are three speed mode options viz., LOW, MEDIUM & HIGH. These modes are accessed by a SPTT switch mounted on the vehicle dashboard.

Reverse mode:

The reverse mode, in which the motor runs at a lower speed but in the reverse direction can be accessed by a SPST switch mounted on the vehicle dashboard.

In the end, all the required parts have resembled and the vehicle is tested for its performance

Battery and Charger Compartment
Final Vehicle Assembly
Final Vehicle Assembly