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.
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.
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.
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.
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.
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
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.
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.
ELECTRIC MOPED ELECTRICAL WORKFLOW
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 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)|
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.
Specifications of Hub motor:
|Motor rating||2 KW|
|Peak power||4.5 KW|
|Top speed of the vehicle||70 kmph at 200 kg gross weight|
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.
Specifications of Fast charger:
|Charging voltage||55 V|
|Charging current||15 A|
|Charging duration||~ 3.5 hrs. (0 – 100%) ~ 2 hr. (20 – 80%)|
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 rating:
|Operating voltage||35 – 60 V|
|Rated current||80 A|
|Features||3 Speed modes , Reverse mode, High brake, EBS|
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|
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.
There are three speed mode options viz., LOW, MEDIUM & HIGH. These modes are accessed by a SPTT switch mounted on the vehicle dashboard.
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