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IDEA DETAILSIDEA DETAILSIDEA DETAILS IDEA DETAILSIDEA DETAILSIDEA DETAILSIDEA DETAILSIDEA DETAILSIDEA DETAILSIDEA DETAILSMinistry Category: Hardware Problem Code: #MTY23Problem Statement: Retrofitting of existing vehicles for converting to Electric Vehicle (EV)College Code: 13227 Team Leader Name: Divyansh GoelPROPOSED SOLUTION FOR RETROFITTING OF CONVENTIONAL VEHICLESA major problem faced in retrofitting a conventional vehicle is that of modularity. The fact that one size does not fit all causes dilemma in mind of the designer while deciding specifications for the vehicle. A motor which is able to drive a hatchback will be unable to drive a SUV, a battery which is able to provide ample range for a light vehicle will be unable to suffice the need of heavy vehicle owners. Hence, we have created a solution which aims to solve the problem by targeting maximum number of vehicles currently running on Indian streets. If we take the number of hatchbacks and sedans running on Indian roads today we’ll find that they exceed the number of SUVs by a huge margin. According to passenger car sales were 2103000 as opposed to just 762000 sales in SUV category. Hence the major cause of polluting vehicles belongs to the hatchback and sedan category.Our Retrofit kit the ELECTRA20K aims in converting a passenger car into an EV with highest possible efficiency. However, our retrofit kit is capable of retrofitting SUVs as well but the durability and economic benefits of conventional SUVs as of now exceeds that of ESUV.The reasons are as follows:-1) Li-ion battery cost is decreasing but as of 2016-17 the cost is still high for long range vehicles, hence making a car conversion illogical.2) The durability of battery technology is yet to prove itself for off-road applications.Now we come to the question. Why does a passenger car conversion make sense?The reasons are as follows:-1) According to worker traveller survey 2011 by MINISTRY OF HOME AFFAIRS states maximum number of people in NCT Delhi travel to work daily for a distance of 22km to 40km. Hence a round trip of an average person does not exceed 40km. Therefore a vehicle with a range of about 100km is sufficient in providing for maximum number of people. This means ELECTRA20K has the potential for maximum adoption.2) According to Bloomberg’s survey an average traveller has the requirement of a range of about 100km.Hence by investing an equivalent amount (equivalent to buying a conventional car) owner gets less maintenance and running cost.WHY ELECTRA20K?The ELECTRA20K is a modular retrofit kit. This means it is capable of catering to a person with less range (travel distance) needs as well as a person who need high range. This is achieved by creating battery hotspots (potential places where a Li-ion battery pack can be housed), these hotspots are electrically connected during the retrofit and then if needed extension batteries can be placed in the hotspots in a plug and play fashion. The ELECTRA20K is also capable of driving the heaviest sedans and the lightest hatchbacks.This is done by selecting a motor which is capable of catering to both the categories.The hotspots are situated as follows:-1) The front boot of the car.2) The back boot of the car.3) The fuel tank of the car.The basic retrofit kit contains battery for the fuel tank of the car and the circuitry for the front and back boot. If the customer wishes to upgrade he/she can order another battery pack and place it in any of the two remaining hotspots in a plug and play fashion. This method reduces the base price of the kit yet making it capable to be sold for multiple range causing maximum adoption by average Indians.Technology stackOur technology stack is divided into two parts the hardware and software technology stack.The hardware stack consists of1) The motor2) Power Distribution Unit (containing the DC-DC converter and Controller)3) The Battery4) Transmission systemThe motor we have decided upon is the WARP-9 SERIES WOUND DC MOTOR. The reasons for why we have chosen a BDC motor instead of the popular AC or BLDC motor are as follows:-1) According to average range of ownership of vehicle is about 65 months or 5.4 years. An average life time of a BDC motor brush is around 15000 hours or 1.6 years straight. Assuming an average run time of 5 hours per day results in 8.3 years. Which is more than the average ownership period. Hence a BDC motor is able to cater for 8.3 years at a lesser cost than an AC counterpart (This is because AC motor needs extra components such as inverters causing increase in weight and cost).2) BDCmotor is easily available inIndiahence all the parts sourced fortheretrofit kit are available nowinIndia hence reducing the costof thekit and strengthening theMAKEIN INDIA initiative.3) TheBDC technology is easier toimplement and has been inapplication for long periods oftime.Some data of the WARP 9 motor is given hereThe WarP 9 ™ motor is similar to the ADC 9″ motor, but with numerous improvements. It is a 9.25″ diameter, series wound DC motor with a double ended shaft. Of the most notable changes, it has a larger com and utilize the large style brushes.? 1/2″-13 diameter terminal studs: Increased from 3/8″ diameter – bigger is better!? New brush composition: Handles higher voltages and currents – improves motor efficiency? New brush design: “split brush with pad” design handles higher voltages and currents – improves motor efficiency? Increased spring pressure: Spring pressure has been increased to allow improved commutation (note: This does NOT increase brush-commutator wear as might be suspected)! Higher spring pressures allow for increased commutation – which improves commutator wear over “bouncing brushes”.? Addition of optical RPM sensor hole: A 1/2″-20 hole is drilled and tapped into the DE for easy insertion and use of an RPM sensor.? Addition of temperature thermistor: This will allow the motor temperature to be be monitored.? Removal of brush wear indicators: To the best of our knowledge, no one ever used this feature. As armature voltage was used for signaling it was difficult to adapt and use.? Improved fan: Increased air flow will allow the motors to run cooler and more efficiently. The 15- blade fan is a new casting that will make using the RPM sensor easier as well.? Drive End mounting holes changed from “blind holes” to thru holes. If the wrong length bolts were used it could damage the DE head. Care must still be exercised to ensure that the mounting bolts do not hit the fan blades!? Temperature snap switch and thermistor plug will use the same black plug that was previously used for the brush wear indicators and accepts 1/4″, flat spade connectors, but it will now be counterbored. The com bars are more securely attached to the arbor, so they will be less likely to lift. The drive shaft is bored for a pilot bearing and drilled & tapped for a 5/16 – 18 bolt. The tail shaft also has a 1/4 – 20 bolt hole to mount tach sensors or secure couplers and accessories. Again, duplicated the ADC 9″ mounting bolt pattern allowing clients to use preexisting mounting adapters. Class “H” insulation is used throughout the motor. The drive shaft and tail shaft have standard keyways cut into them. Extra large brushes are designed for the high voltages and currents used by today’s electric vehicles. Our motors use specially formulated, high performance brushes manufactured exclusively for our motors by Helwig Carbon. The split brush design offers longer brush life and better commutation. Four wires go into each high performance brush (two per wafer) versus the more common single wire per brush. Most manufacturers use 3/8″ terminal studs. Our WarP 9 motors use 1/2″ terminal studs. WarP Motors use only low-loss laminations and welded or fused commutator connections for peak motor performance. This superior methodology lowers heat build-up and yields longer operating time per battery charge. Both the armature and the field assembly are resin varnish treated to lock in mechanical integrity and to provide permanent environmental protection. Our laminations are keyed on to the armature shaft.QuasaR Power Distribution Unit• Over 300 amp charging from a suitable source (i.e. a DC source of higher voltage than the battery pack – “buck mode” or a up to 80 amp AC input to an internal rectifier).• Battery pack input/output (source to controller/target for charging), controller supply connections, and charging source input connections. All connections occur within the enclosure to maintain an OEM-quality design that keeps high voltage connections from being touched under the hood.• Automotive quality external low current connections.• Internal DC-DC converter with up to 50 amp capability. Includes anti-bricking functionality to prevent the battery pack from being drained over long periods of time (e.g. long term storage). Provision exists to “jump start” the 12 volt system in case of an excessively drained pack. Converter is always active unless the input voltage falls below the configurable “low input voltage cutout” value. The DC-DC output voltage can be be configured with a trim pot from 10 to 15 volts.• Liquid cooling for thermal management.• CANbus for communications. OBDII capability for integration with utilities such as “Torque” for monitoring and configuration. Custom “apps” can be designed with relative simplicity to take advantage of all information provided by this device and others connected to the CANbus. Configuration of all adjustable parameters occur through the CANbus interface using a combination of custom OBDII commands and direct CAN messages.• A mode of operation is available (and strongly suggested to use) that requires communication from a BMS which is monitoring parameters such as individual cell voltages and temperatures. The QuasaR™ will be able to stop charging if the BMS indicates a stop condition or if the BMS has not responded within a certain time frame.• An optional “stop” input (emergency cutoff input) is be provided to interface with a less sophisticated BMS (this mode of operation is not recommended).• Input operating range from 24 volts to 500 (all hardware rated to 600 volts).• Battery pack maximum is 370 volts• Configurable parameters:? Input voltage limit? Constant current and constant voltage limits? Charge termination event (CV, CV w/ programmable cutoff/termination current, BMS event CAN message or external 12V input, CV w/ timer)? CV termination current? CV current limit? CC current limit? CV timer value? Input current limit? Pack capacity? Low input voltage cutout for DC-DC• Charging current control within +/- 1 amp.• Voltage control within +/- 1 volt.• Charging indicator output line that is active during charging.• Cooling output line to control a liquid cooling pump intelligently.• Motor blower output line to control the motor blower. When used in conjunction with the optional motor temperature monitoring CANbus module, the QuasaR™ can adjust the blower speed to keep the motor temperature at a minimum.• Charging current monitored up to 300 amps.• 4 external LEDs to indicate status• Sealed enclosureTHE BATTERYWe have chosen to use the PANASONIC UR18650ZTA battery which is a Li-ion battery with the following specifications:-Nominal Voltage (V)3.7Typical Capacity (mAh)3000Charge Voltage (V)4.35Diameter (mm)18.6Max Height (mm)65.3Approx. Weight (g)49This spec allows for a range of 126.4 Km for a 900Kg vehicle.The calculations are as follows:-Weight of the vehicle = 900 kg or 2000 lbsAverage Watt per mile = 2000/10 = 200W/mile or 125 W/kmBattery pack size possible for a 35 ltr fuel tank car = 19.7 KWh(we have taken the volume as 35 ltr as it is the minimum fuel tank capacity of a hatchback, the only car which had less volume was the first generation tata nano with 15 ltr tank)Volume of 1 cell = 17.74 cm^3Number of cells possible in a space of 35ltr = 1972Assuming 10% decrease in space we get nearly 1780 cellsNet battery pack capacity = 1780x3000x3.7 = 19.7 KWhSince the pack cannot be discharged below 20% the net capacity = 15.8 KWhRange = Net capacity/Wh per km = 15800/200 = 126.4 KmTRANSMISSION SYSTEMThe transmission assembly of the car will not be removed and will be used in torque transmission from the motor to the wheel.? The transmission of the car includes gearbox and clutch assembly.? The clutch assembly will be connected to the motor using an adaptor plate and spline coupler.? Bushings will be provided to support the adaptor plate attached to the clutch assembly.? The gearbox of the car can be used for gear shifting just like a normal car but because the motor provides instant torque, the driver should start with the second gear which would help in controllability of the car.COG BALANCING? There will be best efforts to keep the centre of gravity of the vehicle undisturbed by balancing the weight of the motor and control unit with the batteries.? The motor and control unit will be placed altogether which will be balanced with the weight of the battery.BATTERY PLACEMENTIn electric vehicle, safety and reliability of battery packs present the highest challenges to a large scale.? Strategic battery placement technique should be used in accordance with the design of the vehicle.? The fuel tank and any other components of the car which is related to engine will be removed.? The space occupied by the fuel tank will be replaced by battery packs.? The space below the front seats can also be used for the placement of battery packs.? As we have the option of increasing the battery packs in order to increase the range, the owner has to compromise with the boot space in order to increase the range as the boot space will be used for the placement of battery packs.BATTERY COOLING SYSTEMThe preinstalled radiator of the car can be used for battery cooling system.? For battery cooling system, there are two methods-1. Surface cooling2. Tab cooling? After some research we have found out that surface cooling method is less efficient as it results in degradation of battery life due to uneven cooling whereas the tab cooling method causes even cooling and is thrice efficient than the former method which results in longer battery life.? An accessory plate and belt driven mechanism will be required to pump the coolant in the battery cooling system.Software StackThe software stack contains the following softwares :-1) AutoCAD2) EAGLE3) MICROSOFT OFFICE4) AUTODESK INVENTORUSE CASEThe retrofit kits can be used to bring new life to conventional vehicle. With decreasing battery cost and economics of scale the retrofit kits will become cheaper overtime. It’s best suited for vehicles which are no more capable for catering to the owner’s requirements. Hence by investing the money in retrofitting will make more sense as The TOTAL COST OF OWNERSHIP comes down drastically. Due to our modular approach our retrofit kit is capable of mass adiption.


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