56 which has allowed Electrogenics to modify it to support fixtures for the two isolation mounts supporting the drive motor, which sits in the transmission tunnel. Motor, voltage and battery decisions There are two options for the motor itself, one sourced from the UK and the other from China – both radial flux units to fit the narrow space of the transmission tunnel. “One of the nice things about having made all the effort to develop our own VCU software is that it means we can use any motor we like. Manufacturers typically don’t supply their motors with software and often don’t supply the inverter either, so if you don’t write your own software, your options are very limited.” Drummond says the powertrain design process begins with how you want the vehicle to perform, which drives motor choice. “Motors come in certain operating voltages, and so that the motor you choose determines the operating voltage, you build a battery to deliver that operating voltage.” While Electrogenic builds EV powertrains that run on voltages from 48 V upwards, most of its off-the-shelf kits run at nominal voltages of 350390 V, and the sports version of the E-type kit has a maximum of 450 V. “The envelope for batteries is determined by the physical space in the car, and the extent to which you want to load up the suspension,” Drummond says. “That determines the upper bound on the battery volume. Then, you have discrete steps as you trade-off between motor voltage and how you combine battery modules to come up with approximately the volume and kilowatt hours you’re looking for. “That gets you to your high-level spec of motor power, torque and rpm, as interpreted by your transmission to give you the final rpm and torque ranges at the wheels. Then, that influences your choice of battery specification, and you go around the loop until you get a combination you’re happy with.” For the E-type conversion, a nickel manganese cobalt oxide (NMC) chemistry was chosen by Electrogenic for both battery pack options; one with a rated capacity of 40 kWh and the other at 60 kWh, which provide ranges of 140-150 miles and 200 miles, respectively. These are made up of VDA modules of about 6.8 kWh each, which are of a standard size and shape, and secured by the cassette system. Thermal management & safety The thermal management system includes cooling plates that slot between the modules with an interface consisting of thermally conductive paste. “To get good thermal conductivity, you need to make sure you don’t have any air in there insulating things,” says Drummond. A pumped supply of water ethylene glycol coolant runs through the cooling plates, moving in and out of the enclosure through connections to a bespoke radiator. Electrogenic does not use the original radiators, partly because they tend to be old, and partly because the vehicle needs two separate cooling loops and associated heat exchangers – one for the battery and the other for the motor and power electronics, such as the inverter and onboard charger – while also leaving room for an air-conditioning condenser. “Obviously, the radiators don’t need to be as big as they do for an internal combustion engine of equivalent power, May/June 2024 | E-Mobility Engineering The connection for the onboard charger is under the original fuel-tank flap, while the fuel tank itself has been replaced by the rear battery box for weight distribution The 12 V battery in this car is a LiFePo unit from Ultramax. It operates the main HV contactors, powers the lights in emergencies and is charged by the DC-DC converter
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