ower converters can be of different variations, for example, DC/DC, AC/DC or DC/AC depending on application or preference. When choosing a power converter several factors must be considered such as its input voltage with the benefits of a higher voltage outlined in paragraph 1 page 3, its ability to drive the chosen motor as this limitation determines the current and voltage ratings of the motor [7], cooling system as the converter is prone to getting hot during operation, longevity if used in conventional purposes but not so much of an issue on a racing bike, weight and volume of the converter are also critical in the overall bike design. The chosen power converter for this design is the DC/DC converter Hybrid pack ™ 2 from Infineon [12].

The device is robust and programmable which makes it versatile when being implemented in different applications. It is designed to be used as a Motor and/or generator inverter for Hybrid- and Electric Vehicles and Range Extenders providing 100kW of continuous power. Accommodates a 3-phase Six-Pack configuration of Trench-Field-Stop IGBT3 and matching emitter-controlled diodes as well as designed for a 150°C junction operation temperature. The chips are rated at a maximum of 800A/650V and includes a Pin-Fin baseplate for direct liquid cooling which significantly improves the thermal cycles capability extending the lifetime of the power module and enabling a very high-power density [12]. It is a popular choice amongst electric and hybrid vehicle manufacturers. Figure 3 below shows the layout of the module including its component parts [12] showing the electrical energy transformation from dc to ac interfaced with high-speed motor, coupled to the rear wheel.

Figure 3: Application Block Diagram of HybridPACK™ 2 [12]

b. Electrical Power System

The electrical power system comprises of the battery management system (BMS) which is an electronic control system for the lithium battery cells and the battery pack which is a key enabling system component in electric motorcycles as shown in figure 1 (page 2). Low-cost lithium batteries cells with higher power densities and improved power factors have changed the way power is used and stored onboard an electric motorbike making them suited for mobile applications [8]. When choosing lithium battery cells, the amount of energy storage required, the rating of the motor and power densities needs to be considered. An appropriate number of series and parallel lithium battery cells matching the motor rating with respect to the maximum voltage allowed by the relevant electric motorbike racing competitions are chosen. For example, MotoE regulations have battery voltage limitations of +/- 300V.

Lithium battery cells have a very non-linear charge/discharge curve making them relatively difficult to manage [8]. For a lead acid battery, measuring its voltage is the easiest way to tell how charged it is and from that data, the state of charge can be worked out. With a lithium-ion battery, it is slightly difficult to work out making it very hard to tell the state of charge of a cell as the voltage relative to the state of charge is very flat around 60% of the charge/discharge curve with sharp inflections at both ends [8]. This makes it relatively easy to cause perm