Nikola Novaković – Project leader of the team Electric Arrow.
“The Tractive system accumulator gives 600 VDC on its output. It has a capacity of 7.7 kWh and it consists from 5 smaller segments.
In total it has 700 Li-ion cells in a 140s5p configuration.
Every segment has two BMS Slave (Battery Management System) boards which monitor the state of the cells. They measure voltage and temperature of the cells.
All 10 of these PCBs send data via a serial communications line which ends to a Master BMS.
This board is practically a microcontroller which is the brain of the accumulator. It has an integrated MCU chip (like the ones on our telemetry units).
The Low Voltage accumulator gives a 12 and 24 VDC voltage on its output. Designed in the same way as the HV Accumulator, the accumulator is built using Li-ion cells in a 4s8p configuration.
It also has its own Low Voltage BMS board.
Because the Inverters of the Tractive System demand a 24 V supply the accumulator has a 12/24 VDC converter using a boost converter.
All actions regarding the handling of the Tractive System, such as current and voltage measurements, safety circuit, pre-charge, discharge, visual and sound signalization of the TS state are done on a special board which we named TSMD (Tractive System Management Device).
Creating this board will be a real accomplishment because it has to sustains 600 Volts and currents up to 100 A.
To make matter even more difficult, the board features both HV and LV systems which are galvanically separated.
We are still planning on how to implement our ECU (Electronic Control Unit) which will command the whole vehicle.
So far it is most likely that we will use a powerful MCU with Simulink programming capabilities which will be plugged in our shield board.
The telemetry will be the same as that in our combustion vehicle which was proven to be very reliable in terms of durability, flow rate and accuracy last year.
The same goes for our LCD Display, with minor software changes regarding what information will be displayed.
As we consider the lithium battery pack the most critical part of an electric vehicle, we set our main goal for this season to design and properly test high voltage battery pack.
We want to manufacture and test our custom made Battery Management System for both our high voltage battery pack and low voltage battery.”
For the 2018/2019 season, it is planned to present the conceptual design of the vehicle, which will have significant improvements in relation to the 2016 version.
System design and development is currently underway, and component testing will follow shortly thereafter.
Going to a large European competition to compete in Class II will be an introduction to the design and testing phase, for the 2020 season.
As one step closer to that, the team of Electric Arrow has already qualified for the prestigious competition held in the United Kingdom on the famous Silverstone track.