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Establish and challenge requirements: A top-down design approach is taken, starting with system goals and distilling those down to functional and engineering requirements. Requirements are constantly challenged to ensure they accurately reflect the goals of the system. Bias is taken towards having the lowest possible number of requirements to ensure a lean system. If a requirement is missed it can be added at a later stage. Conversely, it is very unlikely that an unnecessary requirement will be identified at a later stage and removed.
Delete parts: All parts of the system are analyzed and their existence justified. Components not required to fulfill the predetermined requirements should be removed from the system. Before attempting to solve a problem, it should be determined whether the problem needs to be solved in the first place.
Simplify and optimize: The remaining parts are simplified and optimized for the requirement they are intended to fulfill. Simplicity improves efficiency, reduces the chances of failure, and shortens the development cycle which ensures a higher chance of success. However, optimization should not be performed on parts that shouldn't exist, hence it is the last stage in the design process.
High Voltage
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Main Power Switch
The main power switch consists of 3 EV200 series relays. One relay is located at each terminal of the main battery and at the positive terminal of the solar input. This allows the battery, motor, and solar array can be disconnected from each other and all HV conductors exiting the battery box to be disconnected from the battery as required by ASC 8.6.A.4. The main power switch is located inside the battery enclosure and controlled by BMS system from the carrier board.
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Panels are connected in two parallel strings each consisting of 5 Nomura MPPTs. Ideal diodes are used to prevent the strings from back feeding each other. The output voltage limit of each MPPT is set such that the maximum voltage of each strings is equal to the max charge voltage of the HV battery, allowing a direct connection to the pack.
Low Voltage
Battery Protection and Management
BMS Carrier
The BMS system consists of 3 board variants:
BMS Current Sense - Monitors pack current and calculates SoC with a fuel gauge IC.
BMS AFE - Measures
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Project | Summary |
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Controller Board | The “brain” of the boards; all boards that require ‘decision making’ or firmware-controlled inputs or outputs will have a controller board | Power Distribution | This board controls the power flow of all other devices in the car. It chooses who gets power, where the source of the power is, and monitors the power drawn Power Select: selects the power source that the car draws power from. It selects between the AUX (usually used only for fans, horn, telemetry, main contactor relays), and DCDC (LV power from main pack) Power Distribution: contains many firmware-controlled load switches that deliver power to all other boards/devices on the vehicles (boards, fans, horn, lights, etc). Also monitors the current draw for each load. Contains many connectors for other boards to plug into | | Disconnects the battery if the voltage falls below a certain threshold. Provides additional protection features, including | Centre Console | Serves as the hub of communication between the driver and the car. Displays useful information (speed, battery state, left/right turn signals, Battery Protection System warnings) to the driver in the form of LEDs and 7-segment displays. It also receives input from 6 buttons, allowing the driver to Power On the vehicle, switch drive states (Drive, Neutral, Reverse), and enable/disable regen braking and hazard lights. | Motor Controller Interface (MCI) | Talks to motor controllers, we control the motors/get motor information through this board. | BMS Carrier | This board is responsible for protecting the battery. Its responsibilities are: Logging Voltage, Current, Temperature Calculating the state of charge Detecting battery faults and acting upon them
| BMS AFE | Used to measure cell voltage and temperatures from each individual battery module, and also keep the cells balanced | BMS Current Sense | Measures the total current flowing from the battery pack. | DCDC | Converts the high voltage (110-150V) to the necessary low voltage of 12V nominal (ends up being 13-14V) | Pedal | Measures the angle of both pedals in the car (accelerator and brakes). This information is used to know how much each pedal is pressed, and then use this information to execute some functions (e.g if the accelerator is not pressed then regen braking will occur; if brakes are pressed, then brake lights should turn on) | Steering | Used for measuring steering angle as well as controls present on the stalk (lights, signals, horn). | Solar Sense/MPPTs | Solar sense: Measures the array module and array voltage, temperature, current MPPT: Converting high current low voltage output from the solar panels into low current high voltage power compatible with our batteries and motors | Steering Stalk | The physical steering stalk that the driver uses, taken off an old vehicle, currently in the bay. It contains its own circuitry that must be understood such that we can interface with it and understand how to read its inputs. | Motor Testing | To test the motor and motor controller work correctly | Electrical Systems PVDR/VDR | Comprehensive design report including technical documents mechanical systems, electrical systems, batteries, and solar cells. |
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