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Goals
- Design a BMS that is robust to electrical noise found from sources in and out of vehicle
- The BMS is robust and reliable to vibration, elements, and users
- The BMS provides test points for scrutineering
- The BMS is calibrated appropriately
- Provides at least the minimal active protection requirements for the Li-ion battery pack
- Over-voltage
- Under-voltage
- Over-temperature
- Over-current (either direction)
- Transmit voltages, current, temperatures, and SOC to telemetry/display
- Consider manufacturability and flexibility
Background and strategic fit
The Battery Management System (BMS) is responsible for monitoring the state our Li-ion pack, ensuring that the battery is operating within its Safe Operating Area, calculating secondary data, reporting that data, and balancing it. It consists of Analog Front-End chips that allow the board to grab pack data, and then take appropriate actions.
MSXI's BMS was a single board that had 6 AD7280As and a hall-effect current sensor. This approach was difficult to manufacture and test, as bringing up a board was expensive and error-prone. It was also physically large, which made it difficult to fit in the battery box. Also, all the wires needed to return to the single board, making wiring a challenge.
Requirements
| # | Title | User Story | Importance | Notes |
|---|---|---|---|---|
| 1 | Minimize wiring | We'd like to reduce the amount of wiring that needs to be run back to the controller board. | Must Have | Look into splitting AFEs into their own boards |
| 2 | Flexible setup | We haven't fully decided on our battery box layout, so the voltage and number of AFEs required is subject to change. | Must Have | Daisy chained AFEs would make this nice |
| 3 | Cell balancing | It'd be nice to be able to support cell balancing. | Optional | We're building a new pack and we should be testing our modules to match capacity |
Questions
Below is a list of questions to be addressed as a result of this requirements document:
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