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Goals
- Isolate ADC
- Interface with Nomura MPPT
- Record voltage and temperature per-module and current per-string
Background and strategic fit
We're planning on using Nomura MPPTs. Each MPPT is designed to connect to a smaller number of cells and output up to around 30V. A few of these MPPTs are then put in series. Theoretically, this should maximize the performance of our array in non-optimal conditions.
We're like to record data on the array to optimize our strategy and charging.
Assumptions
- Our MPPTs will output around 30V at max
- Our array should generate around 1kW at max
- Our MPPTs will be integrated into the array modules
- We will need to deal with communications over 1m+ cables
Requirements
| # | Title | User Story | Importance | Notes |
|---|---|---|---|---|
| 1 | Work with Nomura MPPTs | We're using 10 Nomura MPPTs, 5 in series for 2 strings total. They don't have any public way of interfacing with them, but we'd like to collect data on our array. | Must Have | Using a master board for current sensing and LIN slaves for each MPPT |
| 2 | Record voltage and temperature per-module | We'd like to know the voltage and temperature of each module so we can tell how each module is performing and any potential hotspots. | Must Have | |
| 3 | Record current per-string | We'd like to know the current provided by each string so we can calculate the overall power of the solar array. | Must Have | We will probably use a dedicated current slave to record the current of the string. |
| 4 | Isolated | We want to make sure that our analog measurement is isolated from the rest of the car. | Must Have | Look into analog isolation using a class D amplifier + digital isolator |
| 5 | Low-cost/Simple | We'd like to make these boards as simple as possible to reduce development time. | Must Have | Once the LIN stack is written, we can use the built-in ADC to record voltage and temperature. |
Questions
Below is a list of questions to be addressed as a result of this requirements document:
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