Replaceable batteries required to power some components of the car. (Need to update this more)
Supplemental Battery Constraints:
The battery shall be able to energize protected LV systems until the main battery is energized
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The battery cannot overheat
Voltage:
Nominally 12V, however voltage levels should not be altogether too significant as voltage is further downregulated to logic levels on each individual board.
Energy Capacity:
Load | Description | Energy Demand |
|---|---|---|
Horn | Horn must be able to be run for 5 minutes in an emergency | 9 Wh |
Emergency Telemetry | Assume 2.5W for a raspberry pi, 8 hr race day (super over-the-top) | 20 Wh |
Driver Fans | 1 Noctua NF-F12 iPPC 3000, 3.6W max (Reused from MSXIV), 8 hrs (Asked Nita) | 28.8 Wh |
Total | 57 Wh |
Required Capacity: 4.9 Ah
Current Demand:
Load | Description | Current Demand |
|---|---|---|
Horn | Direct driven 12V horn | 9A |
Telemetry | Raspberry Pi (Assuming switching regulator at 90% efficiency to downregulate 12V to 5V power) | 0.56 A |
Fans | 1 Noctua NF-F12 iPPC 3000, 3.6W max (Reused from MSXIV), typ. current of 0.26 A, max of 0.3A | 0.3A |
Contactors | 3-5A | 5A |
Constant Discharge Rate | 0.86A | |
Maximum Discharge Rate (Startup) | Maximum discharge rate to energize contactors | 5A |
Maximum Discharge Rate (Horn) | Maximum discharge rate from all emergency systems + horn | 9.86A |
Battery Choices
Batteries investigated over multiple areas are found in the attached file.
| View file | ||
|---|---|---|
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Final Battery Choice
The final battery chosen is the Maha Powerex Precharged 10000mAh D cell battery in a string of 10 cells, as it has already been purchased. It has a capacity of 120Wh, and can deliver an approximate maximum constant discharge rate of 10A (verified via call to Maha)
Thermal Constraints
As the D cell battery has an internal resistance of 18mOhm at full discharge, the maximum heat generation will be 2.0072448W for 5 minutes, assuming the horn is running.
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(module design coming later)
Amendment to Battery Constraints – 2023-07-19:
Energy Capacity:
Load | Description | Energy Demand |
|---|---|---|
Horn | Horn must be able to be run for 5 minutes in an emergency | 9 Wh |
Telemetry | Assume 2.5W for a raspberry pi, 8 hr race day | 20 Wh |
Driver Fans | 1 Noctua NF-F12 iPPC 3000, 3.6W max (Reused from MSXIV), 8 hrs (Asked Nita) | 28.8 Wh |
Total | 57 Wh |
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