...
The purpose of this confluence page is so that electrical members may review my calculations.
Specifications:
The battery shall be able to energize protected LV systems until the main battery is energized
...
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.
Electrical Characteristics:
Energy Budget:
To characterize energy capacity, we will group loads into 3 sections:
...
Required (nominal) capacity: 12.83025 Ah
Power Budget:
Load | Description | Power Demand – Typ [W] | Power Demand – Peak [W] |
|---|---|---|---|
Telemetry | Raspberry Pi (Assuming switching regulator at 90% efficiency to downregulate 12V to 5V power) | 2.5 | 2.5 |
Fans | 10.2W – Point estimate | 10.2W – Point estimate | |
Contactors | 3 Contactors – 3-5A | 3.5W – Typical | 180W – Initial closing |
Emergency LV Power | In case of BPS fault | 54.111 | 130.630W |
Horn | 7W horn | 7 | 7 |
Peak power necessary on startup | Telemetry, Contactors, Fans | 192.7 | |
Peak power necessary when phase 2 or 3, normal operation | Telemetry, Contactors, Fans | 16.2 | |
Power necessary on BPS fault (if no need to re-close contactors): | Fans, Contactors, Emergency LV Power (incl. telemetry), Horn | 74.81100 | 151.33 |
Peak power necessary on BPS fault (if yes need to re-close contactors): | Telemetry, Fans, Contactors, Emergency LV Power (incl. telemetry) Horn | 251.31100 | 327.83 |
...
Current – Peak on BPS fault & MPS must be re-opened: 27.32 A
Things to Verify:
Contactor Loads
Horn Loads
Chances of being constant 7W is kind of low? What’s peak current demand?
Telemetry Loads
How long do we need emergency power for on BPS fault?
What’s an acceptable S.F?
...
Will the MPS ever need to be opened again after it has been closed?
Pack Arrangements:
10s1p | 10s2p | 10s3p | |
|---|---|---|---|
Watt-hours (rated) | 120 | 240 | 360 |
Watts | 120 | 240 | 360 |
Energy Loads | |||
Persistent loads met? | No | 1.65 S.F. | 2.47 S.F. |
Persistent + 5 mins emergency loads met? | No | 1.56 S.F | 2.34 S.F. |
Power Loads | |||
Typical Phase 2 or 3 | 7.41 S.F | 14.81 S.F. | 22.22 S.F. |
Peak Startup | No | 1.25 S.F. | 1.87 S.F. |
Typical BPS fault | 1.6 S.F. | 3.2 S.F. | 4.8 S.F. |
Peak BPS fault | No | 1.59 S.F | 2.38 S.F. |
Typical BPS Fault & MPS Re-energization | No | No | 1.43 S.F. |
Peak BPS Fault & MPS Re-energization | No | No | 1.1 S.F. |
Runtime [hrs] | 7.4 | 15 | 22 |
Mass (of cells) [kgs] | 1.45 | 2.90 | 4.35 |
Resistance (of cells, nominal) [mOhm] | 18 | 9 | 6 |
Conclusions:
It is evident that 10s1p is insufficient to run all aux loads for one race day
10s2p contains enough energy for one race day and can supply enough power for all loads calculated (if loads are correct), however cannot re-energize the MPS if it is de-energized, must power the LV loads and must be re-energized. This is likely not necessary, as the car has to pull over and fix the BPS fault before continuing, as per regs. The safety factor for capacity is 1.65, which may or may not be sufficient, as thermal effects, parasitic resistances, and future alterations to loads may increase the required capacity.
Please verify if the loads are correct?
Mechanical Characteristics
Thermal Constraints
(TBD)
(Make sure the busbars don’t get so hot that the plastic melts, or that the module can withstand such heat)
...