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FrontRear

Peripheral Displays & Cameras

(Use a simple circuit to distribute the current) 

Solar Master (Front)
Steering BoardSolar Master (Rear)
Pedal BoardRear View Camera
FanFan
SpareTelemetry
SpareCharger Interface

Potential Parts

Part NumberLoad CurrentRds OnNumber of OutputsAnalog Current Sense
TPS2H160BQPWPRQ12.5A155mOhm2
BTS71202EPAXUMA12A61mOhm2+/-30% @ 50mA, +/-11% @ 500mA
AUIPS7091GTR1.5A80mOhm1+/-8% @ 50mA, +/-3% @ 500mA
AUIPS7081RTRL2A55mOhm1

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FrontRear
Front Lights BoardMotor Interface
Center ConsoleRear Lights Board
Horn? (8A)Spare

Potential Parts

Part NumberLoad CurrentRds On
BTS70401EPAXUMA14.5A19mOhm
BTS70081EPPXUMA111A8.8mOhm
BTS70061EPPXUMA112A6.6mOhm

High-Current HSD

Current Limit: < 20A @ 12-13.5V

FrontRear

Spare

Front Power Distribution

(around 16A at the maximum)

Spare

BMS Carrier (Master & Slave)

(due to high inrush current to the relays)

Potential Parts

Part NumberLoad CurrentRds OnCurrent Mirror Error
BTS70041EPPXUMA115A4.4mOhm± 8% @ 10 - 15A
AUIR3313STRL23A (Adjustable)

Front Power Distribution

(around 16A at the maximum)

5.5mOhm± 5%
BTS70021EPPXUMA121A (Fixed)2.6mOhm± 5%

Medium-High-Current HSD

Current Limit: 6 - 20A @ 12-13.5V

Potential Parts

Part NumberLoad CurrentRds OnAnalog Current SenseNote
TPS2HB08BQPWPRQ16.4A - 70A (Adjustable)8mOhm±15% @ > 0.5AFound on Mouser

Supplemental Battery

MS12 use a 12 V 10-cell? NiMH battery as the supplemental battery. It is used to power the minimal necessary systems to check the battery system and the reset of the car before closing the main battery relays.

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Since the loads are parallel, they should operate at the same voltage. The PWR board only needs to measure the output voltage of the supplemental battery and the DC-DC converters

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Current Sensing

Accuracy

The main benefit purpose of high-side current sensing is the ability to detect a short circuit in the load or the harness. There are few solutions to current sensing:

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the current sensing is understanding how much power is being used by each system while the car is driving/racing. The data will be used to identify systems with high power usage for future optimization. It is more meaningful to track the power consumption of each system relative to the total power rather than the absolute value.

The target power consumption of MSXIV's LV system is 20 W. A reasonable accuracy will be the +/- 0.1% of the total power. Given the supply voltage will be 12-13.5 V, the current sensing circuit should be more accurate than +/-  1.5 mA.

Locations

Given the HSD will be responsible for disconnecting the load when it is shorted to ground, there is no safety advantage for high side current sensing. There are three locations for the current sense resistor:

  • Low-Side
    • Easier to implement
    • Requires a 100 mOhms current sense resistor which consumes some power
  • High-Side
    • High immunity to ground disturbance
    • The common-mode voltage tolerance of the differential op-amp must be greater than 12V
  • HSD Current Mirror
    • A HSD built-in current mirror with high gain plus a current sense resistor should use less power than the low-side sensing (needs proof)
    • The accuracy is around +/- 30% for low current (< 100 mA)

Block Diagram

Image Added

Ports

Front

BoardNom. Current (A)Max. Current (A)ConnectorHSD
Peripheral Displays & Cameras0.2780.329
Light
Front Lights Board1.8894.163
Heavy
Steering Board0.0170.071
Light
Pedal Board0.0130.067
Light
Center Console0.9522.146
Light
Horn08
Heavy

Rear

BoardNom. Current (A)Max. Current (A)ConnectorHSD
Motor Interface0.1794.958
Light
BMS Carrier (Master & Slave)0.81419.800
Heavy
Solar Master0.1500.482
Light
Rear Lights Board0.0222.879
Heavy
Rear View Camera0.50.5
Light
Charging Interface0.0260.133
Light
Front Power Distribution 3.25015.97
Heavy