Protection Systems
ASI BAC controllers include comprehensive protection systems to prevent damage to the controller, motor, battery, and vehicle.
Faults vs Warnings
| Type | Behavior | Severity |
|---|---|---|
| Faults | Disable motor operation | Critical - requires resolution |
| Warnings | Reduce performance (foldback) | Protective - auto-recovers |
Fault Conditions
Faults are stored at Address 258 as a 16-bit register. Each bit represents a different fault condition.
Critical Faults
| Flash Code | Fault | Description |
|---|---|---|
| 1,1 | Slow over voltage | Filtered battery voltage exceeded threshold for >1 second |
| 1,2 | Phase overcurrent | Motor phase current exceeding thresholds |
| 1,5 | Controller overtemp | Controller temperature exceeded safe limits |
| 1,6 | Hall sequence error | Motor Hall sensor sequence invalid |
| 1,7 | Slow under voltage | Battery voltage below minimum for >1 second |
| 2,1 | Network timeout | Network communication timeout |
How to Clear Faults
Most faults clear by:
- Rebooting the controller (power cycle)
- Reducing the triggering condition (temperature, voltage, current)
Flash Code Reading
The LED uses dual-digit flash patterns: first digit flashes, short pause, second digit flashes, long pause, then repeats. Example: "1,1" = one flash, pause, one flash, long pause.
Warning Conditions
Warnings are stored at Address 277 and indicate protective foldbacks activating:
| Warning Bit | Condition | Action |
|---|---|---|
| Bit 7 | Low battery voltage | Current reduction active |
| Bit 8 | High battery voltage | Regen reduction active |
| Motor temp | Motor overheating | Performance reduction |
| Battery SOC | Low state of charge | Current reduction |
| I²T overload | Thermal accumulation | Current limiting |
Controller Temperature Foldback
The controller has two integrated temperature sensors:
- Powerboard sensor: Monitors MOSFETs
- DSP sensor: Monitors digital signal processor
Temperature Thresholds
| Parameter | Function |
|---|---|
| Controller Foldback Starting Temperature | Peak motor current reduction begins |
| Controller Foldback Ending Temperature | Peak motor current reduced to 0A |
Fixed Parameters
Controller temperature thresholds are manufacturer-set and cannot be modified by users.
Behavior
As temperature rises:
- Current limit progressively reduces
- At ending temperature, motor output stops
- Cooling allows gradual recovery
Motor Temperature Foldback
Protects motors from thermal damage to internal electronics, mechanical components, and magnet demagnetization.
Configuration
| Parameter | Function |
|---|---|
| Motor foldback starting temperature | Current reduction begins |
| Motor foldback end temperature | Peak current reduced to 0A |
Temperature Sensor Setup
- Activate
Features bit 5(Motor temp sensor enable) - Select the
Motor temperature source - Input voltage values at six temperature points:
- 0°C, 25°C, 50°C, 75°C, 100°C, 125°C
Temperatures above 125°C and below 0°C use linear extrapolation.
Sensor Types
| Type | Behavior |
|---|---|
| NTC | Resistance decreases as temperature rises |
| PTC | Resistance increases as temperature rises |
Wiring Options
Connect thermistor to:
- Throttle/Analog Input 1
- Brake1/Analog Input 2
- Brake2/Analog Input 3
- ABMS/Analog Input 4
Firmware Note
Firmware 6.022 and earlier restricts NTC sensors to Brake2/Analog Input 3 only.
Motor I²T Foldback
Thermal accumulation monitoring protects against overheating even without a temperature sensor.
Heating Setup
The overload accumulator builds when motor current exceeds continuous rating:
| Current Level | Gain | Behavior |
|---|---|---|
| Below continuous | 0 | No accumulation |
| Continuous to heating | 0-1 | Linear accumulation |
| Above heating | 1 | Full accumulation rate |
Overload heating time: Duration to reach 100% accumulation at full gain.
Cooling Setup
The accumulator decreases when motor current drops below cooling threshold:
| Current Level | Gain | Behavior |
|---|---|---|
| Below cooling | 1 | Full cooling rate |
| Cooling to continuous | 0-1 | Linear cooling |
| Above continuous | 0 | No cooling |
Overload cooling time: Duration to reach 0% accumulation at full gain.
Reset Behavior
Restarting the controller resets the accumulator to 0%.
Foldback Implementation
| Parameter | Function |
|---|---|
| Overload foldback start | Begin reducing motor current |
| Overload foldback end | Eliminate all motor current |
Current reduction interpolates linearly based on accumulator percentage.
Battery I²T Foldback
Similar to motor I²T but monitors battery current instead.
Enable by: Setting Motor Features bit 3 to "Disable motor I²t enable battery I²t"
Uses the same heating/cooling time constants and accumulator thresholds as motor I²T.
Speed-Based Foldback
Adjusts motor torque based on vehicle speed to protect the motor and controller at high speeds.
Configuration Process
- Slope Calculation: System computes slopes between power map setpoints (addresses 157-164)
- Speed Mapping: Vehicle speed compared against speed limit setpoints (addresses 165-172)
- Foldback Application: Based on current speed range, applies calculated power reduction
Voltage Protection Details
Overvoltage Protection
| Address | Parameter | Behavior |
|---|---|---|
| 147 | Fast over voltage | Single spike above threshold → immediate trip |
| 149 | Slow over voltage | Averaged voltage above threshold for >1 second → trip |
Fast OVP (Faults bit 12): Cannot be disabled, only adjusted up to controller input rating.
Slow OVP (Faults bit 0, Flash code 1,1): Bridge disables until voltage drops below threshold for >1 second.
Undervoltage Protection
| Address | Parameter | Behavior |
|---|---|---|
| 148 | Fast under voltage | Single dip below threshold → immediate trip |
| 150 | Slow under voltage | Averaged voltage below threshold for >1 second → trip |
High Battery Voltage Foldback
| Address | Parameter | Function |
|---|---|---|
| 194 | High battery foldback starting voltage | Regen current reduction begins |
| 195 | High battery foldback end voltage | Maximum regen reduction |
Warning bit 8 activates when voltage exceeds starting threshold.
Low Battery Voltage Foldback
| Address | Parameter | Function |
|---|---|---|
| 141 | Low battery foldback starting voltage | Discharge current reduction begins |
| 142 | Low battery foldback end voltage | Maximum discharge reduction |
Warning bit 7 activates when voltage falls below starting threshold.
POST (Power-On Self-Test)
The POST performs diagnostic checks each time the motor is enabled.
Static Gating Test
Measures voltage across three motor phases before bridge activation:
Pass criteria: Three voltages must measure 50% (±25%) of battery voltage.
| Address | Parameter |
|---|---|
| 285-287 | Phase A, B, C voltages |
| 47 | Open circuit voltage test window |
| 306-308 | Phase U, V, W POST readings |
Dynamic Gating Test
If static test passes, PWMs individual FETs sequentially:
Pass criteria:
- Low side: 15% (±10%) of battery voltage
- High side: 85% (±10%) of battery voltage
| Address | Parameter |
|---|---|
| 48 | High/Low-side turn on voltage test window |
| 300-305 | High/low voltage POST measurements |
Firmware Requirement
Open circuit voltage test window modification requires firmware 6.023+ with access level 1 unlocked.
Hall Stall Fault
Monitors motor operation for stall conditions.
Detection
When output exceeds 20% of rated motor current without corresponding position changes, the controller generates warning bit 2.
Configuration
Set Hall stall fault time to a non-zero millisecond value to activate monitoring.
Tuning Caution
Setting Hall stall fault time too low can cause false faults during throttle engagement. Tune carefully to prevent nuisance warnings.
Troubleshooting Approach
Most protection issues resolve through:
- Parameter verification - Check configuration values
- Hardware inspection - Wiring, connections, components
- Temperature management - Cooling, airflow, duty cycle
- Battery condition - Voltage, capacity, internal resistance
Required Tools
- Safety equipment (glasses, ESD mat)
- Current-limited power supply (48V max)
- Digital multimeter
- BACDoor software
- USB isolator
Testing Checklist
- Visual inspection for damage
- Short check between terminals
- Power-up with current limiting
- Peripheral verification (voltage outputs)
- CAN bus testing (if applicable)
- POST static/dynamic testing
Next Steps
- Configure Battery Settings for proper limits
- Set up Communication for monitoring
- Review Software Tools for diagnostics