FarDriver: Battery Limits and Cutouts

A FarDriver can ask for more current than the battery can deliver. If the bike cuts out under hard acceleration but works at lighter loads, check battery demand, voltage sag, and BMS protection before increasing controller output.

Battery Behavior and Current Limits (Critical Power Limitation)

Battery performance directly limits how much power the system can deliver.

The controller does not create power - it requests it from the battery through MaxLineCurr.

If current demand exceeds battery or BMS capability, the system will cut power regardless of controller settings.

Why This Happens

MaxLineCurr defines total current draw from the battery.

If this value is set higher than the battery can safely supply:

• voltage will sag under load
• BMS protection may trigger
• output will shut down or reset

This is normal protective behavior.

Failure Modes

BMS Overcurrent Protection

• battery shuts off output instantly
• system loses power under heavy throttle
• power returns after throttle is released or system resets

Voltage Sag Cutoff

• voltage drops below LowVoltProtect under load
• controller reduces or cuts power
• feels like sudden power loss at high demand

Thermal Limiting (Battery or Wiring)

• sustained high current increases heat
• resistance increases -> more voltage drop
• leads to earlier cutoff or instability

Real-World Symptoms

Battery limitation commonly appears as:

• bike cuts out at high throttle
• runs normally at low and mid throttle
• power returns after releasing throttle
• no persistent controller fault
• behavior worsens at lower battery charge

This is frequently misdiagnosed as:

• controller failure
• throttle issues
• bad tuning

Critical Relationship

• MaxLineCurr -> battery load (total power)
• MaxPhaseCurr -> motor torque (heat)

Increasing MaxLineCurr:

• increases power draw
• increases battery stress
• increases likelihood of BMS cutoff

Diagnostic Method

1. Apply gradual throttle under load
2. Observe behavior:

• smooth -> stable system
• sudden cutoff -> battery or BMS limit

3. Repeat at different charge levels:

• worse at low voltage -> confirms battery limitation

Correct Adjustment Strategy

• set MaxLineCurr within battery continuous capability
• increase incrementally
• monitor:
  • voltage sag
  • system stability
  • connector temperature

Do not exceed what the battery can sustain.

What Not To Do

Do not attempt to fix battery limitations by:

• increasing Phase Current
• modifying throttle settings
• changing unrelated tuning parameters

These do not increase available battery power.

Calibration Rule

If the system cuts out under load:

• verify battery capability first
• reduce MaxLineCurr if necessary
• confirm stable operation before increasing again

Priority

This is a Critical Power Limitation.

If present, it must be resolved before:

• increasing performance
• applying aggressive tuning
• extended high-load operation

Ignoring this can result in:

• repeated BMS shutdown
• connector damage
• battery stress or failure

⚠️ Battery Cutout vs Controller Behavior (MaxLineCurr)

MaxLineCurr directly controls how much current is drawn from the battery.

If this value exceeds the battery or BMS capability, the system may:

• shut off abruptly under load
• cut power at high throttle
• reset or recover after releasing throttle or cycling power

This is not a controller fault.

This is the battery or BMS protecting itself from overcurrent.

Controller Current Capability (ND Series)

These values define the safe operating range of ND96680 and ND961000 controllers and apply across 72V, 84V, and 96V systems. Voltage does not change current limits, but higher voltage increases total power at the same current.

ND680

ND1000

Common Symptoms

• bike runs normally at low and mid throttle
• cuts out only under heavy acceleration
• returns to normal after throttle is released
• no persistent controller fault codes

Critical Understanding

Increasing MaxLineCurr increases total power draw.

If the battery cannot supply that current:

• voltage sag increases
• BMS protection may trigger
• system power will be cut

This behavior can feel like:

• random shutdown
• throttle failure
• unstable tuning

But the root cause is current demand exceeding battery limits.

Do not attempt to fix this by:

• increasing Phase Current
• adjusting throttle settings
• modifying other tuning parameters

These do not solve battery limitations.

-> See ONYX Jaws Mode Calibration -> Battery Behavior and Current Limits before increasing MaxLineCurr further.