Credit: Ross Krasnow

ONYX Variable Regenerative Braking

This setup, featuring a 12V signal relay module and an analog output brake lever, transforms the braking experience by replacing the abrupt regen switch with smooth, variable regen control. It retains the functionality of the brake lights and motor stop while minimizing mechanical brake wear by engaging the pads only at the final stage of the lever pull.

Variable Regenerative Braking Parts

Variable Regen

Connecting a Fully Functional Variable Regen Brake Lever

Goal:

  • Create a left brake lever setup that:
  • Sends a variable regen signal to the controller for analog regen control.
  • Activates the brake light and motor stop functionality.

Setup

Controller Pins:

Pin 25 (Yellow wire):

  • 12V brake switch input.
  • Triggers brake light and motor stop.
  • Default: Connected to 12V line from Pin 11.
  • Recommended: Connect to 12V from a buck-boost converter for brighter brake light performance.

Pin 2 (Brown wire):

  • Analog brake input.
  • Receives variable regen signal from the brake lever.

Pin 3 (Green wire):

  • 5V output for throttle.
  • Tap this to supply 5V to the variable regen brake lever.

Pin 20 (Ground):

  • Ground connection for the throttle.
  • Any ground can be used.

Wiring Instructions

Variable Regen Wiring:

Analog Regen Input:

  • De-pin Pin 2 (brown wire) from the controller.
  • Connect it to the variable input wire of the regen lever (e.g., blue wire for Grin lever).

5V Power Supply:

  • Tap into Pin 3 (5V output).
  • Run this wire to the brake lever’s 5V input (e.g., red wire for Grin lever).

Ground Connection:

  • Connect the brake lever ground to Pin 20 or any other available ground.
  • You can run this from the throttle ground for simplicity.

Brake Switch Wiring:

The brake lever uses a hall sensor instead of a physical switch, so a relay is required.

Relay Wiring:

  • Connect the 12V line from the buck-boost to VCC on the relay.
  • Connect the ground from the buck-boost to GND on the relay.
  • Connect the yellow sensor wire from the brake lever to the Input pin on the relay to trigger it.
  • Connect Pin 25 (controller) and 12V from the buck-boost to COM1 and NO1 on the relay.
    • This ensures the brake light and motor stop are triggered when the relay is activated.

Controller Settings

Disable Regen with Switch:

  • Set BRK_SW = 0.

Enable Variable Regen:

  • Set Brake Type = 1 (or try Brake Type = 2).

Maximize Variable Regen Braking:

Set BRK_AD = 50.

Tune Brake Dead Zones:

  • Use a multimeter to measure the lever voltage range:
  • Lever idle: ~0.9V.
  • Lever fully engaged: ~3.9V.
  • Relay triggers at ~1.3V.

Adjust Dead Zones:

  • Brake Dead Low = 26% (1.3V ÷ 5V).
  • Brake Dead High = 78% (3.9V ÷ 5V).

Mechanical Rear Brake Adjustment

  • Set the mechanical brake line to activate only at the last 5–10% of lever pull.
  • Adjust the small pin on the brake to fine-tune braking strength.

ONYX Variable Regenerative Braking Images

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