Braking Systems

ASI BAC controllers support three braking modes that work together to provide smooth deceleration and energy recovery.

Overview

Braking Mode	Description	Energy Recovery
Regenerative	Manual brake input converts kinetic energy to charge	Yes
Engine Braking	Off-throttle deceleration with energy recovery	Yes
Plug Braking	Active low-speed braking using battery power	No (uses power)

Safety Warning

Regenerative and plug braking should not be used as the sole source of braking. They should only supplement a functioning mechanical braking system.

Regenerative Braking

Electric motors function as generators when driven externally. The controller converts kinetic energy into electrical energy to recharge batteries while reducing mechanical brake wear.

Wiring Setup

Regen brake sources connect to:

Brake1/Analog input 2
Brake2/Analog input 3

Signal types supported:

Digital: On/off switching
Analog: 0-5V proportional control

Configuration Steps

Set Battery Current Limit

Calculate as: Peak regen current ÷ (Rated motor power ÷ Rated system voltage)

Example: 45A regen on 2880W/48V system = 45A ÷ 60A = 75%

Enable Regen

Set Features bit 4 (Regen braking enable) to 1.

Select Source

Choose from: Brake2, Brake1, Network, Throttle, or ABMS as the regen brake source.

Enable Pullup

Enable the corresponding pullup resistor for your selected input.

Set Maximum Braking Torque

Start conservatively at 10% of rated motor current to prevent skidding.

Configure Voltage Thresholds

Set Analog brake off voltage and Analog brake full voltage to match your input device.

Adjust Deadband

Set Analog Brake Deadband Range appropriate to your application.

Typical Input Values

Input Type	Off Voltage	Full Voltage
Digital	4V	1V
Analog	0.9-1.2V	3.9-4.2V

Key Parameters

Parameter	Function	Recommendation
Maximum braking torque	Total available braking force	Start at 10%
Positive braking ramp	Responsiveness to input	200ms minimum
Negative braking ramp	Release speed	Application-dependent
Regen brake speed	Minimum speed threshold	Set above low-speed cutoff

Brake Setpoint

Range: 0.0 (no braking) to 1.0 (maximum braking)
Regen current flows automatically based on setpoint

Low Speed Limitation

Regen braking becomes ineffective at low speeds due to insufficient back-EMF. Use plug braking to supplement.

Engine Braking

Engine braking (off-throttle regen) captures kinetic energy during deceleration when the throttle is released.

Configuration Steps

Enable the Feature

Activate Features bit 13 for engine braking.

Set Battery Current Limit

Configure Regeneration battery current limit as a percentage.

Formula: Peak regen current ÷ (Rated motor power ÷ Rated system voltage)

Set Maximum Braking Torque

Define Maximum braking torque as a percentage of rated motor current. Start at 10% to understand the effect.

Set Engine Braking Torque

Configure Engine braking torque as a percentage of maximum braking torque.

Interaction with Manual Regen

As of firmware 6.014, when both engine braking and analog regenerative braking are active simultaneously:

The controller gives priority to whichever source is commanding the higher braking torque.

Torque Ramp Configuration

Parameter	Function	Recommendation
Positive braking torque ramp	Controls responsiveness	200ms minimum to prevent wheel lockup
Negative braking torque ramp	Determines release speed	Application-dependent

Plug Braking

Plug braking is a reverse current braking mechanism that supplements regenerative braking at low RPM where regen struggles due to insufficient back-EMF.

How It Works

The system draws battery power to inject opposing current, helping decelerate the motor to a stop.

Configuration

Feature bit: Features2 bit 3

State	Behavior
Disabled	Controller won't draw battery power at low speeds; motor won't actively stop
Enabled	Controller draws battery power at low speeds to actively decelerate

Regen Brake Speed Parameter

The Regen brake speed parameter establishes the minimum threshold:

Plug braking activates above this speed limit
Below this speed, plug braking is not effective

Cutout Brake

The cutout brake feature prevents motor engagement during local operation using a switch.

Wiring Options

Connect a single-throw switch to:

Cruise/Digital Input 1
PFS/Digital Input 2
Brake 1
Brake 2

Digital inputs are internally pulled up - wire switch between GND and the input. Analog brake inputs require an external pull-up resistor.

Setup

Select the Cutoff brake sensor source at address 248
Enable the brake
Verify ebike flags bit 1 shows Cutout as active

ABS/Braking Traction Control

This feature enhances braking stability by dynamically modifying braking current in response to sudden deceleration.

How It Works

Threshold Calculation:

Threshold (s) = 100 / (Rated Motor RPM × Motor Pole Pairs)

Brake Response Logic:
- Transition time > threshold → Braking current drops to zero (releases brake)
- Transition time ≤ threshold → Normal braking current applies
Automatic Operation: Brake releases during sudden deceleration and reapplies when motor speeds up.

Enable

Activate Features 3 bit 13: Enabled ABS/Traction control

High Battery Voltage Foldback

When the battery approaches full charge, regen current must be reduced to prevent overvoltage.

Address	Parameter	Function
194	High battery foldback starting voltage	Regen reduction begins
195	High battery foldback end voltage	Maximum regen reduction

Warning bit 8 activates when voltage exceeds the starting threshold.

Disable Option

Set thresholds out of range to disable high battery foldback.

Bidirectional Throttle

Available in firmware 6.025+, this feature allows one side of the throttle for forward driving and the other for braking or reverse.

Setup Steps

Configure throttle sensor source
Set Throttle full voltage for forward direction
Set Throttle off voltage for reverse/brake direction
Configure Throttle fault range for fault detection
Set Throttle deadband threshold
Configure midpoint (parameter 1987)
Set neutral zone width (parameter 1988)
Assign Reverse_Enable_Source and/or Regen brake source to '4'
Enable Features4 bit 11

Configuration Summary

Recommended Starting Values

Parameter	Starting Value	Notes
Regeneration battery current limit	20-50%	Higher for more regen
Maximum braking torque	10%	Increase gradually
Engine braking torque	20-50%	Of max braking torque
Positive braking ramp	200ms	Prevents wheel lockup
Regen brake speed	5 km/h	Minimum effective speed

Interaction Priority

When multiple braking sources are active (firmware 6.014+):

Compare commanded braking torque from each source
Apply the highest commanded torque
Respect battery current limits

Next Steps

Configure Battery Settings for proper voltage limits
Set up Protection Systems for safe operation
Review the Technical Q&A for common questions

Braking Systems

Safety Warning

Set Battery Current Limit

Enable Regen

Select Source

Enable Pullup

Set Maximum Braking Torque

Configure Voltage Thresholds

Adjust Deadband

Low Speed Limitation

Enable the Feature

Set Battery Current Limit

Set Maximum Braking Torque

Set Engine Braking Torque

Disable Option

Related Articles

Battery Configuration

Motor Setup

Parameter Dictionary