Battery Current Max Regen

Battery Current Max Regen is a setting in VESC Tool that defines the maximum regenerative current the controller is allowed to return to the battery during braking.

Because regenerative current flows back into the battery, Battery Current Max Regen is entered as a negative value. Increasing the magnitude of this value allows more regenerative braking energy to be returned to the battery, while reducing it limits battery charging current during braking.

⚠️ Battery Current Max Regen is not the same as Motor Current Max Brake. Battery Current Max Regen limits the charging current flowing into the battery, while Motor Current Max Brake limits the braking current flowing through the motor windings and therefore determines the available braking torque.

Because the controller acts as a power converter, Motor Current Max Brake can often be significantly higher than Battery Current Max Regen. This allows strong braking torque while limiting the charging current seen by the battery.

Battery Current Max Regen should be selected based on:

• Battery charge current rating
• Battery chemistry
• Cell configuration
• BMS charge current limits
• Wiring and connector ratings
• Number of controllers connected to the battery
• Desired regenerative braking performance

⚠️ Battery Current Max Regen should never exceed the peak charging current rating of the battery system. This includes the battery cells, BMS, wiring, connectors, fuses, and any other components carrying regenerative current.

⚠️ When multiple controllers share the same battery, the combined Battery Current Max Regen values should not exceed the battery system charging limits. For example, if a battery and BMS are rated for 20A continuous charging current and two controllers are connected to the same battery, each controller might be configured with a Battery Current Max Regen of -10A. The exact distribution can vary, but the total regenerative current returned to the battery should remain within the limits of the battery system.

Setting Battery Current Max Regen too high can result in:

• BMS charging overcurrent faults
• Battery overheating
• Reduced battery lifespan
• Overvoltage faults
• Damage to the battery in severe cases

Example

A system may be configured in VESC Tool with:

• Motor Current Max Brake: -120A
• Battery Current Max Regen: -20A

In this example, the controller can apply up to 120A of braking current through the motor while limiting the regenerative current returned to the battery to 20A.

⚠️ Regenerative braking is also limited by battery voltage, battery state of charge, and the configured Battery Voltage Regen Cut-Off Start and Battery Voltage Regen Cut-Off End settings. As the battery approaches full charge, regenerative braking may be reduced or disabled to prevent overvoltage.

In simple terms: Battery Current Max Regen determines the maximum charging current that can be returned to the battery during regenerative braking.