Voltage protection

The controller trips a fault when the battery voltage goes above or below four thresholds. Two use the filtered voltage and react to sustained conditions. Two use single measurements and react to fast spikes and dips. This page explains how the four thresholds work and how to set them for your battery.

WARNING

These faults protect the controller and the battery. This controller can regenerate into the battery, and regen can raise the battery voltage quickly, especially if the battery disconnects itself while the motor is above base speed. Set the over voltage thresholds within the controller input rating, and do not set the under voltage thresholds below the safe lower limit of your battery.

Prerequisites

Rated system voltage is set to the nominal voltage of your battery. See Rated limits.
You know the battery's fully charged voltage, fully discharged voltage and safe operating limits from the battery datasheet.
You know the input voltage rating of your controller. See Product specifications.

How it works

All four thresholds are a percentage of Rated system voltage.

Fault	Threshold	Trips when
Controller over voltage (`Faults` bit 0)	`Slow over voltage threshold`	The filtered battery voltage stays above the threshold for more than 1 second.
Controller under voltage (`Faults` bit 6)	`Slow under voltage threshold`	The filtered battery voltage stays below the threshold for more than 1 second.
Instantaneous controller over voltage (`Faults` bit 12)	`Fast over voltage threshold`	One battery voltage measurement is above the threshold while the bridge is enabled.
Instantaneous under voltage (`Faults` bit 15)	`Fast under voltage threshold`	One battery voltage measurement is below the threshold while the bridge is enabled.

Voltage protection faults

All four faults disable the motor phase bridge. The slow faults clear on their own when the voltage returns within the threshold for more than 1 second. The fast faults need a reboot or a fault reset command.

These faults cannot be disabled. You can only move the thresholds.

For example, with Rated system voltage at 48 V and Slow over voltage threshold at 110%, the Controller over voltage fault trips if the filtered voltage stays above 52.8 V.

Configure voltage protection

Set Slow over voltage threshold above the highest battery voltage you expect in normal operation, including during regen. It can be set up to the limit of the controller input rating.
Set Fast over voltage threshold above the battery's upper voltage limit, and above Slow over voltage threshold. It can be set up to the limit of the controller input rating.
Set Slow under voltage threshold to the voltage of your fully discharged battery. For example, if your fully discharged battery is at 85% of its nominal voltage, set Slow under voltage threshold to 85%.
Set Fast under voltage threshold to the safe lower limit of your battery, below Slow under voltage threshold.
Save the parameters to flash.

Verify

Run the system through its normal range: full charge, heavy acceleration, regen braking and low charge.
Check that none of the four faults trips in normal operation.
If a fault trips, check the cause before moving a threshold. See the troubleshooting below.

Troubleshooting

Over voltage faults during regen braking

The battery or power supply may not accept the regen current, or may disconnect itself because of a sensitive charge protection threshold. This can cause an instantaneous voltage spike, especially when the motor is above its base speed. Make sure the battery is adequately sized for the regen current, and check its charge protection settings. See also Rated limits for the regen battery current limit.

Under voltage faults during acceleration

The battery or power supply may not supply the current, or may disconnect itself because of sensitive output short-circuit protection when the bridge is enabled with a high current command. Make sure the battery is adequately sized, and that the battery terminals are secure.

For each fault's full description, see Faults and warnings.

Parameters

Parameter	Address	Units	Description
`Rated system voltage`	70	V	Nominal battery voltage. The voltage thresholds are a percentage of this value.
`Fast over voltage threshold`	147	% of rated system voltage	Instantaneous over voltage trip threshold.
`Fast under voltage threshold`	148	% of rated system voltage	Instantaneous under voltage trip threshold.
`Slow over voltage threshold`	149	% of rated system voltage	Filtered over voltage trip threshold.
`Slow under voltage threshold`	150	% of rated system voltage	Filtered under voltage trip threshold.

Parameters used on this page