The BMS reports a fault
Level faults
These are faults that report a condition outside limits.
For all level faults (other than the Interlock Fault), the fault condition must last longer than the Fault Delay before the BMS goes into a Fault State.
Level faults are cleared once the condition returns to normal; there is no other way to clear a level fault other than fixing the condition that resulted in a fault.
Even if a level fault is cleared, the BMS remains in the Fault State; to exit the Fault State, normally BMS operation must be restored manually, by either cycling the power off and on, or by issuing a command to clear the Fault State, either through the CAN bus or through the RS232 terminal.
The following messages may appear in the Status / System screen as the "Most recent fault" or "Present fault".
They remain in the "Most recent fault" line until replaced by another fault, or the Fault State is cleared manually.
Driving off while plugged in
Interlock is tripped
Communication fault with a bank or cell
Charge over-current
This fault means that the BMS sees excessive current into the battery, such as:
- Current that exceeds the Peak Charge Current setting for longer than a short time
- Current that exceeds the Continuous Charge Current setting for too long
- Current that exceeds the CCL (Charge Current Limit)
- Any current at all when the BMS says that no current is allowed (the BMS's HLIM signal is active)
To troubleshoot this, first note if the BMS is enabling charging at the time of the fault.
- Go to the Log (Home / Log) and look for a record with a Charging Over-current fault.
- In that record, see if the HLIM was active at the time ("Cannot charge") or inactive ("Charging is OK")
- Based on that, read the appropriate sub-section, below
"Charging is OK"
The BMS issued a "Charging over-current" fault while its HLIM was inactive ("Charging is OK").
The likely cause is that the BMS doesn't see the charging current, and sees a huge value instead. That can be due to:
- A miswired current sensor
- The BMS is not properly configured for the sensor
To solve that, see the sensor troubleshooting section on measured data.
On the other side, if the BMS does see the correct current, then the problem may be that the charging current limits are configured too low.
- Go to the current limits settings (Home / Set-up / Charge limits / Current / Peak current; and Home / Set-up / Charge limits / Current / Continuous current)
- Check that the values entered are appropriate for the cells used
Finally, it is possible that the BMS is configured properly, and the problem is that the system really is charging the battery at too high a current, and the BMS is correctly reporting a charging over-current. If that is the case, you need to fix the system so that it is unable to produce so much charging current.
"Cannot charge"
The BMS issued a "Charging over-current" fault while its HLIM was active ("Cannot charge"). This is the most common instance of a charge over-current fault.
It is usually due to one of three causes:
- The system is not wired in a way that lets the BMS shut off the charger
- The BMS sees current into the battery when there isn't any
- The BMS sets a fault immediately as the current reading is still decaying on its way to 0
BMS cannot shut off charger
The system MUST be wired so that the BMS directly controls the charging source (such as a charger or regen braking). When the BMS's HLIM line is active, any device that could charge the battery MUST be prevented from doing so. For example, when using a charger, the HLIM line should drive a relay that interrupts the AC to the charger input.
If that is not the case:
Charging continues even though a cell is full, which is a FIRE DANGER
- Balancing cannot occur
- The BMS goes in the Fault State
The solution is to wire the system so that the BMS can disable any device that could charge the battery.
BMS sees charging current when it's 0
If the BMS sees current into the battery even though there isn't any, when charging is disabled it will issue a fault.
This happens if the BMS is not configured properly for the current sensor:
- The offset is not calibrated
- The offset was calibrated at room temperature, but the sensor has since drifted
- The direction of the current sensor is wrong
- The BMS is configured to look at the wrong current sensor
The solution is to make sure that the BMS sees 0 current when there is no battery current. With no current in or out of the battery, look at value for current reported in the System Status screen (Home / Status / System).
- If the BMS is powered by VS (which it should be if the product is plugged in the AC power), the Source Current value should be as close as possible to 0 A.
- If the BMS is powered by VL, the Load Current value should be as close as possible to 0 A.
If not, calibrate the offset of the current sensor, until the reading is 0:
- Select Home / Set-up / Current sense / Load sensor (or Source sensor, as appropriate) / Current Sensor / Monitor
- Note the value reported for that sensor (typically, CTRL for an in-line current sensor, EXT for a cable mounted sensor)
- Press ESC to return to the previous menu
- Select Offset
- Enter the value you noted before
- Check the Status Screen again and confirm the reading is close to 0 A
BMS sets fault immediately
In order to handle chargers whose output is not filtered (the current is not flat DC, but a fully rectified sine wave at twice the line frequency), the BMS uses heavy filtering of the current. As a result, when the BMS shuts off charging, even if the current ends suddenly, the reported current takes a few seconds to decay to 0. During that time, there is a fault condition (the BMS says that there can't be any charging current, yet current seen by the BMS is non-zero). However, the BMS doesn't issue a fault yet, because it first waits for the Fault Delay. As long as the reading of the current decays to 0 before the Fault Delay expires, the BMS does not issue a fault. If, however, the user configured the BMS with a very short Fault Delay, or even a 0 s Fault Delay, there is not enough time for the reading of battery current to settle to 0, and the BMS issues a fault.
The solution is to increase the Fault Delay (Home / Set-up / Fault / Fault delay).
Discharge over-current
Over-temperature fault
Under voltage
Over voltage
Transitory faults
These are faults that are detected just once during a test, and remain latched regardless of whether the conditions have returned to normal.
The following messages may appear in the Status / System screen as the "Most recent fault". They remain in the display until replaced by another fault.
No battery voltage
High voltage B- leak to chassis
High voltage B+ leak to chassis
Relay K1 is shorted
Contactor K2 is shorted
Contactor K3 is shorted
No precharge {Rev 0.91 was TxtK13Opn:
Open K2
Excessive precharge time
EEPROM stack overflow
Limits
The following messages may appear in the Status / System screen next to the CCL and DCL values, to indicate why the values are less than 100 %.
Pack voltage too low
Pack voltage too high
Cell voltage too low
Cell voltage too high
Temperature too high
Temperature too low