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Lynx Smart BMS

8. Troubleshooting and Support

In this section:

Consult this chapter in case of unexpected behaviour or if you suspect a product fault.

The correct troubleshooting and support process is to first consult the common issues as described in this chapter and the Appendix section 10.1. LED indications, warnings, alarm and error codes.

Should this fail to resolve the issue, contact the point of purchase for technical support. If the point of purchase is unknown, refer to the Victron Energy Support webpage.

8.1. How to recover from OFF mode when no charge voltage was detected

This chapter explains how to turn on the BMS (thereby activating the system again) after the BMS has switched to OFF mode when no charge voltage has been detected for 5 minutes after a low cell voltage event or a low SoC shutdown.


If, after a low cell voltage or low SoC event, the BMS does not detect a charge voltage within 5 minutes, the BMS will enter OFF mode. In OFF mode, the ATC and ATD contacts are open and all interfaces except Bluetooth are turned off to conserve energy. When the ATC and ATD contacts open, all chargers and loads turn off. If, at a later stage, the chargers in the system are powered by the grid or a generator, they still will remain off, because the BMS is not generating the ATC signal.

There are two ways to make the BMS leave the OFF state so that the system will power up:

  • Connect an external charger to the system. The BMS will resume normal operation and close the contactor, when it detects a charge voltage on the system side of the BMS.

  • Use the Remote on/off switch or the soft switch in the VictronConnect app as described in Force the BMS out of OFF mode down below.

Force the BMS out of OFF mode:

To force the BMS to out of OFF mode, switch the BMS Remote on/off switch or the soft switch in the VictronConnect app off for 5 seconds and then switch it back on or unplug the 11-pin multi connector from its socket and reinsert it after 5 seconds.

The BMS will activate and close its contactor so that the battery is again connected to the system, even though the battery voltage might be too low. The BMS will close the ATC and ATD contacts, providing that the battery allows this. However, in case of an empty battery, the ATD contact will stay open and only the ATC contact will close.

As soon as the ATC contact is closed, the chargers in the system will reactivate and start to charge the battery.

Once the battery is sufficiently charged, the ATD contact will close and the loads will reactivate.


Note that if there is no sufficient charge voltage (check the BMS operating mode chapter for charge voltages) detected within 5 minutes, the BMS will enter OFF mode again. In that case, you must restart the Force the BMS out of OFF mode procedure. Make sure beforehand that a sufficient charge source is available.

Please also note that the above procedure is not required when DVCC controlled chargers are present in the system. They will charge for a few minutes or MPPT chargers will stay on regardless of whether the GX device and/or ATC status is off.

8.2. Lynx Smart BMS does not power up

This can be caused by one of the following reasons:

No battery supply

No LEDs are illuminated on the Lynx Smart BMS. Check the battery supply voltage into the Lynx Smart BMS. Check cables and fuses on the battery side. It could also be that the Lynx Smart BMS is in OFF mode. For more info on that see paragraph Powering up [29].

Reverse battery supply

Check the polarity of the supply voltage into the Lynx Smart BMS. If reverse polarity, correct polarity mistake. Unit should now power up.

No charge voltage detected for 5 minutes after a low cell voltage, low SoC or low temperature event

Make sure that a charger is connected and switched on. Ensure that the battery temperature is above the set threshold (default 5°C, adjustable in battery).

Remote on/off switched off or wire loop missing

The Remote on/off switch must be turned on or a wire loop must be inserted between pin 10 and pin 11 of the multi connector. Check that the multi connector is correctly seated.

Soft Switch turned off in VictronConnect App

Switch the system to ON mode using the soft switch in the VictronConnect app.

System in Standby mode

Switch the system to ON mode using the soft switch in the VictronConnect app or a connected GX device.

Battery voltage issues

The Lynx Smart BMS, on first install, will auto detect the battery voltage and set to either 12V, 24V or 48V. Each set voltage has a specific battery voltage range (threshold). If the Lynx Smart BMS measures a voltage that is outside this threshold, one of these alarms will be generated:

  • Probably wrong system voltage - red LED flashing 7 times every 4 seconds.

  • Battery voltage not allowed - red LED flashing 14 times every 4 seconds.

To fix, check the battery settings or check the battery voltage.

This table indicates the voltage thresholds for each system voltage:

System voltage

Voltage threshold


9V - 15V


16V - 30V


32V - 60V

Pre-charge errors

There are two specific errors that can be generated during the pre-charge process:

  • Pre-charge high current – red LED flashing 6 times every 4 seconds. The pre-charged energy or current has been exceeded.

  • Pre-charge timeout – red LED flashing 5 times every 4 seconds. It has taken too long for the pre-charge process to complete.

Pre-charge faults are mostly caused by:

  • A short circuit on the load output – potentially caused by a malfunctioning load or if there is a wiring issue like a short circuit.

  • Loads with a too high capacitance or too low resistance (less than 20 Ohm) have been connected to the load output.

To fix these errors, turn off or remove some loads or chargers and rule out wiring problems or shorts.

Internal error

Contact your Victron supplier if one of the following errors are occurring:

  • Internal supply error - Red LED flashing 12 times every 4 seconds

  • Initialization error - Red LED flashing 9 times every 4 seconds

  • Contactor failure - Red LED flashing 10 times every 4 seconds

  • Hardware error - GX device alarm calibration lost - GX device alarm

8.3. Lynx Smart BMS operational issues

High discharge current

A high current alarm is given when the current is more than 600A (1200A) for more than 5 minutes. The red LED flashes 8 times every 4 seconds. Reduce the loads connected to the Lynx Smart BMS so that the current through the Lynx Smart BMS will be below 500A (1000A).

High charge current

A high current alarm is issued when the current exceeds 600A (1200A) for more than 5 minutes. The red LED flashes 8 times every 4 seconds. Turn chargers off so that the current through the Lynx Smart BMS will be below 500A (1000A).

Contactor (relay) issues

The Lynx Smart BMS is equipped with 3 guards to protect the contactor.

  • Over current protection: an alarm is generated when the current exceeds 600A (1200A) for 5 minutes.

  • Contactor voltage monitoring: an alarm is generated when the voltage over the contactor is higher than 0.5V. A high voltage indicates high resistance and high power dissipation, indicating a bad contactor.

  • Electrical/mechanical protection: there are 2 thermal switches mounted on the busbar. The contactor opens and an alarm is generated when the temperature of the busbars becomes higher than 130°C.

High BMS temperature

Check ambient temperature and check if the two built-in fans are running. Reduce the ambient temperature.

Settings invalid

Settings data is corrupt. Reset to factory defaults.

8.4. BMS issues

8.4.1. The BMS frequently disables the battery charger

A well-balanced battery does not disable the charger, even when the batteries are fully charged. But when the BMS frequently disables the charger, this is an indication of cell imbalance.

In case of moderate or large cell imbalance it is an expected behaviour that the BMS frequently disables the battery charger. This is the mechanism behind this behaviour:

As soon as one cell reaches 3.75V, the BMS disables the charger due to high cell voltage. Whilst the charger is disabled, the cell balancing process still continues, moving energy from the highest cell into adjacent cells. The highest cell voltage drops and as soon as it falls below 3.6V, the charger is activated again. This cycling typically takes between one and three minutes. The voltage of the highest cell will rise again quickly (this can be in a matter of seconds), after which the charger will be disabled again and so forth. This does not indicate a problem with the battery or the cells and will continue with this behaviour until all cells are fully charged and balanced. This process might take several hours, depending on the level of imbalance. In case of serious imbalance this process can take up to 12 hours. Balancing will continue throughout this process and balancing even takes place when the charger is disabled. The continued enabling and disabling of the charger can appear strange, but rest assured that there is no problem. The BMS is merely protecting the cells from over voltage.

8.4.2. The BMS is prematurely turning loads off

This could be because of a cell imbalance.

If a cell voltage falls below the "Allowed-to-Discharge cell voltage" setting in the battery (default 2.8V), the BMS will turn the loads off.

Check the cell voltages of all batteries that are connected to the BMS using the VictronConnect app. Also check if all batteries have the same "Allowed-to-Discharge cell voltage" settings.

Once the loads have been turned off due to low cell voltage, the cell voltage of all cells needs to be 3.2V or higher before the BMS will turn the loads back on.

8.4.3. The pre-alarm setting is missing in VictronConnect

Pre-alarm is only available if the battery supports it. The current battery models all support it, but older batteries do not have the hardware required for the pre-alarm feature.

8.4.4. BMS is displaying alarm while all cell voltages are within range

A possible cause is a loose or damaged BMS cable or connector. Check all BMS cables and their connections.

Also consider that once there has been a cell under voltage alarm, the cell voltage of all cells need to be increased to 3.2V before the battery clears the under voltage alarm.

A way to rule out if a fault is originating from a faulty BMS or from a faulty battery is to check the BMS using one of the following BMS test procedures:

Single battery and BMS check:

  • Disconnect both BMS cables from the BMS.

  • Connect a single BMS extension cable between both BMS cable connectors. The BMS cable should be connected in a loop, as in below diagram. The loop tricks the BMS in thinking that there is a battery connected without any alarms.

  • If the alarm is still active after the loop has been placed, the BMS is faulty.

  • If the BMS cleared the alarm after the loop has been placed, the battery is faulty and not the BMS.


Testing a Lynx Smart BMS by connecting a single BMS extension cable to both BMS cable connections

Multiple batteries and BMS check:

  • Bypass one of the batteries by disconnecting both its BMS cables.

  • Connect the BMS cables of the neighbouring batteries (or battery and BMS) to each other, effectively bypassing the battery.

  • Check if the BMS has cleared its alarm.

  • If the alarm has not been cleared, repeat this for the next battery.

  • If the alarm is still active after all batteries have been bypassed, the BMS is faulty.

  • If the BMS cleared its alarm when a particular battery was bypassed, that particular battery is faulty.


Eliminating a BMS error by bypassing a suspect battery

8.4.5. How to test if the BMS is functional

To test if the BMS is functional, disconnect one of the battery BMS cables and see if the BMS will go into alarm mode.


Check BMS functionality by deliberately loosening a BMS cable

8.4.6. System in OFF mode

This is indicated by the status LED off and the Bluetooth LED flashing every 3 seconds.

The Lynx Smart BMS goes into OFF mode once a low cell voltage event occurred and no charge voltage has been detected for 5 minutes to conserve as much power as possible. Bluetooth is still active, but other non-essential interfaces are turned off, including the power to the Lynx Distributor(s).

Check the cell voltages of the connected batteries and if they are low, charge the batteries. As soon as the Lynx Smart BMS sees a charge voltage, it will automatically reactivate and close its contactor to allow for battery charging.

8.4.7. ATC/ATD is missing

Error #36 (ATC/ATD error) occurs when discharge current > 1.5A while ATD is disabled or when charge current > 1A while ATC is disabled.

This can be caused by loads or chargers that are not controlled by ATC/ATD.

Make sure all loads and chargers are controlled by ATC/ATD (if not controlled by DVCC).

8.5. Battery monitor issues

8.5.1. Incomplete current reading

The negatives of all loads and charge sources in the system must be connected to the system minus side of the shunt, which is the right side of the BMS in normal position.

If the negative terminal of a load or charging source is connected directly to the battery negative terminal or the “battery negative” side of the shunt, its current will not flow through the battery monitor. It will therefore not be taken into account and results in a wrong SoC reading.

8.5.2. Incorrect state of charge reading

An incorrect state of charge can be caused by a variety of reasons.

Incorrect battery settings

The following parameter(s) will have an effect on the state of charge calculations if they have been set up incorrectly:

  • Battery capacity

Double check via VictronConnect app that the Battery capacity settings of the Lynx Smart BMS is correct.

Incorrect state of charge due to a synchronisation issue:

The synchronisation process is automatic and is performed each time the battery is fully charged. The battery monitor determines that the battery is fully charged when all 3 "charged" conditions have been met. The "charged" conditions are:

  • Charged voltage (Voltage)

  • Tail current (% of battery capacity)

  • Charge detection time (minutes)

Practical example (default battery monitor settings and a 12.8V 200Ah lithium battery) for the conditions that must be met before synchronisation takes place:

  • The battery voltage has to be above 14.0V.

  • The charge current has to be less than 0.04 x battery capacity (Ah). For a 200Ah battery this is 0.04 x 200 = 8A

  • Both above conditions have to be stable for 3 minutes

If the battery is not fully charged or if the automatic synchronisation does not happen, the state of charge value will start to drift and will eventually not represent the actual state of charge of the battery.

The SoC can also be synchronised and set manually via the VictronConnect app (requires VictronConnect v5.70 or later).

8.5.3. State of charge does not increase/decrease fast enough or too fast when charging/discharging.

This can happen when the battery monitor thinks the battery is bigger or smaller than in reality. Check if the battery capacity has been set correctly.

8.5.4. Synchronisation issues

If the battery monitor does not synchronise automatically, one possibility could be that the battery never reaches a fully charged state. Fully charge the battery and see if the state of charge eventually indicates 100%.

Another possibility is that the Charged voltage setting should be lowered and/or the Tail current setting should be increased.

It is also possible that the battery monitor synchronises too early. This can happen in solar systems or in systems that have fluctuating charge currents. If this is the case, try to decrease the Charged voltage, Tail Current and Charged detection time settings slightly.

8.6. VictronConnect issues

Interrupted firmware update

This is recoverable. Just try to update the firmware again.

8.7. GX device issues

This chapter only describes the most common issues. If this chapter does not solve your issue, consult the manual of the GX device.

Incorrect CAN-bus profile selected

Check that VE.Can is set to use the correct CAN-bus profile. On your GX device navigate to Settings/Services/VE.Can port and check if it is set to "VE.Can & Lynx Ion BMS (250kbit/s)".

Also make sure that the Lynx Smart BMS is connected to the VE.Can port of your GX device and not the BMS-Can port (e. g. on a Cerbo GX).

RJ45 terminator or cable issue

VE.Can devices connect in "daisy chain" to each other and a RJ45 terminator needs to be used with the first and last device in the chain.

When connecting VE.Can devices, always use "manufactured" RJ45 UTP cables. Do not manufacture these cables yourself. Many communication and other seemingly unrelated product issues are caused by faulty home made cables.