Lynx Smart BMS

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.

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.

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.

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:

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

Multiple batteries and BMS check:

Eliminating a BMS error by bypassing a suspect battery

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

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.

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).

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.

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:

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:

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

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).

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.

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.