1. General description
The VE.Bus BMS V2 is a battery management system (BMS) for Victron Energy Lithium Battery Smart batteries available with a nominal voltage of 12.8V or 25.6V in various capacities. This is the safest of the mainstream lithium battery types. They can be connected in series, parallel and series/parallel so that a battery bank can be built for system voltages of 12V, 24V or 48V. Up to four 12.8V batteries or two 25.6V batteries can be connected in series. A total of 20 batteries can be connected, resulting in energy storage of up to 84kWh in a 12V system or up to 102kWh in a 24V and 48V system.
Protects each individual cell of a Victron Lithium Battery Smart (LiFePO₄) battery
Each individual cell of a LiFePO₄ battery must be protected against under- and overvoltage, as well as low and high temperature. This is exactly what the VE.Bus BMS V2 does in combination with the battery's BTV module, which provides appropriate signals to the BMS.
The Victron Lithium Battery 12.8V & 25.6V Smart have integrated Balancing, Temperature and Voltage control (acronym: BTV) and connect to the VE.Bus BMS V2 with two M8 circular connector cord sets. The BTVs of several batteries can be daisy chained. Please see our Lithium Battery Smart product page for details.
Depending on the signals from the battery, the BMS will:
Generate a pre-alarm signal to warn of an imminent cell undervoltage.
Shut down or disconnect loads in case of cell undervoltage.
Turn off the inverter of VE.Bus inverter/chargers in case of cell undervoltage.
Reduce the charge current in case of cell overvoltage or overtemperature of VE.Bus inverter/chargers or VE.Bus inverters.
Shut down or disconnect battery chargers in case of cell overvoltage or overtemperature.
Pre-alarm
The pre-alarm output is normally free floating and becomes high in case of imminent cell undervoltage. It is set by default at 3.1V per cell and is adjustable on the battery between 2.85V and 3.15V per cell. The minimum delay between pre-alarm and load disconnect is 30 seconds. Note that the pre-alarm does not generate a notification on the GX device and therefore not on VRM either.
Load disconnect
The Load disconnect output is normally high and becomes free floating in case of cell undervoltage. The Load disconnect output can be used to control:
The remote on/off terminal of a load.
The remote on/off terminal of an electronic load switch like a BatteryProtect (preferred low power consumption solution).
Charge disconnect
The Charge disconnect output is normally high and becomes free floating in case of cell over voltage or over temperature. The Charge disconnect output can be used to control:
The remote on/off terminal of a charger, like an AC charger, DC-DC charger or solar charger.
A Cyrix-Li-Charge relay.
A Cyrix-Li-ct Battery Combiner.
LED indicators
The BMS has the following LED indications:
Status LED (blue): Lights once every 10 seconds when the Multi is switched on to indicate BMS info frames are being sent.
When the Multi is off, either due to a low cell/remote off or just switched off by means off the front panel switch, the BMS goes into low power mode but continues to send BMS info frames (with a slightly longer interval between them). In this mode the BMS status led does not light up to conserve energy. If the BMS is stuck in the bootloader, the status LED will flash rapidly. This can happen, for example, after an interrupted firmware update (to fix this, restart the update on VictronConnect or via VRM).
Cell voltage above 4V LED (red): Lights when the Charge disconnect output is low because of cell overvoltage or overtemperature.
Cell voltage above 2.8V LED (blue): Lights when the Load disconnect output is high and the battery cell voltages are above 2.8V.
Connectivity and communication with GX device
On/off/charger-only control of VE.Bus products via a GX device.
GX DVCC control of solar chargers. There is no need to install an BatteryProtect or Cyrix-Li-Charge to control solar chargers via the BMS like the VE.Bus BMS V1 does.
Has separate power input and output connections for GX devices
The GX-Pow output supplies GX power from either the battery or from the Aux-In input, whichever voltage is higher.
An AC-DC adapter (not included) or other power supply connected to the Aux-In input will ensure that the GX device is powered as long as that Aux power is available, even if the battery is low, for example, due to an error the battery is in under voltage and the inverter/charger is switched off. This allows the system to be diagnosed remotely (assuming the Internet is still available), even when (almost) everything else is turned off. See the Technical specifications for the required power rating of an AC-DC adapter.
True remote on/off terminal
The VE.Bus BMS V2 needs to remain connected to the battery positive in order to be able to keep the Multi in low power mode even when AC input on the Multi is available (Multi will stop inverting/charging, close the transfer switch and indicate a low battery error on the status LEDs). In comparison, disconnecting the battery positive of the VE.Bus BMS V1 only really turns the Multi off when no AC input is available.