The smallBMS with pre-alarm is an all-in-one Battery Management System (BMS) for Victron Energy Lithium Battery Smart batteries. These batteries are Lithium Iron Phosphate (LiFePO4) batteries and are available in 12.8V or 25.6V in various capacities. 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. The maximum number of batteries in one system is 20, which results in a maximum energy storage of 84kWh in a 12V system and up to 102kWh in a 24V⁽¹⁾ and 48V⁽¹⁾ system.

The smallBMS is a simple and inexpensive alternative to the VE.Bus BMS, but does not have a VE.Bus interface and is therefore not suitable for use with VE.Bus MultiPlus and Quattro inverter/chargers.

Features

• Load disconnect output: Can be used to control the remote on/off input of a BatteryProtect, Inverters, DC-DC converter or other loads that have remote on/off port functionality. Due to its maximum output current of 1A, it can even control a high-current relay or a contactor. Note that a non inverting or inverting on/off cable may be required, please consult the manual.
• Pre-alarm output: The pre-alarm output can be used to issue a visible or audible warning when the battery voltage is low and will trip with a minimum delay of 30 seconds before the Load disconnect output is disabled due to cell undervoltage.
• Charge disconnect output: Can be used to control the remote on/off port of a charger, such as the Smart Charger IP43, a Cyrix-Li-Charge relay, a Cyrix-Li-ct Battery Combiner or a BatteryProtect. The output is normally high and becomes free floating in case of imminent low cell voltage or high/low temperature. Note that the Charge disconnect output is not suitable to power an inductive load such as a relay coil.
• Remote on/off terminal: Both the Load and Charge disconnect output can be controlled remotely via the remote on/off terminal. When off, both outputs will be free floating so that loads and chargers are turned off.
• LED indicators: The smallBMS has two LED indicators, a blue LED indicating that the Load disconnect output is still high and the cell voltage is above the threshold set in the battery, and a red LED indicating that the Charge disconnect output is low due to high/low cell temperature or high cell voltage.

When fully

1. To reduce required balancing time, we recommend using a little different batteries in series as possible for the application. 24V systems are best built using 24V batteries. And 48V systems are best built using two 24V batteries in series. While the alternative, four 12V batteries in series, will work, it will require more periodic balancing time.

Cyrix Combiners designed for use with the smallBMS and the VE.Bus BMS:

• Cyrix-Li-ct (120A or 230A) Is a battery combiner with a Li-ion adapted engage/disengage profile and a control terminal to connect to the Charge Disconnect of the BMS.
• Cyrix-Li-Charge (120A or 230A) Is a unidirectional combiner to insert in between a battery charger and the LFP battery. It will engage only when charge voltage from a battery charger is present on its charge-side terminal. A control terminal connects to the Charge Disconnect of the BMS.