smallBMS with pre-alarm

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 12.8 V or 25.6 V 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 12 V, 24 V or 48 V. The maximum number of batteries in one system is 20, which results in a maximum energy storage of 84 kWh in a 12 V system and up to 102 kWh in a
24 V1) and 48 V1)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 Phoenix 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

1) To reduce required balancing time, we recommend to use a little different batteries in series as possible for the application. 24 V systems are best built using 24 V batteries. And 48 V systems are best built using two 24 V batteries in series. While the alternative, four 12 V 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 ofthe 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 BM