Victron Battery Management System smallBMS with Pre-alarm

A Simple and Cost-Effective Alternative to the VE.Bus BMS

The smallBMS can replace the VE.Bus BMS in several applications. However, it is not suitable for use with VE.Bus MultiPlus and Quattro inverter/chargers, as it lacks a VE.Bus interface. The smallBMS is designed for use with Victron Smart LiFePo4 batteries with M8 circular connectors.
The smallBMS has two outputs, similar to the VE.Bus BMS.

Load Disconnect Output
The load output is normally high and becomes floating if the cell voltage is too low (default 2.8 V/cell, adjustable
on the battery between 2.6 V and 2.8 V per cell). Maximum current: 1 A. The "Load" output is not short-circuit protected.
The "Load" output can be used to control the following functions:
A high-current relay or contactor
The remote on/off input of a BatteryProtect, inverter, or DC-DC converter, or other loads.
(A non-inverting or inverting cable for on/off switching may be necessary; please refer to the manual for this)

Charger Disconnect Output
The charger output is normally high and becomes floating in case of impending cell overvoltage or overtemperature.
Maximum current: 10 mA.
The "Charger" output is not suitable for driving an inductive load, such as a relay coil.
The "Charger" output can be used to control the following devices:

• Remote on/off switch of a charger.
• Cyrix-Li-Charge Relay.
• Cyrix-Li-ct Battery Combiner.

Pre-alarm Output
The pre-alarm output is normally floating and goes high when cell undervoltage is impending (default 3.1 V/cell, adjustable on
the battery between 2.85 V and 3.15 V per cell). Maximum current: 1 A (not short-circuit protected).
The minimum delay between pre-alarm and load disconnect is 30 seconds.

Charge Disconnect Output
The "Charger" output is normally HIGH and becomes "free floating" if a cell overvoltage or
overtemperature is imminent. Maximum current: 10 mA.

The "Charger" output is not suitable for driving an inductive load, such as a relay coil.
The "Charger" output can be used to control the following devices:

• Remote on/off switch of a charger
• Cyrix-Li-Charge Relay.
• Cyrix-Li-ct Battery Combiner.

System On/Off Input
The system on/off input controls both outputs. When switched off, both outputs are free-floating, so loads and
chargers are disconnected.
The "System on/off" input has two terminals: Remote L and Remote H.
A remote on/off switch or a relay contact can be connected between L and H.
Alternatively, terminal H can be connected to a battery positive pole or L to a battery negative pole.

Protects 12 V, 24 V, and 48 V Systems
Operating voltage range: 8 to 70 V DC
 

LED Indicators

• Load ON (blue): Load output high (cell voltage > 2.8 V, adjustable on the battery).
• Temp or OVP (red): The charger output is free-floating (due to cell overtemperature (>50°C), cell undertemperature (<5
  °C) or cell overvoltage).

Documents & Downloads

• smallBMS Datasheet
• Victron smallBMS Manual