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/charger units, as it does not have a VE.Bus interface. The smallBMS is designed for use with Victron Smart LiFePo4 batteries with M8 round connectors.
The smallBMS has two outputs, similar to the VE.Bus BMS.

Load disconnect output
The load output is normally high and becomes free floating when the cell voltage is below the setpoint (default 2.8 V/cell, adjustable
at 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 BatteryProtect, an inverter or DC-DC converter, or other loads.
(A non-inverting or inverting cable for switching on/off may be necessary; please refer to the manual for details.)

Charge disconnect output
The charger output is normally high and becomes free floating in the event of an 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 coupler.

Pre-alarm output
The pre-alarm output is normally free floating and goes high when the cell voltage is approaching the low voltage limit (default 3.1 V/cell, adjustable at
the battery between 2.85 V and 3.15 V per cell). Maximum current: 1 A (not short-circuit protected).
The minimum delay between the pre-alarm and load disconnection is 30 seconds.

"Charge disconnect" output
The "Charger" output is normally high and becomes "free floating" when a cell overvoltage or over-
temperature 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 coupler.

System on/off input
The system on/off input controls both outputs. In the switched-off state, both outputs are free floating, so that loads and
chargers are switched off.
The "System on/off" input has two connections: Remote L and Remote H.
A remote on/off switch or relay contact can be connected between L and H.
Alternatively, connection H can be connected to a battery positive terminal or L to a battery negative terminal.

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

LED displays

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