SmallBMS for Smart LiFePO4 Batteries with M8

A simple and low-cost alternative to the VE.Bus BMS. The smallBMS can replace the VE.Bus BMS in several applications. It is however not suitable for use with VE.Bus MultiPlus and Quattro inverter/chargers: it has no VE.Bus interface.

The smallBMS is intended for use with Victron Smart LiFePo4 batteries with M8 circular connectors. The smallBMS has three outputs, similar to the VE.Bus BMS. Load Disconnect output The Load output is normally high and becomes free-floating in case of the cell under voltage (default 2,8V/cell, adjustable on the battery between 2,6V and 2,8V per cell). Maximum current: 1A. The Load output is not short-circuit protected.

The Load output can be used to control:

• A high current relay or contactor.
• The remote on/off the input of a Battery Protect, inverter or DC-DC converter, or other loads.

Pre-alarm output

The pre-alarm output is normally free-floating and becomes high in case of the imminent cell under voltage (default 3,1V/cell, adjustable on the battery between 2,85V and 3,15V per cell). Maximum current: 1A (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 in case of imminent cell overvoltage or over-temperature. Maximum current: 10mA. The Charger output is not suitable to power an inductive load such as a relay coil.

The Charger output can be used to control:

• The remote on/off of a charger
• A Cyrix-Li-Charge relay
• A Cyrix-Li-ct Battery Combiner

System on/off input

The system on/off input controls both outputs. When off, both outputs will be free floating so that loads and chargers are turned off. The System on/off consists of two terminals: Remote L and Remote H. A remote on/off switch or relay contact can be connected between L and H. Alternatively, terminal H can be switched to battery plus, or terminal L can be switched to battery minus.

Protects 12V, 24V and 48V systems

Operating voltage range: 8 to 70V DC.

LED indicators:

• Load ON (blue): Load output high (cell voltage >2.8V, adjustable on the battery).
• Temp or OVP (red): Charger output free floating (due to cell over temperature (>50°C), cell under temperature (<5 °C) or cell over voltage).