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smallBMS NG

2. Introduction

In this section:

2.1. General description

The smallBMS NG with pre-alarm is an all-in-one Battery Management System (BMS) for Victron Lithium NG batteries (not to be confused with the lithium smart batteries without NG). These batteries are Lithium Iron Phosphate (LiFePO4) batteries and are available in 12.8V, 25.6V and 51.2V in various capacities. They can be connected in series, parallel, or a combination of both to create battery banks for system voltages of 12V, 24V, or 48V. A maximum of 50 batteries can be used when configuring a bank with 12V or 24V batteries, while up to 25 batteries can be used with 48V batteries. This allows for a maximum energy storage capacity of 192 kWh with 12V batteries, up to 384 kWh with 24V batteries, and 128 kWh with 48V batteries. For comprehensive details about these batteries, visit the Victron Lithium NG battery product page.

The smallBMS NG is a simple and cost-effective alternative to the VE.Bus BMS NG, but lacks a VE.Bus interface and is therefore not suitable for use with VE.Bus MultiPlus and Quattro inverter/chargers.

2.2. Features and functionality

  • Bluetooth Smart

    • The smallBMS NG has built-in Bluetooth Smart, enabling wireless configuration, monitoring, and firmware updates via Apple and Android smartphones, tablets, or other compatible devices. Various parameters can be adjusted using the VictronConnect App.

    • This also includes Instant Readout, allowing key BMS and battery data - SoC, battery temperature, warnings, and alarms - to be displayed on the VictronConnect device list without needing to connect to the product.

  • Load Disconnect output

    • Controls the remote on/off input of a BatteryProtect, Inverters, DC-DC converter, or other loads with remote on/off functionality.

    • The output is normally high, becomes free-floating when cell undervoltage is imminent. Maximum output current: 1A (not short-circuit protected).

      Note that a non-inverting or inverting on/off cable may be required (see Appendix A).

  • Charge disconnect output

    • Controls the remote on/off port of chargers such as the Smart Charger IP43, a Cyrix-Li-Charge relay, a Cyrix-Li-ct Battery Combiner or a BatteryProtect. Note that the Charge disconnect output is not suitable to power an inductive load such as a relay coil.

    • The output is normally high, becomes free-floating in case of imminent cell overvoltage or overtemperature. Maximum output current: 500mA (not short-circuit protected).

  • Remote on/off terminal

    • Allows remote control of the Load and Charge Disconnect outputs. When off, both outputs become free-floating, turning off connected loads and chargers.

    • Consists of two terminals: Remote L and Remote H.

    • Can be operated using:

      • A switch or relay contact between L and H.

      • H switched to battery plus or L switched to battery minus.

      Important

      An on/off switch or the default wire loop must be installed for correct operation.

  • Pre-alarm output

    • Triggers a visible or audible warning when battery voltage is low, activating at least 30 seconds before the Load Disconnect output is disabled due to cell undervoltage.

    • Can drive a relay, LED, or buzzer. Maximum output current: 1A (not short-circuit protected).

    • The output is normally free-floating, becomes high in case of imminent cell undervoltage.

    • The pre-alarm level can be adjusted via VictronConnect.

  • Configurable discharge floor

    • Defines the minimum SoC to prevent excessive discharge and ensure enough energy remains for self-discharge after a low SoC shutdown.

    • A low SoC warning level can be set, triggering a warning in VictronConnect that the discharge floor is about to be reached. The pre-alarm output is activated as soon as the warning level is reached. The value should be set high enough to leave enough time to recharge the battery to prevent a low SoC shutdown.

    • A low SoC alarm is triggered when the discharge floor is reached, and the BMS immediately deactivates the ATD output, effectively shutting off any loads it controls.

  • LED indicators

    • Blue Bluetooth Status LED:

      • Blinks when no connection to VictronConnect. Lit solid when connected.

    • Red Error LED:

      • Solid when an error occurs (details available in VictronConnect). Blinks in case of a warning (details available in VictronConnect).

2.3. What's in the box

smallBMS NG with removable 7-pin terminal block for easy wiring

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