The 4S 1.2A Active Battery Balancer Equalizer (V1.5) is designed to maintain balanced cell voltages in compatible 4-series lithium battery packs. Available at BDTronics Bangladesh, this compact active balancing module transfers energy from higher-voltage cells to lower-voltage cells, helping reduce voltage differences and improve battery pack efficiency.

Unlike conventional passive balancing circuits that dissipate excess energy as heat, this active balancer uses energy transfer to equalize cell voltages. Supporting compatible LiFePO4 (LFP) and lithium-ion NCM battery configurations, it features automatic balancing activation, up to 1.2A balancing current, a low standby current, and an LED status indicator.

Suitable for solar energy storage, inverter battery packs, UPS systems, backup power, and DIY lithium battery projects, this module helps maintain more consistent cell voltages. BDTronics recommends using the balancer alongside a compatible BMS protection board, as active balancing alone does not provide complete battery protection.

Features:

• 4S Active Battery Balancing: Designed for four series-connected lithium battery cells in a nominal 12V-class battery pack.

• Active Energy Transfer: Transfers energy between cells to reduce voltage imbalance with less energy dissipation than passive resistive balancing.

• LiFePO4 and NCM Compatibility: Intended for compatible lithium iron phosphate (LFP) and lithium-ion NCM cells, subject to the module's actual voltage limits.

• Maximum Balancing Current of 1.2A: Provides up to 1.2A balancing current under suitable voltage difference and operating conditions.

• Automatic Balancing: Starts balancing when the voltage difference between adjacent cells reaches approximately 0.1V.

• Automatic Stop Function: Stops balancing when the adjacent-cell voltage difference falls to approximately 0.03V or below.

• Typical Balancing Accuracy: Approximately 30mV, according to the supplied specifications.

• Low Standby Current: Specified static working current of approximately 0.01mA (10μA).

• LED Balance Indicator: Displays balancing activity and status according to the module's indicator behavior.

• Compact PCB Design: Suitable for installation inside compatible battery enclosures.

• 5-Pin Balance Connector: Connects to the four-cell series battery pack through the corresponding balance leads.

• BMS-Compatible Installation: Designed to operate alongside a separate, appropriately configured battery management system.

• Available at BDTronics: Suitable for lithium battery assembly and energy storage projects in Bangladesh.

Specifications:

• Product Name: 4S 1.2A Active Battery Balancer Equalizer

• Brand: Generic / China

• Product Type: Active lithium battery balancing module

• Battery Configuration: 4S

• Nominal Battery Class: 12V, depending on battery chemistry

• Compatible Battery Chemistry: LiFePO4 (LFP) and lithium-ion NCM, subject to voltage compatibility

• LTO Compatibility: Not compatible

• Specified Single-Cell Voltage Range: 3.0V–4.2V, as supplied; verify compatibility with the selected chemistry and exact module version

• Recommended Battery Capacity: Supplied information lists both 5–100Ah and a separate under-30Ah application description. Confirm the intended capacity range with the seller before purchasing.

• Typical Balancing Accuracy: Approximately 30mV

• Balancing Start Threshold: Approximately 0.1V difference between adjacent cells

• Balancing Stop Threshold: Approximately 0.03V difference or below

• Balancing Current at 0.1V Difference: Approximately 0.5A, according to supplied specifications

• Maximum Balancing Current: Up to 1.2A at a voltage difference of approximately 0.2V or greater, under suitable conditions

• Static Working Current: Approximately 0.01mA (10μA)

• Status Indicator: LED

• Balance Cable: 5-pin cable

• Wire Length: Approximately 30cm

• Wire Gauge: 22AWG

• Dimensions: Approximately 2.16 × 0.90 × 0.25 inches (54.9 × 22.9 × 6.4mm)

Applications:

• 12V-class LiFePO4 battery packs

• Compatible 4S lithium-ion NCM battery packs

• Solar energy storage systems

• Solar inverter battery banks

• UPS and backup power systems

• Off-grid energy storage

• DIY lithium battery pack assembly

• Portable power systems

• Battery voltage equalization projects

• Compatible low-voltage energy storage equipment

How Active Battery Balancing Works

Lithium battery cells connected in series may develop different voltage levels because of differences in capacity, internal resistance, temperature, aging, and charging history. When one cell reaches its voltage limit before the others, the usable capacity of the entire battery pack can be reduced.

An active balancer transfers energy from higher-voltage cells to lower-voltage cells instead of simply dissipating excess energy as heat. This helps reduce cell voltage differences and maintain more consistent operation across the battery pack.

The 4S 1.2A active balancer operates automatically according to the supplied voltage thresholds:

• Voltage Difference of 0.1V or More: Balancing begins when the activation conditions are met.

• Larger Voltage Differences: Balancing current can increase, reaching up to 1.2A under suitable operating conditions.

• Voltage Difference of Approximately 0.03V or Less: Balancing stops according to the specified cutoff threshold.

• Low Standby Consumption: The specified static current of approximately 10μA helps minimize energy consumption while idle.

Actual balancing current depends on the circuit design, cell voltages, operating conditions, and module specifications.

Wiring Instructions

The 4S balancer uses five connection points to monitor a four-cell series battery pack. Connect each lead to the corresponding battery node.

• B−: Connect to the negative terminal of Cell 1 and the overall battery pack negative.

• B1: Connect to the positive terminal of Cell 1.

• B2: Connect to the positive terminal of Cell 2.

• B3: Connect to the positive terminal of Cell 3.

• B4: Connect to the positive terminal of Cell 4 and the overall battery pack positive.

The connection points represent successive electrical nodes in the series battery pack. Follow the manufacturer's wiring diagram and connection sequence before installation. Do not assume wire colours or connector orientation indicate the correct pinout.

Balance Indicator Status

• LED ON: Active balancing is in progress, according to the supplied indicator description.

• LED OFF: The module may be in standby or sleep mode.

• LED Flashing: May indicate a cell voltage drop or circuit fault condition, as described in the supplied information. Verify the exact LED code against the module documentation.

Installation and Usage Guide

• Verify Battery Chemistry: Confirm that the module supports the specific LiFePO4 or NCM cells being used.

• Check Individual Cell Voltages: Measure all four cells and verify that their voltages are within the module's supported limits.

• Install a Compatible BMS: Use a properly rated BMS with suitable overcharge, over-discharge, overcurrent, short-circuit, and temperature protection.

• Connect the Balance Leads: Attach B−, B1, B2, B3, and B4 to the correct battery nodes using the manufacturer's required sequence.

• Check Wiring Before Power-Up: Use a multimeter to verify the voltage between adjacent balance leads and confirm the complete pinout.

• Secure the Module: Mount the PCB firmly inside a suitable enclosure, with adequate insulation and protection from conductive debris.

• Monitor Initial Operation: Check the LED indicator, individual cell voltages, and module temperature during initial balancing.

• Verify Long-Term Operation: Periodically inspect connections and confirm that cell voltages remain within the battery manufacturer's recommended limits.

Important Compatibility and Safety Notes

• This module is an active battery balancer, not a complete BMS. It does not replace required battery protection functions.

• The supplied specification lists a single-cell range of 3.0V–4.2V. This range may not cover the full operating range of every LiFePO4 cell. Confirm the exact module's supported cell voltage before use, especially with LiFePO4 batteries.

• The product information gives conflicting battery capacity guidance: one section recommends packs below 30Ah, while another lists 5–100Ah. Confirm the applicable capacity range for the exact module.

• The 1.2A rating is a maximum balancing current, not a guaranteed continuous current.

• Never connect the balance harness using guesswork. Incorrect wiring can damage the module, battery cells, or connected equipment.

• Disconnect power and follow safe battery assembly procedures before changing wiring.

• Use suitable fusing, insulation, and a correctly rated BMS for the complete battery system.

Package Includes:

• 1 × 4S Active Battery Balancer PCB

• 1 × 5-Pin Balance Cable

Why Buy from BDTronics?

BDTronics supplies electronic components, lithium battery accessories, power electronics, and embedded system components in Bangladesh. This 4S active battery balancer is designed for compatible lithium battery projects requiring automatic cell voltage equalization.

Before ordering from BDTronics, verify your battery chemistry, individual cell voltage range, battery capacity, and BMS configuration to ensure that the module is suitable for your application.

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