ACB BMS

# ETA3000 3S Active Cell Balancer

A compact 3-cell (3S) inductive active cell-balancing module designed using the ETA3000 active cell-balancing IC.


## Project Overview

This project was developed as part of an Electronics Systems task to design and develop a compact active cell-balancing module for a 3S battery system intended for drone applications.

In conventional passive cell balancing, excess energy from a higher-voltage cell is dissipated as heat through a balancing resistor. This results in energy loss and additional thermal stress.

The ETA3000-based design uses **inductive active cell balancing**, where energy is transferred between cells instead of simply being dissipated as heat.

The target balancing current for this design is **up to 1.2 A**.

---

## Specifications

| Parameter | Specification |

| ------------------------ | -------------------------- |

| Battery configuration | 3S |

| Number of cells | 3 |

| Balancing method | Inductive active balancing |

| Balancing IC | ETA3000 |

| Target balancing current | Up to 1.2 A |

| PCB design software | KiCad |

| PCB type | Custom 2-layer PCB |

| Main design objective | Compact form factor |

| Application | Drone battery system |

---

## Design Architecture

The three battery cells are connected to the active-balancing circuit through the cell input connections.

The ETA3000 controls the inductive energy-transfer process between the cells. When a voltage imbalance exists, energy can be transferred from a higher-voltage cell toward a lower-voltage cell.

Unlike passive balancing, the energy is not intentionally converted into heat through a large balancing resistor.

### Basic concept

 Higher-voltage cell

        │

        ▼

   ETA3000 Control

        │

        ▼

   Inductive Energy

      Transfer

        │

        ▼

 Lower-voltage cell

The actual switching and energy-transfer behaviour is determined by the ETA3000 architecture and its external components.

---

## Schematic


The schematic was designed according to the ETA3000 datasheet/application information and the requirements of the 3S battery configuration.

Important design considerations include:

* Correct cell connections

* ETA3000 power connections

* Inductive energy-transfer components

* Local bypass/decoupling capacitors

* Appropriate component voltage ratings

* High-current balancing paths

* Correct grounding and return paths

---

## PCB Layout


The PCB layout was designed with compactness as one of the primary objectives.

Since the intended application is a drone battery system, reducing PCB area and unnecessary wiring is important.

The layout therefore considers:

* Short high-current paths

* Compact placement of the balancing components

* Inductor placement

* Decoupling capacitor placement

* Practical routing

* Copper width for balancing-current paths

* Component accessibility

* Clearance between different electrical nodes

---

## Compact Layout Considerations

A major challenge of the project was fitting the complete balancing circuit into a small PCB area.

The placement was performed with the following priorities:

1. Keep the main energy-transfer paths short.

2. Keep relevant passive components close to the ETA3000.

3. Minimize unnecessary routing.

4. Maintain suitable electrical clearances.

5. Provide sufficiently wide copper for higher-current paths.

6. Keep the overall board compact.

The final PCB layout was then checked using KiCad's Design Rules Checker.

---

## Current Handling

The target balancing current is approximately:

**1.2 A**

PCB trace width cannot be selected only from the nominal current. The actual design should also consider:

* Copper thickness

* Trace width

* Trace length

* Allowable temperature rise

* PCB layer

* Ambient temperature

* Current duty cycle

The higher-current balancing paths were therefore given greater consideration during PCB routing than low-current signal connections.

### Trace-width calculation

The final trace width should be justified using a PCB trace-width calculation based on the actual copper thickness and acceptable temperature rise.

Note: The numerical trace-width value should be added here based on the actual PCB copper thickness and the calculation used for this design.

---

## ETA3000 Custom Footprint

The ETA3000 footprint was not available directly in the default KiCad library used during the project.

A custom KiCad footprint was therefore created/imported for the ETA3000 package.

The custom footprint is included in:

ETA3000D2I.pretty/

└── ETA3000D2I.kicad\_mod

The footprint dimensions should be verified against the manufacturer's package drawing before fabrication.

---

## Component Selection

Component selection was performed with consideration for:

* ETA3000 recommended operating conditions

* Voltage ratings

* Current capability

* Package size

* PCB availability

* Compact placement

* Suitable footprints

For future fabrication, components should be checked against their latest manufacturer datasheets before ordering.

---

## PCB Manufacturing Files

The Gerbers/ directory contains the generated manufacturing files for the PCB.

These files can be used to inspect or manufacture the PCB using a PCB fabrication service.

Typical manufacturing outputs include:

* Front copper

* Back copper

* Solder masks

* Silkscreens

* Board outline

* Drill files

---

## Repository Structure

ETA3000-3S-Active-Cell-Balancer/

│

├── ACB\_BMS.kicad\_pro

├── ACB\_BMS.kicad\_sch

├── ACB\_BMS.kicad\_pcb

│

├── ETA3000D2I.pretty/

│   └── ETA3000D2I.kicad\_mod

│

├── Images/

│   ├── schematic.png

│   ├── pcb\_layout.png

---

## Tools Used

* KiCad

* ETA3000 datasheet

* ETA3000 application/reference information

* PCB Design Rules Checker

* PCB trace-width calculations

---

## Project Status

**PCB design completed.**

The current repository contains the KiCad schematic, PCB layout, custom ETA3000 footprint and manufacturing outputs.

Further validation would include:

* PCB fabrication

* Component assembly

* Power-up testing

* Cell-voltage measurement

* Balancing-current measurement

* Thermal testing

* Verification of balancing behaviour under different cell-voltage conditions

---

## Learning Outcomes

This project involved practical work in:

* Reading an IC datasheet

* Understanding active cell balancing

* Inductive energy transfer

* Component selection

* Custom KiCad footprint handling

* Schematic design

* PCB placement

* High-current PCB routing

* PCB trace-width considerations

* Design Rule Checking

* Gerber generation

* Git/GitHub version control

---

## Author

**Shreyash Birdawade**

Electronics & Telecommunication Engineering

GitHub: [@SHREYASHSB21](https://github.com/SHREYASHSB21)