Sodium (18Ah Cells) 4S 3P Busbars and Hardware

Creating a robust 4S3P battery pack with 18Ah sodium cells requires careful attention to design and hardware choices, especially for the busbars and connecting hardware. Let’s look into the specifics for this configuration:

1. Overview of a 4S3P Sodium Battery Pack

In a 4S3P configuration:

• 4S (four cells in series) increases voltage.
• 3P (three series strings in parallel) increases capacity.

Using 18Ah sodium-based cells:

• Total Voltage: 4 cells in series x Nominal Voltage per cell (dependent on sodium chemistry, often around 2.3-2.7V) = ~9.2V - 10.8V.
• Total Capacity: 3 parallel groups x 18Ah = 54Ah.

2. Choosing Busbars

Busbars are essential for efficient current distribution across cells. Here are some key considerations:

• Material: Copper is ideal for high conductivity and minimal resistance, although aluminum can also work if weight is a concern (note: aluminum busbars will need to be thicker to handle the same current).
• Thickness: For a 4S3P pack capable of delivering high currents, choose a thickness of 2-3mm for copper or slightly thicker for aluminum.
• Width and Length: Typically, a 10-15mm wide busbar is adequate for medium to high currents in a pack of this size. The busbars should span only the distance needed to connect each cell within a series or parallel configuration.

3. Necessary Hardware

Quality hardware is vital for ensuring stable electrical connections and longevity. Here’s what’s required:

• Bolts and Nuts: Stainless steel bolts are a good choice for corrosion resistance. Use appropriately sized bolts to create a solid connection without overstressing the cells’ terminals.
• Washers: Use both flat and spring washers to distribute pressure and prevent the bolts from loosening due to vibration.
• Insulation: Heat-resistant insulation is critical for safety, particularly around areas where busbars might come into contact with other parts of the battery pack.
• Thread-locking Compound: Applying a thread-locking compound can help secure bolts and prevent loosening over time from vibration or thermal expansion and contraction.

4. Busbar and Cell Connection Guide

1. Arrange Cells: Organize the cells into a 4S3P arrangement, ensuring the cells are properly aligned and easy to access for busbar installation.
2. Install Series Connections: Begin with the series connections. Secure each busbar across the positive terminal of one cell to the negative terminal of the next in each series string.
3. Parallel Connections: Once the series connections are complete, connect each of the 4S strings in parallel. Ensure that each connection is equally spaced and well-torqued to avoid any imbalance.
4. Torque Check: Use a torque wrench to ensure each connection is tightened consistently, minimizing resistance and preventing potential hotspots.
5. Insulation: Install insulation between busbars and other conductive parts to prevent short circuits.

5. Thermal Management

Proper thermal management is crucial, especially in high-capacity packs like this:

• Heat Dissipation: Sodium cells may generate heat during high current discharge. Consider adding heat sinks, thermal pads, or cooling plates between the cells.
• Ventilation: Ensure the battery pack enclosure has ventilation holes or cooling mechanisms to prevent overheating.

6. Testing and Monitoring

After assembling the pack:

1. Voltage Check: Test the voltage across each series and parallel connection to ensure consistency.
2. Load Testing: Apply a controlled load to verify current handling capacity and check for any overheating or abnormal voltage drops.
3. Battery Management System (BMS): Integrate a BMS suited for a 4S3P configuration, capable of monitoring cell voltages, temperatures, and balancing cells as needed for long-term reliability.

Contact

+