Shark Attack! Breaking Down BYD’s Battery Pack

Summary

In this three-day Monro Live teardown, Al Styer (VP of Technology) dissects a BYD Shark hybrid battery pack, highlighting its unusual top-side AC cooling, blade-style LFP cells, and an electric heating grid. He notes thoughtful engineering details—encapsulated fasteners, perimeter adhesive, foam padding, vents, and an AC manifold built into the cover. The team carefully cut open the glued pack to extract laser-welded busbars, a BMS with cell-balancing tabs, and a flex circuit that reroutes current between sides. The module contains 114 blade cells (57 per module) with ~30 kW, 365 V DC and an 81 Ah rating—challenging but revealing work for EV tech fans.

Takeaways

• 😀 The BYD Shark Hybrid battery pack is AC cooled, with cooling channels positioned on the top, a unique approach compared to typical bottom-cooling designs.
• 😀 The battery pack uses long, thin Blade Cells, approximately 3/8 of an inch wide, connected in series for energy storage.
• 😀 The battery pack's top features an electric grid designed for heating the cells, which is a crucial function alongside cooling.
• 😀 A green sealing compound is applied around the perimeter and center of the battery pack to prevent leakage and enhance safety.
• 😀 The pack uses encapsulated fasteners to avoid leakage, a feature that is visible in the sealing of all threaded fasteners.
• 😀 A foam pad adheres to the module, likely for structural support or additional insulation.
• 😀 Two vents are present, one on each side of the battery pack, for improved air circulation and temperature regulation.
• 😀 The cover has dedicated ports for AC cooling, which connect to an AC manifold and potentially high-voltage and DC connections.
• 😀 The battery tear-down involved careful disconnection of bus bars and communication wires, followed by a complex extraction process using a saw.
• 😀 The blade battery cells are Lithium Iron Phosphate (LiFePO4), with a total of 114 cells per module, delivering around 30 kWh of energy at 365V DC and 81 Ah.
• 😀 The Battery Management System (BMS) monitors cell voltages and balances them to ensure uniformity, preventing over-discharge or overcharge of any single cell.
• 😀 The design uses flexible circuits within the battery to connect cells, a unique approach compared to using traditional wired connections or flex circuits on both sides.

Q & A

What is the unique cooling feature of the BYD Shark Hybrid battery pack?

The BYD Shark Hybrid battery pack uses an AC cooling system located on the top side of the battery, which is different from the more common bottom cooling methods seen in other EV batteries like Tesla.

What is the significance of the 'blade cell' used in the BYD Shark Hybrid battery?

The blade cell is a long, thin lithium-ion phosphate cell, about 0.38 inches wide, which is arranged in series. This design is intended to improve energy density and performance in the battery pack.

How does the electric grid on top of the battery help with its performance?

The electric grid on top of the battery pack serves as a heating element, helping to regulate the temperature of the battery. It ensures that the cells stay within an optimal temperature range for performance and safety.

Why is the green adhesive compound used in the BYD Shark Hybrid battery pack?

The green adhesive compound is used to seal the perimeter of the battery pack to prevent leakage. It also secures the fasteners and the overall integrity of the pack.

What is the purpose of the foam pad adhered to the module in the battery pack?

The foam pad serves as an insulating material that provides additional protection and contributes to the structural integrity of the battery pack.

What is the role of the Battery Management System (BMS) in the BYD Shark Hybrid battery?

The BMS monitors the voltage of each individual cell in the battery pack, balancing the cells by discharging them if necessary to keep all cells at an equal voltage level, which is crucial for battery longevity and efficiency.

What is the challenge faced in removing the battery from the pack?

One of the main challenges in removing the battery was that the cells were glued down with adhesive, which required a lot of effort to pry them loose, in addition to the complex process of removing bus bars and other connections.

How are the cells in the BYD Shark Hybrid battery connected?

The cells are connected in series, with positive and negative connections running along the length of the module. Bus bars, which are laser-welded to each cell, facilitate the flow of electricity between the cells.

What is the function of the Flex circuit used in the BYD Shark Hybrid battery?

The Flex circuit is used to run current through the battery pack. It connects the positive and negative sides of the cells and provides an innovative way to transfer current through the pack, which is different from the typical dual-sided Flex circuits used in other designs.

What is the reason for using a skill saw to cut open the battery pack?

A skill saw with a metal cutting blade was used to carefully cut through the battery pack casing, as the battery was tightly glued inside. This method allowed for the removal of the pack with minimal risk of damaging the cells or causing an electrical short.