Cell-to-Pack (CTP)
Cell-to-Pack (CTP) is a battery construction technique that places individual cells directly into the battery pack housing, eliminating the traditional intermediate module structure. This reduces structural weight and wasted space, increasing the pack's overall energy density.
How It Works
In a conventional battery pack, cells are first assembled into modules (groups of 8–24 cells with their own casing, wiring, and management electronics), and modules are then assembled into the pack. Each module adds structural material that holds cells but stores no energy.
CTP removes this module layer entirely. Cells are arranged directly within the pack structure, using the pack walls and cross-members for structural support instead of individual module housings. Some CTP designs use large prismatic or blade cells that span the full width of the pack.
BYD's "Blade Battery" is one of the most well-known CTP implementations, using long, thin LFP cells that serve both as energy storage and structural members.
Why It Matters
By eliminating modules, CTP achieves higher volumetric energy density — fitting more energy into the same pack footprint. This can mean longer range without increasing pack size or weight, or maintaining the same range with a smaller, lighter, cheaper pack.
CTP also simplifies manufacturing with fewer components and assembly steps. The approach has been particularly transformative for LFP chemistry, helping compensate for LFP's lower cell-level energy density compared to NMC.
Common Values
- Space utilization: 60–67% (CTP) vs 40–50% (traditional modular)
- Pack energy density improvement: 10–20% over modular packs
- Notable implementations: BYD Blade Battery, CATL CTP 3.0, Tesla structural pack
- Evolution: Cell-to-Chassis (CTC) integrates the pack into the vehicle floor structure