What Is a Cell-to-Pack Battery Design?
Figures on this page are drawn from CATL’s and BYD’s launch material, a peer-reviewed RWTH Aachen teardown of the Blade Battery, Munro’s Tesla structural-pack teardown, and Reuters reporting of Thatcham insurance research.
Cell-to-pack is the packaging change that quietly redesigned the EV battery between 2019 and today.
For the industry’s first decade, every EV battery was built the same way: cells into modules, modules into a pack. Cell-to-pack (CTP) deletes the middle step. The cells go straight into the pack, the space the modules used becomes room for more cells, and the pack gets cheaper to build and denser in energy. CATL launched the first CTP design in 2019, BYD followed with the Blade Battery in 2020, and the idea has since spread to almost every new platform, with a further step, cell-to-chassis, already in production.
This guide explains how CTP works, how the generations differ, where the headline percentages actually come from, and the trade the design makes: the same integration that saves space also makes the pack much harder to repair.
Quick answer
Cell-to-pack (CTP) is a battery design that skips the module stage: instead of grouping cells into modules and modules into a pack, the cells are built directly into the pack itself. Removing the module housings frees space for more cells, so more of the pack’s volume stores energy.
Key figures:
Volume utilisation: around 40% in module-era packs, about 55% in CATL’s first CTP generation, 72% in its third (maker’s figures) · Parts removed: about 40% fewer pack components (CATL) · First CTP design: CATL, 2019 · Best-known example: BYD’s Blade Battery, 2020
What is the traditional battery design?
In a traditional pack, cells are grouped into modules first, and the modules are then assembled into the pack — an arrangement called cell-to-module-to-pack, or CTM.
Modules made early EVs serviceable and safe to build: each module is a sealed, testable unit with its own housing, wiring and connections, and a faulty module can be swapped without scrapping the pack. The cost is packaging. Module walls, frames and duplicate connectors take up room that stores no energy, and in module-era packs only around 40% of the pack’s volume was typically active cell material.
What is cell-to-pack design?
Cell-to-pack removes the module housings and fixes the cells directly into the pack structure, so the pack itself does the job the modules used to do.
Without module walls between them, cells can be longer, packed tighter and cooled by plates built into the pack floor. In most CTP designs the cells are bonded into the tray with structural adhesive and connected by welded busbars, and in BYD’s Blade design the long cells themselves act as beams that stiffen the pack. The pack remains a separate, removable unit — that is what separates CTP from cell-to-chassis, covered below. The battery management system, cooling and crash structure are all still there; only the intermediate packaging is gone.
CTP vs CTM comparison
The honest comparison is not one number but a direction: CTP trades serviceability for space, weight and cost.
| Cell-to-module (CTM) | Cell-to-pack (CTP) | |
|---|---|---|
| Structure | Cells grouped into modules, modules into the pack | Cells built directly into the pack |
| Volume utilisation | Around 40% in module-era packs | About 55% (CATL generation 1) up to 72% (CATL Qilin), maker’s figures |
| Parts | Module housings, frames and duplicate connectors | About 40% fewer pack components (CATL) |
| Repair | A faulty module can be replaced on its own | Cells are bonded in; repair usually means major disassembly or a new pack |
| Examples | Most EVs of the 2010s | CATL CTP/Qilin packs, BYD Blade Battery |
Who pioneered cell-to-pack?
CATL launched the first cell-to-pack design at the Frankfurt motor show in September 2019, and BYD’s Blade Battery a few months later made the idea famous.
CATL’s first generation removed the modules entirely — it was billed as the world’s first module-free pack — and CATL claimed 10 to 15% higher mass energy density, 15 to 20% better volume utilisation, 40% fewer parts and 50% higher production efficiency; its own later figures put the first generation’s volume utilisation at a little over 50%.
A second generation followed without published specifications. The third generation, launched in June 2022 under the name Qilin (spelled with a Q), claims 72% volume utilisation and up to 255 Wh/kg with nickel cells or 160 Wh/kg with LFP, plus 13% more power than a 4680-based pack of the same size. Those are CATL’s figures: the first production Qilin pack, in the Zeekr 001, was filed with China’s MIIT at 200 Wh/kg.
BYD’s Blade Battery, launched in March 2020, took a different route to the same idea: very long, thin LFP cells that span the pack and double as its structure, raising space utilisation from about 40% to about 60% by BYD’s account. Teardown measurement by RWTH Aachen researchers put the production blade cells at 965 mm long — the “up to 2.5 metres” figure sometimes quoted comes from BYD’s patent range, not from a production car.
BYD’s launch film of a nail piercing a blade cell without fire was a demonstration, not a certification; China’s GB 38031-2020 standard had already dropped the standalone nail-penetration test. Blade 2.0 followed in March 2026 with 1,500 kW flash charging, and filings for its first production pack list LFP chemistry, as with the original.
What is cell-to-chassis (CTC)?
Cell-to-chassis goes one step further than CTP: the cells are built into the car’s structure itself, and there is no separate pack to remove.
Tesla’s structural battery pack is the best-known example. Announced at Battery Day in September 2020 and shipped in the Giga Texas Model Y from April 2022, it bonds 4680 cells inside a steel pack enclosure that also forms the car’s floor, working with the front and rear castings. Tesla’s claimed savings — 10% mass reduction, 14% more range opportunity and 370 fewer parts — are vehicle-level figures for the pack and castings together, and the enclosure was not eliminated: the cells sit inside it, set in structural foam.
Leapmotor claimed the first mass-produced cell-to-chassis design in April 2022 with its C01 sedan. BYD markets its own version as cell-to-body (CTB), used in the Seal. Calling Tesla’s design “CTP” is a common error: the pack is structural, which is precisely the CTC idea.
Advantages of cell-to-pack
The advantages all flow from the same deletion: less packaging means more cell, fewer parts and a cheaper build.
More of the pack’s volume stores energy, so a CTP car can carry more range in the same space or the same range in a smaller, lighter pack. Fewer housings and connectors cut both cost and assembly time, and long cells or bonded cells can stiffen the pack in ways modules could not. These are the gains that made CTP the default direction for new platforms within about three years of CATL’s launch.
Disadvantages: repair, insurance and heat
The disadvantage is the mirror image of the advantage: a pack whose cells are bonded in cannot be opened up and fixed piece by piece.
In a module pack, one failed module is a module-sized bill. In a bonded CTP or structural pack, a single failed cell can mean replacing the whole pack. Reviewing Munro’s teardown of Tesla’s structural pack in July 2022, engineer Cory Steuben concluded that “the repairability of this is essentially zero”, and Tesla’s own pack-design director later graded that pack a “D” for serviceability. Insurers price the risk in: Reuters reported Thatcham Research figures in March 2023 showing EV insurance claims averaging 25.5% more expensive than combustion cars, with repairs taking 14% longer, and packs being written off after minor damage because assessing them is so hard.
Designers also lose the module as a firebreak, so thermal-runaway propagation has to be managed with cell spacing, barriers and venting designed into the pack itself, and bonded packs are harder to separate for recycling. Not every CTP design is equally sealed — some keep large replaceable sections — but the direction of the trade is the same everywhere.
Which EVs use cell-to-pack?
In the United States, the honest answer is narrower than most lists suggest: no US-sold car uses a CATL Qilin or BYD Blade pack today.
Qilin packs power Chinese-market cars such as the Zeekr 001, and Blade packs power BYD’s own range and the Toyota bZ3 — none of which are sold in the US. Tesla’s Berlin factory built Model Y rear-wheel-drive cars with BYD blade cells from May 2023, again not a US car.
The US example of the architecture’s direction is Tesla’s structural pack in the Giga Texas Model Y, which is a cell-to-chassis design rather than CTP proper. Two common mislabels are worth avoiding: Hyundai and Kia’s E-GMP cars (Ioniq 5, EV6) use a module-based pack, not CTP, and lists that name cell suppliers such as LG Energy Solution or SK On as “CTP cars” are describing technology programmes, not vehicles you can buy.
Is cell-to-pack the future?
Cell-to-pack is less the future than the present: the open questions now are how far integration goes, and whether repairability gets designed back in.
Every major maker now ships or is developing packs with fewer, larger building blocks, and cell-to-chassis designs are in production at Tesla, BYD and Leapmotor. The counter-pressure is real, though: insurance costs, right-to-repair debates and recycling rules all push toward packs that can be opened and serviced. The likely settlement is what the better designs already do — integration where it saves space, with serviceable sections where failure is most likely.
Frequently asked questions
What is the difference between cell-to-pack and cell-to-module?
Cell-to-module (CTM) groups cells into sealed modules and then assembles the modules into a pack; cell-to-pack (CTP) builds the cells directly into the pack. CTP uses the pack’s volume far better — about 55 to 72% utilisation in CATL’s generations, against around 40% for module-era packs — but gives up module-level repair.
What is the difference between CTP and CTC?
In CTP the cells fill a pack that is still a separate, removable unit. In cell-to-chassis (CTC) the cells are built into the vehicle’s structure, as in Tesla’s structural pack and BYD’s cell-to-body (CTB) designs, so there is no separate pack to unbolt.
Which generation of CATL CTP is Qilin?
Qilin is CATL’s third-generation CTP, launched in June 2022, claiming 72% volume utilisation and up to 255 Wh/kg with nickel cells. The second generation was an interim step for which CATL published no specifications.
Can a cell-to-pack battery be repaired?
Usually not at cell level. Because the cells are bonded into the pack, a failure typically means major disassembly or a complete pack replacement, which is why teardown specialists rate the most integrated designs so poorly for repairability. Some CTP packs keep larger replaceable sections, which softens but does not remove the problem.
Does Tesla use cell-to-pack?
Tesla’s structural pack is a cell-to-chassis design, not CTP: the 4680 cells are bonded inside a steel enclosure that forms part of the car’s structure. It pursues the same goal — less packaging, more cell — one step further.
Is the BYD Blade Battery a cell-to-pack design?
Yes. The Blade’s long LFP cells span the pack and act as structural beams, which is a cell-to-pack design by any definition; BYD simply markets it under its own name, and its successor design is sold as cell-to-body (CTB).
Conclusion
Cell-to-pack won because the module was mostly packaging — and the industry is still working out what that victory costs. Deleting the module stage bought real gains in space, weight and cost, and every figure in this guide traces to the maker who claimed it, because CTP percentages without an owner are how the errors in most articles on this topic got there. The design’s open account is repairability: until integrated packs can be fixed at reasonable cost, the cheapest pack to build may also be the most expensive one to repair.
