CATL says removing the module from a battery pack cut the number of parts by 40%

How a module wastes space inside a pack

A battery pack sits inside an electric car and holds many battery cells wired together to store the energy the car uses. For years, before the cells went into the pack, they were mounted into a middle layer called a module. Battery Design, an independent battery engineering reference site, explains that a module needs extra material to hold cells steady when handled and needs empty space around it for build tolerance, meaning the small gaps engineers leave so the parts fit correctly during assembly. Wiring cells straight into the pack instead is called cell to pack design. CATL, a battery maker, says it built the first pack of this kind in 2019, reaching what it calls a volume utilization efficiency of over 50%, meaning over 50% of the space inside the pack was filled with cells rather than casing, wiring or the gaps a module needs.

What CATL says its newest pack does

CATL called its newest cell to pack design Qilin, launched in 2022. The company says it reaches a volume utilization efficiency of 72%, which it calls record breaking, up from the over 50% level of its first module free pack in 2019. CATL states this design also reaches an energy density, or how much energy the pack holds for its weight, of up to 255 watt hours per kilogram, enough it says for a range of over 1,000 kilometres. An independent trade press account of the same launch, from E Mobility Engineering, repeats the 72% and 255 watt hour figures without adding a reason to doubt them.

What CATL says the redesign cut

On a separate page, Battery Design lists what it says are figures CATL claims for cell to pack design, not shown on any CATL page reachable today, a 20% to 30% increase in the share of a pack filled with cells, a 40% reduction in the number of parts in a battery pack, and a 50% increase in production efficiency, meaning how many packs the company can build in a given time.

What BYD says about its own design

BYD, another battery and car maker, calls its version of the same idea Cell to Pack too. The company says removing the module raised usable space inside its Blade Battery pack by 50%, though it does not state what share of the pack was usable space before the change. Two manufacturers making a similar claim about the same design choice, each in its own words, is the strongest sign available that removing the module is a real material saving rather than marketing from a single company, though neither figure is checked by anyone outside the company that states it.

What an independent count shows

Battery Design also tracks pack level energy density, independent of which pack design a car uses, across a database of electric cars going back to 2019. It found the fleet average climbed from about 146 watt hours per kilogram in 2019 to about 162 today, and that a small group of 5 vehicles from 2026 already averages about 175.

This rise cannot be credited to module removal alone. Battery chemistry has also improved over the same years. But the years match the years cell to pack design has spread, since CATL first launched it in 2019, toward becoming close to standard practice among the largest battery makers.