CATL at Smarter E: We are entering the era of 9 MWh systems

On the first day of the Smarter E show in Munich, CATL, the world’s largest battery manufacturer, unveiled the Tener Stack, which it describes as the world’s first 9 MWh ultra-large-capacity energy storage system.

“The system was developed in response to customer demand for high-capacity products that are also easy to transport,” Hank Zhao, CTO of ESS Europe at CATL, said during a press briefing.

The Tener Stack is a two-in-one solution featuring two 20-foot containers stacked vertically. Each container weighs less than 36 tons and meets transportation standards in 99% of countries worldwide, the manufacturer said.

This significantly improves the product’s transportability, requiring only standard lifting equipment and minimizing the risk of tipping during road transport.

This latest product continues CATL’s Tener series, first introduced in 2024. The original flagship model featured 6.25 MW capacity in a 20-foot equivalent unit (TEU) container and was touted as the first mass-produced energy storage system with zero degradation in the first five years of operation.

The manufacturer’s latest product incorporates 565 Ah lithium iron phosphate (LFP) cells, the same as the earlier Tener version, but introduces several key advantages. It achieves a 45% improvement in volume utilization and a 50% increase in projected energy density.

It is also said to deliver safety advancements, with a 40% improvement in detection sensitivity and a 35% increase in fire extinguishing response speed. The risk of thermal runaway is reduced with the introduction of a 10% lower flammable gas alarm threshold and a fire resistance duration of up to two hours.

The Tener Stack also simplifies AC-side configurations and supports both centralized and string inverter architectures. Each stacked container provides at least two DC outputs, allowing for more flexible integration with various power conversion systems.

The new system offers significant economic advantages for large-scale deployments. At an 800 MWh site, for example, switching from a 6 MWh to a 9 MWh system would reduce the number of containers from 34 to 23, the number of PCS from 17 to 12, and the land area needed from 4653 m2 to 2753 m2. CATL calculates that this would save up to 20% on the initial project investment.

“9 MWh is not the upper limit for utility-scale BESS products,” Zhao said. “Higher capacities, including double-digit MWh systems, are possible and will depend on customer demand. What we’re hearing is a clear need for easier transportability and higher energy density per square meter — and that’s what drove the development of the Tener Stack. However, the theoretical ceiling for energy density is ultimately defined by the LFP chemistry.”