Invinity Packs More Energy Into Its Endurium Flow Battery

Invinity Energy Systems announced an upgraded Endurium flow-battery module on November 9, increasing its stated energy capacity from 342 to 516 kilowatt-hours (kWh), roughly 50 percent. The company also lists peak power of 125 kilowatts (kW) per module. Offered for general sale, the upgrade aims to fit more stored electricity onto a constrained site and reduce the number of modules a customer needs to buy and install. 1,2

The engineering changes include larger tanks for the liquid electrolyte that stores energy, upgraded electrical and power-distribution equipment, and changes to fluid management and control algorithms. The improvement comes from redesigning a packaged battery system around its working fluid. It addresses a practical constraint for factories and renewable-power projects: how much useful storage can fit on the available land. 1

In a vanadium flow battery, liquid from two tanks circulates through a stack of electrochemical cells. Reversible reactions allow the system to accept electricity during charging and return it during discharge. The tanks largely determine how much energy can be stored, while the stack and electrical equipment determine power delivery. That separation gives developers a way to adjust storage duration for a particular job, such as carrying solar generation into the evening. 3,4

At a fixed amount of stored energy, a 50 percent increase per module implies roughly one-third fewer modules, before accounting for whole-unit sizing and the project's power requirement. That is arithmetic from the announced capacity increase. Invinity President Matt Harper described the aim as “fewer modules to buy, install and maintain.” The potential saving extends beyond the containers to the work of connecting and servicing them. 1

The November datasheet shows why a project still needs to be sized around its discharge schedule. Four modules form a string; its higher-power configuration is listed at up to 500 kW of direct-current (DC) power and 2,065 kWh of maximum usable energy. For a six-hour discharge, the same table specifies 302 kW. The peak rating and the sustained output describe different operating conditions, and usable energy varies with the discharge profile. 5

That datasheet gives a DC round-trip efficiency of 68 percent with auxiliary loads included and electrolyte at 35 degrees Celsius; its auxiliary-load note excludes temperature-dependent cooling fans. In operation, losses mean the electricity purchased to charge a battery exceeds the electricity it later returns. The sheet also lists annual energy degradation below 0.2 percent and marks its listed certifications and standards as expected in 2027. Those details belong in a customer's assessment alongside the newly offered module's headline capacity. 5

For a utility or industrial buyer, storage economics depend on what the installation does each day. A battery that shifts energy into a more valuable period earns a different return from one reserved mainly for occasional outages. The United States Department of Energy's flow-battery assessment identifies electrolyte cost and manufacturing scale as continuing development needs, alongside project financing and grid-connection delays. Packing more energy into each module addresses part of that cost problem; the grid connection and the site's operating pattern still shape the project. 4

Invinity's announcement provides no installed price or quantified reduction in total project cost. A comparison with a lithium-ion installation would need the same required power, discharge duration and cycling schedule, together with charging losses and maintenance over the contract term. Customer projects using the upgraded configuration will supply the operating record behind that comparison. Delivery dates, accepted capacity and the cost of keeping the equipment available will show how the denser module performs as an investment in everyday electricity service.

Sources

1. Invinity engineering announcement, module capacities and Matt Harper quotation, November 9, 2026

2. Invinity company announcement via Reach, general-sale status and performance upgrade, November 9, 2026

3. Invinity explanation of vanadium flow-battery operation

4. United States Department of Energy, Flow Batteries Technology Strategy Assessment, July 2023

5. Invinity Endurium datasheet linked from the current product page, November 2026, including performance conditions and certification footnote