VRFB State-of-Charge Estimation Patent Landscape
The VRFB state-of-charge estimation field is in a growth stage, with recent three-year filings running well above the prior window despite annual volume easing from an earlier peak; Europe and the United States are the primary filing destinations. The competitive space is moderately concentrated, with HydraRedox Technology Holdings leading a field that still has room for differentiation in measurement and grid-integration approaches.
HydraRedox leads a moderately concentrated field
HydraRedox Technology Holdings holds the top position with 9 patent records, followed closely by Storion Energy LLC and the University of Limerick, each with 8 patent records, and the two ThyssenKrupp entities combined accounting for 14 patent records across the ranking.
The top five filers account for 35% of the combined total of the hundred largest filers, indicating moderate concentration: no single player dominates, and the gap between the leader and the second and third tier is narrow, leaving the competitive structure genuinely contested.
| # | Applicant | Patent records | Share |
|---|---|---|---|
| 1 | HydraRedox Technology Holdings | 9 | |
| 2 | Storion Energy LLC | 8 | |
| 3 | University of Limerick | 8 | |
| 4 | ThyssenKrupp Industrial Solutions AG | 7 | |
| 5 | ThyssenKrupp AG | 7 | |
| 6 | Imergy Power Systems | 6 | |
| 7 | LG Chem Ltd | 6 | |
| 8 | JD Holdings Inc | 6 | |
| 9 | Largo Clean Energy Corp | 4 | |
| 10 | Liva Power Management Systems GmbH | 4 |
| # | Applicant | Patent records | Share |
|---|---|---|---|
| 11 | Atomic Energy Council Institute of Nuclear Energy Research | 3 | |
| 12 | VRB Energy Inc | 3 | |
| 13 | Aarhus University | 3 | |
| 14 | WattJoule Corp | 2 | |
| 15 | Fraunhofer Society | 2 | |
| 16 | OCI Co Ltd | 2 | |
| 17 | Industry-Academic Cooperation Foundation Chosun University | 2 | |
| 18 | New Well Co Ltd | 2 | |
| 19 | Dalian Rongke Power Co Ltd | 2 | |
| 20 | State Grid Qinghai Electric Power Company | 2 |
The presence of both industrial firms and academic institutions near the top of the ranking signals that fundamental measurement methodology remains an active research frontier, not yet fully appropriated by commercial incumbents.
Patent records from 2024 and 2025 are likely understated due to standard publication lag; the apparent softening in those years should not be read as a real decline in R&D activity. Longer-window growth, applicant concentration, and technology-route coverage are therefore more reliable signals than the latest-year bar alone.
Multi-year growth with a dominant electrochemical core and emerging measurement branches
The annual filing trend and technology composition charts together show a field that expanded sharply on a multi-year basis while remaining anchored in core electrochemical patent classes, with a set of adjacent measurement and grid-systems branches beginning to appear.
Annual filing trend
Filing volume peaked at 16 records in 2017, fell sharply through 2018–2019, then recovered steadily, reaching 14 records in 2022 and 12 in 2024. The three-year recent window is 267% above the prior three-year window, confirming growth-stage dynamics on a multi-year basis. Records from 2024–2025 are understated by publication lag and should be treated as a floor, not a ceiling.
↗ Hover for values · click a bar to ask EurekaTechnology composition
H01M (Batteries, cells and fuel cells) accounts for the overwhelming majority of classification hits, reflecting the electrochemical core of SoC estimation for vanadium flow batteries. G01R (Electric and magnetic measurement) and B60L (Electric vehicle propulsion) appear as secondary branches, with G01N (Material analysis), H02J (Power supply and grid systems), and G01F (Flow, level and volume measuring) representing smaller but technically meaningful adjacent clusters.
↗ Hover for values · click a bar to ask EurekaHighly cited patent families surfaced by the query
Citation-heavy patent families returned by the query. Use this section as citation context, not as a curated list of the most topic-specific patents.
Determining the state of charge of an all-vanadium…
The invention relates to a method for determining the state of charge of a vanadium redox flow cell, in which the concentrations of V4+ and V5+ in the positive electrolyte are determined indirectly by mixing the positive and the negative electrolyte together in specific proportions in order to reduce the V5+ contained in the positive electrolyte. CT… (excerpt from the patent abstract)
Open this patent in Eureka →| # | Patent | Citations |
|---|---|---|
| 1 | Efficient energy storage systems using vanadium re… | 114 |
| 2 | Electrochemical balance in a vanadium flow battery | 35 |
| 3 | Single capacity balancing in a redox flow battery | 27 |
| 4 | Method for determining the state of charge of a va… | 25 |
| 5 | Method for preparing electrolyte for vanadium redo… | 21 |
| 6 | Charge state monitoring of a vanadium redox flow b… | 21 |
| 7 | Method of conducting an all vanadium redox flow ba… | 20 |
| 8 | 钒电池正极电解液荷电状态的原位监测方法 | 20 |
Ranked by total forward citations. Citation counts favour older and broadly cited patent families, and broad or adjacent patents may appear when they match the search scope. Treat this section as citation context, not as a curated list of the most topic-specific patents. Some patent titles may be shown in their original, non-English language where an accurate translation could not be guaranteed.
What the competitive structure means for R&D investment decisions
The combination of growth-stage dynamics, moderate concentration, active academic participation, and dual-continent filing leadership creates a window for targeted differentiation, particularly in measurement methodology and grid-integration applications.
Growth stage — multi-year expansion with annual volatility
The field is classified as Growth: the recent three-year filing window sits 267% above the prior three-year window, confirming sustained expansion at the corpus level. Annual volume has eased from the 2017 peak and fluctuates, but this reflects the small absolute corpus size and publication lag rather than maturity or saturation. Entrants can still establish foundational positions.
Growth stageModerate concentration, narrow tier gaps
The top five filers hold 35% of the hundred largest filers’ combined total, and the gap between the leader (9 patent records) and the second and third positions (8 each) is minimal. This narrow spread means no incumbent has locked in a dominant intellectual property position, and a focused filing program can realistically reach the top tier within a few years.
Moderate concentrationThyssenKrupp entities and Largo–Storion are the most active co-filers
The most active co-filing pair is ThyssenKrupp AG and ThyssenKrupp Industrial Solutions AG, who share 7 jointly filed patent records — the largest collaboration cluster in the corpus. Largo Clean Energy Corp and Storion Energy LLC form a second active pair with 3 jointly filed records. Both collaborations link industrial operators with technical development partners, suggesting that practical deployment experience is being translated into IP.
Industry collaborationEurope and the US are co-equal primary filing destinations
Europe (EPO) and the United States each account for 21 patent records, making them the two principal jurisdictions. China (17 records) and WIPO PCT (16 records) form a secondary tier. Australia, Canada, and South Korea each register single-digit coverage. Teams seeking broad commercial protection should prioritise EPO and USPTO filings, with PCT as a cost-efficient bridging route.
Dual-continent leadGo beyond the landscape: Eureka’s TRIZ Solution agent breaks down an R&D problem and returns patented concept solutions, each with a technical approach and cited patent & literature evidence.
| Applicant | Collaborator | Co-filings |
|---|---|---|
| ThyssenKrupp AG | ThyssenKrupp Industrial Solutions AG | 7 |
| Largo Clean Energy Corp | Storion Energy LLC | 3 |
Co-filing pairs, ranked by the number of jointly-filed patent families.
HydraRedox and Largo Clean Energy lead by volume; Storion Energy is a fast-rising challenger
The leader board splits between established industrial and clean-energy companies and newer entrants that have filed heavily in the most recent window, reshaping the ranking quickly given the small corpus size.
HydraRedox Technology Holdings
HydraRedox holds 9 patent records at the top of the ranking, with technology emphasis concentrated in H01M 8 (fuel cells and flow batteries). Momentum data is not separately listed for HydraRedox in the recent-window analysis, indicating its position was established over a longer filing horizon rather than a single recent surge.
patent records: 9Largo Clean Energy Corp
Largo Clean Energy Corp enters the ranking as a new entrant, with 11 recent patent records and a trend classified as a new entrant surge — a trajectory that, given its small prior base, reflects a deliberate and rapid IP-building program. Its technology focus spans H01M 8 (flow batteries) and B60L 58 and B60L 53 (electric vehicle propulsion), suggesting SoC estimation work that extends toward mobile and vehicle applications. Storion Energy LLC shares the new-entrant trajectory and is Largo’s co-filing partner, adding 8 patent records to the ranking.
patent records: 4| Applicant | Recent (3 yrs) | Trend |
|---|---|---|
| Largo Clean Energy Corp | 11 | ▲ new entrant |
| Storion Energy LLC | 3 | ▲ new entrant |
Under-served measurement and grid-integration branches worth watching
Several IPC classes appear at low frequency relative to the dominant H01M core; these are observations of relative sparsity and are highlighted where they also carry plausible technical value and a credible entry path for VRFB SoC estimation work.
G01R · Electric and magnetic measurement
With 10 patent records and a 7% share of classification hits, G01R is the largest adjacent branch but remains thin relative to H01M. Impedance spectroscopy and voltage-based SoC sensing methods fall naturally under this class; the University of Limerick has already cross-filed into G01R 31, confirming technical plausibility. The low absolute count suggests most applicants are not yet capturing measurement-method claims separately from electrochemical claims, leaving room for differentiated filings.
Search this in Eureka →H02J · Power supply and grid systems
H02J appears in only 5 patent records (4% share), despite the obvious relevance of VRFB SoC data to grid dispatch, frequency regulation, and energy management systems. As grid-scale VRFB deployments grow, SoC estimation integrated with grid control architectures is a technically and commercially valuable combination. State Grid Qinghai Electric Power Company is already present in the corpus, but the branch remains sparsely filed, suggesting an entry path for applicants with grid-integration expertise.
Search this in Eureka →How leading filers differ by technology route
Route coverage across the main technology branches in the current evidence set.
| Player | H01M 8 · Batteries, cells & fuel cells | G01R 31 · Electric & magnetic measurement | H01M 4 · Batteries, cells & fuel cells | B60L 58 · Electric vehicle propulsion | H01M 10 · Batteries, cells & fuel cells |
|---|---|---|---|---|---|
| Largo Clean Energy Corp | Strong · 10 | Absent | Absent | Strong · 6 | Absent |
| HydraRedox Technology Holdings | Strong · 8 | Absent | Strong · 6 | Absent | Absent |
| University of Limerick | Strong · 8 | Moderate · 2 | Absent | Absent | Absent |
| ThyssenKrupp Industrial Solutions AG | Strong · 7 | Absent | Absent | Absent | Absent |
| ThyssenKrupp AG | Strong · 7 | Absent | Absent | Absent | Absent |
| JD Holdings Inc | Strong · 6 | Absent | Absent | Absent | Absent |
| LG Chem Ltd | Strong · 6 | Absent | Absent | Absent | Absent |
Frequently asked questions
The evidence corpus contains 63 patent families in scope for VRFB state-of-charge estimation, spanning filings from multiple jurisdictions globally.
HydraRedox Technology Holdings leads with 9 patent records, followed by Storion Energy LLC and the University of Limerick, each with 8 patent records, and the two ThyssenKrupp entities with 7 patent records each.
Europe (EPO) and the United States are tied as the primary filing destinations, each with 21 patent records. China follows with 17 records and WIPO PCT with 16, forming a secondary tier.
The field is classified as Growth. The recent three-year filing window is 267% above the prior three-year window, confirming multi-year expansion. Annual volume has eased from a 2017 peak, and the most recent years are additionally understated by publication lag.
The most-cited work in the corpus is titled ‘Efficient energy storage systems using vanadium redox…’, which has accumulated 114 citations, making it the foundational reference by a substantial margin over the next-cited work at 35 citations.
The G01R (Electric and magnetic measurement) and H02J (Power supply and grid systems) branches are the most credible adjacent areas: both have low filing counts relative to the H01M core, carry direct technical relevance to SoC estimation, and have limited incumbent coverage in the corpus.
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Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
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