CAP-XX v. Maxwell Technologies: Ultracapacitor Patent Dispute Settled After 1,694 Days
Australian energy-storage specialist CAP-XX, Ltd. filed suit in Delaware against Maxwell Technologies asserting two ultracapacitor patents across more than 55 accused product SKUs. The parties ultimately reached a confidential settlement, producing a stipulated dismissal with prejudice after nearly four and a half years of litigation.
CAP-XX’s Ultracapacitor Patents Meet Maxwell’s Broad Product Portfolio
On 16 September 2019, CAP-XX, Ltd., an Australian developer of supercapacitor technology, filed an infringement action against Maxwell Technologies, Inc. in the U.S. District Court for the District of Delaware (Case No. 1:19-cv-01733), presided over by Judge Jennifer L. Hall. CAP-XX asserted two patents — US7382600B2 and US6920034B2 — covering ultracapacitor electrode structures and cell designs, against an exceptionally broad accused product set spanning more than 55 Maxwell BCAP and BMOD ultracapacitor SKUs, as well as GEN and ULTRA series modules.
The litigation concluded on 6 May 2024 via a Stipulation of Dismissal reflecting a confidential settlement. Under the court’s order, CAP-XX’s infringement claims were dismissed with prejudice, extinguishing any right to re-file on the same claims. Maxwell’s counterclaims and defenses, by contrast, were dismissed without prejudice, preserving Maxwell’s theoretical ability to revive those positions in a future proceeding. Each party was ordered to bear its own attorneys’ fees, expenses, and costs — a cost-neutrality provision that is common in negotiated settlements.
At 1,694 days, this case ran significantly longer than the median patent case in Delaware, suggesting the parties engaged in substantive discovery and potentially claim-construction proceedings before settlement. The financial terms of any license or lump-sum payment remain undisclosed. Notably, Maxwell Technologies was acquired by Tesla, Inc. in 2019 — the same year the suit was filed — adding a significant commercial dimension to the dispute that may have influenced settlement dynamics and timing.
Filing to Case Dismissed in 1694 days
1,694 days — nearly 4.7 years, well above median for multi-patent Delaware infringement actions
Stipulated dismissal explained: what the settlement order means for both parties
Dismissal with prejudice bars CAP-XX from re-filing these claims
A dismissal with prejudice under Federal Rule of Civil Procedure 41 is a final adjudication on the merits for preclusion purposes. CAP-XX cannot reassert US7382600B2 or US6920034B2 against Maxwell (now Tesla) on the same accused BCAP and BMOD products in a future action. The settlement is typically accompanied by a license or covenant not to sue, the financial terms of which are not public.
Final — no re-filing on same claimsCAP-XX secures certainty; confidential terms likely include compensation
By accepting dismissal with prejudice, CAP-XX exchanged its litigation rights for settlement consideration whose value is undisclosed. The outcome suggests CAP-XX extracted some form of value — whether a lump-sum payment, royalty stream, or cross-license — rather than abandoning the case outright. The with-prejudice posture is consistent with a fully resolved business deal rather than a capitulation.
Settlement value undisclosedMaxwell’s counterclaims survive — dismissed without prejudice
Maxwell’s counterclaims and defenses were dismissed without prejudice, meaning they were not adjudicated on the merits and could theoretically be revived in future proceedings. This asymmetry — plaintiff’s claims dismissed with prejudice, defendant’s without — is a common settlement feature that gives the accused party a degree of residual leverage. Each party bearing its own costs suggests a balanced negotiating outcome.
Counterclaims preserved (no prejudice)Tesla inherits settlement; ultracapacitor IP landscape tightened
Maxwell was acquired by Tesla in 2019, making Tesla the effective party on the defence side throughout most of this litigation. The settlement resolves CAP-XX’s claims against what is now a Tesla subsidiary, but the without-prejudice dismissal of Maxwell’s counterclaims means Tesla retains latent invalidity arguments. Competitors in the ultracapacitor space should note that both asserted patents remain formally in force, and their enforceability has not been tested to a final merits ruling.
Tesla inherits settlement termsFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | CAP-XX, Ltd. | Company | Australian ultracapacitor technology developer — holder of US7382600B2 and US6920034B2Search in Eureka ↗ |
| Defendant | Maxwell Technologies | Company | Maxwell Technologies: ultracapacitor and energy-storage module manufacturer, acquired by Tesla in 2019Search in Eureka ↗ |
| Plaintiff counsel | Adam Yowell | Attorney | Counsel for CAP-XX, Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Alastair J. Warr | Attorney | Counsel for CAP-XX, Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Chris P. Perque | Attorney | Counsel for CAP-XX, Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Jonathan A. Choa | Attorney | Counsel for CAP-XX, Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Philip A. Rovner | Attorney | Counsel for CAP-XX, Ltd.Search in Eureka ↗ |
| Plaintiff law firm | Potter, Anderson & Corroon LLP | Law Firm | Representing CAP-XX, Ltd.Search in Eureka ↗ |
| Defendant counsel | Aamir A. Kazi | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Adam M. Pivovar | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Cheryl T. Burgess | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Daniel R. Gopenko | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Grayson P. Sundermeir | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Jack B. Blumenfeld | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Jeremy A. Tigan | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Kimberly A. Kennedy | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Lauren Keller Katzenellenbogen | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Matthew C. Colvin | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Michael A. Vincent | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Michael K. Friedland | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Ruffin B. Cordell | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Sarah E. Jack | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant counsel | Susan E. Morrison | Attorney | Counsel for Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant law firm | Fish & Richardson PC | Law Firm | Representing Maxwell TechnologiesSearch in Eureka ↗ |
| Defendant law firm | Morris, Nichols, Arsht & Tunnell LLP | Law Firm | Representing Maxwell TechnologiesSearch in Eureka ↗ |
| Presiding judge | Judge Jennifer L. Hall | Judge | Delaware District CourtSearch in Eureka ↗ |
Official order — verbatim text
The court’s order adopts the parties’ stipulation verbatim, creating a legally precise asymmetry: plaintiff CAP-XX’s infringement claims are extinguished with prejudice, while Maxwell’s counterclaims survive in a dormant, without-prejudice state. This structure is consistent with a negotiated settlement in which the accused party preserved optionality on invalidity arguments. The absence of a merits ruling means neither patent’s validity nor infringement has been judicially determined, leaving both patents enforceable against third parties.
US7382600B2 & US6920034B2 — Ultracapacitor Electrode and Cell Architecture Patents
US7382600B2 (application US11/228294) and US6920034B2 (application US10/635775) are CAP-XX patents covering the electrode structures and cell architectures of electrochemical double-layer capacitors — commonly known as ultracapacitors or supercapacitors. These components govern how charge is stored and delivered at high power density. The patents are directed at the physical construction of capacitor cells, including electrode geometry and assembly, which are central to performance characteristics such as capacitance, equivalent series resistance, and cycle life — all critical differentiators in the ultracapacitor market.
Ultracapacitors are increasingly strategic in automotive, grid storage, and industrial applications — particularly following Tesla’s acquisition of Maxwell. Both asserted patents cover foundational cell-level architecture, meaning their claims can potentially read across a wide range of competing products regardless of brand. The 55+ accused Maxwell SKUs demonstrate the breadth of potential coverage. With neither patent having been subjected to a final invalidity ruling, they remain viable enforcement tools for CAP-XX against other market participants until expiry or successful IPR challenge.
Should you run an FTO against US7382600B2 and US6920034B2?
Any company designing or sourcing ultracapacitor cells, modules, or energy-storage systems — particularly those using electrochemical double-layer capacitor architecture — should assess exposure to both CAP-XX patents. The breadth of accused products in this case (3F to 3400F cells, module assemblies, automotive-grade units) suggests claims capable of reading on a wide product spectrum. This is especially relevant for EV drivetrain suppliers, industrial UPS manufacturers, and grid-balancing system developers.
PatSnap Eureka’s FTO Search Agent can map the claim scope of US7382600B2 and US6920034B2 against your product specifications, identify prior art that could support an IPR petition, and flag related family members or continuation patents. Given that Maxwell’s invalidity counterclaims were never adjudicated, a well-researched validity analysis could provide significant commercial leverage for any party facing enforcement of these patents.
Run a freedom-to-operate analysis on US7382600B2 to assess your product’s exposure
Run FTO in Eureka →Similar Ultracapacitor & Energy Storage Patent Cases in Delaware
Explore related patent infringement actions involving ultracapacitor and supercapacitor technology litigated in the Delaware District Court.
What this case signals for the ultracapacitor and energy-storage IP landscape
A long-running Delaware case settled quietly — but the IP dynamics it exposed have lasting implications for anyone competing in ultracapacitor technology.
Maxwell’s BCAP product line faced broad patent exposure across 55+ SKUs
The sheer breadth of accused products — spanning BCAP cells from 3F to 3400F and multiple BMOD module families — signals that CAP-XX’s patents were drafted with wide structural coverage. Any competitor producing similar electrode architectures should treat these patents as live enforcement risks until they expire or are invalidated.
Tesla’s acquisition of Maxwell did not neutralise CAP-XX’s infringement claims
The case proceeded for over four years post-acquisition, suggesting that a change of corporate ownership does not automatically prompt settlement or defensive IP consolidation. IP teams at acquiring companies should conduct immediate FTO audits on target companies’ core product lines before or shortly after close.
CAP-XX v Maxwell — key questions answered
CAP-XX asserted two patents: US7382600B2 and US6920034B2, both covering ultracapacitor electrode structures and electrochemical double-layer capacitor cell architectures. The accused products included over 55 Maxwell BCAP and BMOD ultracapacitor SKUs spanning a wide range of capacitance values and form factors.
The case was resolved through a confidential settlement. On 6 May 2024, the Delaware District Court entered a dismissal order: CAP-XX’s claims were dismissed with prejudice, and Maxwell’s counterclaims and defenses were dismissed without prejudice. Each party bore its own attorneys’ fees and costs. Financial settlement terms were not disclosed in the public record.
CAP-XX’s claims being dismissed with prejudice means it cannot re-file the same patent infringement claims against Maxwell on these products. Maxwell’s counterclaims being dismissed without prejudice means its invalidity and non-infringement arguments were never adjudicated on the merits and could theoretically be raised again in a future proceeding, preserving residual leverage for Maxwell (now Tesla).
Tesla acquired Maxwell in 2019, the same year the suit was filed, making Tesla the effective parent of the defendant throughout most of the litigation. While the public record does not specify Tesla’s direct involvement in the settlement, as Maxwell’s parent Tesla inherited both the litigation exposure and any resulting settlement obligations or licenses. This dynamic may have influenced the case’s extended duration and ultimate resolution.
Yes. A settlement dismissal does not invalidate the patents. Both US7382600B2 and US6920034B2 remain formally in force. Because Maxwell’s invalidity counterclaims were dismissed without prejudice rather than adjudicated, no court has ruled on patent validity. Third parties — including other ultracapacitor manufacturers — remain potentially exposed to enforcement of these patents until they expire or are successfully challenged via IPR or other proceedings.
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