Bunker Hill Tech LLC v. Nissan Motor Co Ltd

I. Executive Summary and Procedural Information

• Parties & Counsel:
  • Plaintiff: Bunker Hill Technologies, LLC (Texas)
  • Defendant: Nissan Motor Co., Ltd. (Japan)
  • Plaintiff's Counsel: Nelson Bumgardner Conroy PC
• Case Identification: 2:26-cv-00230, E.D. Tex., 03/20/2026
• Venue Allegations: Plaintiff alleges that venue is proper because Defendant is a foreign corporation and may be sued in any judicial district pursuant to 28 U.S.C. § 1391(c)(3).
• Core Dispute: Plaintiff alleges that Defendant's electric and hybrid-electric vehicles infringe six patents related to onboard power electronics and energy transfer systems for vehicle charging.
• Technical Context: The technology concerns integrated charging systems for electric vehicles (EVs), a field of significant importance for reducing vehicle cost, weight, and complexity in the expanding EV market.
• Key Procedural History: The complaint alleges that Plaintiff's licensing agent first communicated with Defendant regarding a potential license on March 3, 2025. It further alleges that claim charts demonstrating infringement for five of the six asserted patents were provided to Defendant on July 21, 2025, with a chart for the sixth patent provided on November 13, 2025. These allegations form the basis for Plaintiff's claim of pre-suit knowledge and willful infringement.

Case Timeline

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 8,030,884 - "Apparatus for transferring energy using onboard power electronics and method of manufacturing same" (issued Oct. 4, 2011)

The Invention Explained

• Problem Addressed: The patent's background describes that dedicated battery charging circuitry in plug-in electric vehicles adds "extra cost and weight to the vehicle" '884 Patent, col. 1:49-51 The stated goal is to provide an apparatus that reduces the number of components dedicated solely to charging from an external source '884 Patent, col. 1:52-59
• The Patented Solution: The invention proposes re-using a vehicle's existing onboard power electronics, which are normally used to power the motor, to also manage the charging process. The system uses a "bi-directional voltage modification assembly" coupled to the vehicle's energy storage device and a charge bus, along with a controller that monitors and controls the transfer of energy from an external voltage source to the battery '884 Patent, abstract '884 Patent, col. 2:1-11 This dual-use functionality aims to eliminate redundant hardware.
• Technical Importance: This integrated approach to charging architecture could enable lighter, less complex, and more cost-effective electric vehicle designs by leveraging powertrain components for both driving and charging functions.

Key Claims at a Glance

• The complaint asserts at least independent claim 20 Compl. ¶32
• Claim 20 Elements:
  • A system comprising: a charge bus configured to receive charging energy from a voltage source;
  • an energy storage device configured to output a DC voltage and coupled to the charge bus;
  • a first bi-directional voltage modification assembly coupled to the charge bus;
  • a controller configured to: monitor the transfer of charging energy, compare it with a threshold (such as battery voltage), and control the modification assembly to modify the charging energy after the threshold is crossed.
• The complaint reserves the right to assert other claims by alleging infringement of "one or more claims" Compl. ¶31

U.S. Patent No. 8,487,582 - "Apparatus for transferring energy using onboard power electronics and method of manufacturing same" (issued July 16, 2013)

The Invention Explained

• Problem Addressed: As a continuation of the application leading to the '884 Patent, this patent addresses the same problem: the additional cost and weight of dedicated charging components in electric vehicles '582 Patent, col. 1:44-51
• The Patented Solution: The solution is an apparatus that integrates charging functions into the vehicle's powertrain electronics. It comprises an energy storage device, a bi-directional voltage modification assembly, and a charge bus that is coupleable to a "high-impedance voltage source." A controller monitors the energy transfer from this source and modifies the charging voltage or current accordingly '582 Patent, abstract '582 Patent, col. 2:1-11
• Technical Importance: The invention's significance lies in its method for enabling charging from common, high-impedance sources like a standard utility grid outlet without requiring separate, bulky charging hardware.

Key Claims at a Glance

• The complaint asserts at least independent claim 1 Compl. ¶46
• Claim 1 Elements:
  • An apparatus comprising: an energy storage device configured to output a DC voltage;
  • a bi-directional voltage modification assembly coupled to the energy storage device;
  • a charge bus coupled to the energy storage device and the modification assembly, where the charge bus is coupleable to a high-impedance voltage source;
  • a controller configured to: monitor the transfer of charging energy from the high-impedance source and modify the voltage or current of that energy based on the monitoring.
• The complaint alleges infringement of "one or more claims," preserving the option to assert others Compl. ¶45

U.S. Patent No. 9,809,121 ('121 Patent) - "Apparatus for energy transfer using converter and method of manufacturing same" (issued November 7, 2017)

• Technology Synopsis: This patent discloses a vehicle charging architecture that utilizes a connection system capable of handling both a first and second connection (e.g., AC and DC) at different charging rates. The system employs a series of DC converters to first boost an input voltage to an intermediate level and then buck that intermediate voltage to a final output voltage suitable for charging the vehicle's energy storage device '121 Patent, abstract
• Asserted Claims: At least claim 7 Compl. ¶60
• Accused Features: The complaint alleges that the accused vehicles feature a connection system with both "Normal charge" (AC) and "DC Fast Charge" (DC) inputs, which operate at different charging rates Compl. ¶¶62-63 The infringement allegation further points to the vehicles' use of boost and buck DC converters within their charging subsystems Compl. ¶64

U.S. Patent No. 9,914,365 ('365 Patent) - "Apparatus and method for rapid charging using shared power electronics" (issued March 13, 2018)

• Technology Synopsis: The patent describes a vehicle charging system comprising a connection system for both DC and AC inputs, each providing different charging rates. The system architecture includes an AC/DC converter and a plurality of DC converters configured to perform boost and buck operations to manage charging from these distinct sources '365 Patent, claim 1
• Asserted Claims: At least claim 1 Compl. ¶74
• Accused Features: The complaint alleges the accused vehicles contain a connection system compatible with both AC and DC charging inputs, an AC/DC converter, and multiple DC converters that perform boost and buck functions to manage charging voltage Compl. ¶¶76-78

U.S. Patent No. 9,975,439 ('439 Patent) - "Apparatus for energy transfer using converter and method of manufacturing same" (issued May 22, 2018)

• Technology Synopsis: The patent claims a comprehensive vehicle system that includes an energy storage device, a first voltage converter, a traction drive (comprising an inverter and motor), and an onboard charging system. A key aspect of the claimed charging system is its use of a second voltage converter to boost an input voltage and a third voltage converter to buck the resulting intermediate voltage to charge the battery '439 Patent, claim 1
• Asserted Claims: At least claim 1 Compl. ¶88
• Accused Features: The infringement allegations map the claimed system onto the accused vehicles, identifying the Li-ion battery, a DC/DC converter, the traction motor/inverter, and a charging system that allegedly uses boost and buck converters Compl. ¶¶89-93

U.S. Patent No. 10,604,023 ('023 Patent) - "Apparatus for energy transfer using converter and method of manufacturing same" (issued March 31, 2020)

• Technology Synopsis: This patent claims a vehicle system similar to the '439 Patent, but with the specific limitation of a "first switching device" coupling a first voltage converter to the energy storage device. The claimed charging system also includes a receptacle and second and third voltage converters for boost and buck operations '023 Patent, claim 1
• Asserted Claims: At least claim 1 Compl. ¶103
• Accused Features: The complaint alleges the accused vehicles contain the claimed system, specifically identifying a "contactor" as the "first switching device" Compl. ¶105 It also alleges the presence of the multi-stage (boost/buck) charging system Compl. ¶108

III. The Accused Instrumentality

Product Identification

• The accused instrumentalities are "each Nissan- or Infiniti-branded vehicle having electric or hybrid-electric powertrain systems" Compl. p. 2, fn. 1 Specific examples cited include the 2023-25 Nissan Ariya, 2018-26 Nissan Leaf, and 2026 Nissan Rogue Compl. p. 2, fn. 1

Functionality and Market Context

• The complaint describes the accused vehicles as incorporating a powertrain and charging system that includes a high-voltage battery (e.g., a 400V Li-ion battery), an onboard charger, a DC/DC converter, high-voltage wire harnesses, and a battery controller (Compl. ¶33; Compl. ¶34; Compl. ¶35; Compl. ¶36). The system is alleged to manage charging by monitoring the battery's state and using the power electronics to modify charging voltage and current, such as by stopping the charge when the battery reaches a "desired value" Compl. ¶36 The complaint includes a screenshot from a vehicle manual describing the "CHARGE LIMIT" function, which stops the vehicle from charging when it reaches a user-set level Compl. p. 15 These vehicles represent Defendant's entries in the competitive and growing global market for electric and hybrid automobiles.

IV. Analysis of Infringement Allegations

'884 Patent Infringement Allegations

Identified Points of Contention

• Scope Questions: A potential point of contention may be whether the accused "bi-directional DC/DC converter" Compl. ¶35 corresponds to the "first bi-directional voltage modification assembly" as contemplated by the patent. The defense may argue that the specification's description of this assembly as a "bi-directional DC-to-AC voltage inverter" in one embodiment limits the claim's scope to the main inverter, not a separate DC/DC converter '884 Patent, col. 2:64-66 The complaint illustrates this element with a diagram labeling the "DC/DC converter" as the claimed assembly Compl. p. 13
• Technical Questions: The analysis may focus on whether the accused "battery controller" performs the specific three-step "monitor, compare, control" sequence as required by the claim. The complaint provides a vehicle manual excerpt showing a "CHARGE LIMIT" function, which it alleges satisfies this limitation Compl. p. 15

'582 Patent Infringement Allegations

Identified Points of Contention

• Scope Questions: The central dispute is likely to be the meaning of "high-impedance voltage source." The complaint alleges that a standard 120V residential outlet qualifies as "high-impedance" relative to the vehicle's 400V system Compl. ¶49 The defense may argue that in the context of power electronics, a utility grid connection is designed to be a low-impedance source and that the term has a specific technical meaning not met by the accused use case. The complaint supports its position with a screenshot of an "AMPERAGE LIMIT" function, which allows the user to reduce current draw to as low as 8 amps, suggesting a high-impedance interaction Compl. p. 24
• Technical Questions: It raises the question of what evidence demonstrates that the accused controller modifies voltage and current "based on the monitored transfer of charging energy." The complaint alleges this occurs when charging stops at a set limit or when voltage is incrementally increased during the charging cycle Compl. ¶50

V. Key Claim Terms for Construction

"bi-directional voltage modification assembly" ('884 Patent, claim 20; '582 Patent, claim 1)

• Context and Importance: This term defines the core power electronics component that the patents claim is re-purposed for charging. The infringement case against the accused DC/DC converter rests on this term's construction.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The claims themselves use the general term "assembly," which may support an interpretation that covers any component capable of bi-directionally modifying voltage, including a DC/DC converter or a DC/AC inverter. The abstract refers to the component generally '884 Patent, abstract
  • Evidence for a Narrower Interpretation: The detailed description of the '884 patent explicitly states, "In one embodiment, bi-directional voltage modification assembly 14 is a bi-directional DC-to-AC voltage inverter" '884 Patent, col. 2:64-66 A party could argue this language, tied to a specific embodiment, suggests the inventors contemplated the main motor inverter as the assembly, potentially limiting the term's scope away from a separate DC/DC converter.

"high-impedance voltage source" ('582 Patent, claim 1)

• Context and Importance: This term is a critical limitation in the primary asserted claim of the '582 Patent. Whether a standard home electrical outlet infringes will depend entirely on how this term is construed.
• Intrinsic Evidence for Interpretation:
  • Evidence for a Broader Interpretation: The patent does not provide a specific numerical or technical definition for "high-impedance." The background section indicates the invention is for recharging from an "external energy source, such as the utility grid" '582 Patent, col. 1:40-42 This suggests the inventors intended the term to encompass common power sources, which could be interpreted as being "high-impedance" relative to the vehicle's high-voltage DC system.
  • Evidence for a Narrower Interpretation: The term "impedance" has a specific meaning in electrical engineering. A party may argue that a utility grid connection is, by design, a low-impedance source to enable efficient power transfer, and that the plain and ordinary meaning of the term to a person skilled in the art would not cover a standard outlet. The absence of a specific definition in the patent could open the door to arguments based on the term's established technical meaning.

VI. Other Allegations

Indirect Infringement

• The complaint alleges inducement to infringe for all asserted patents. The factual basis for this allegation is Defendant's creation and dissemination of "user manuals," "marketing materials," and "online instructional materials" that allegedly "specifically teach and encourage customers and other end users to use the...Accused Products in an infringing manner, including by providing instructions on how to charge" them Compl. ¶38 Compl. ¶52 Compl. ¶66 Compl. ¶80 Compl. ¶95 Compl. ¶110

Willful Infringement

• The complaint alleges willful infringement for all asserted patents, seeking enhanced damages Compl. ¶40 Compl. ¶54 Compl. ¶68 Compl. ¶82 Compl. ¶97 Compl. ¶112 The basis for this claim is alleged pre-suit knowledge of the patents and infringement, stemming from communications that began on March 3, 2025, and included the provision of detailed claim charts by Plaintiff's licensing agent on July 21, 2025, and November 13, 2025 Compl. ¶¶22-24

VII. Analyst's Conclusion: Key Questions for the Case

1. A question of definitional scope: The case will likely hinge on claim construction. Can the term "bi-directional voltage modification assembly," which the patent specification links to a DC-AC inverter, be construed to cover the accused vehicles' separate DC/DC converter? Furthermore, can a standard low-voltage "utility grid" connection be considered a "high-impedance voltage source" as required by the '582 patent, or does that term carry a more restrictive technical meaning?
2. An issue of architectural mapping: A central technical question will be whether the architecture of the accused Nissan systems-which include components labeled as an On-Board Charger, a DC/DC converter, and a battery controller-functionally and structurally aligns with the integrated, dual-use system claimed in the patents. The dispute may focus on whether Nissan's system is merely an assembly of conventional, single-purpose components or if it practices the patented method of re-purposing powertrain electronics for charging.
3. A matter of intent and damages: Given the complaint's detailed allegations of pre-suit notice, including the delivery of claim charts, a key question for the court will be whether Defendant's continued sales after receiving such notice constituted willful infringement. The resolution of this issue will be critical in determining the potential for enhanced damages.