Ford's published application US20250033499A1 (published January 30, 2025, as an A1) is classified under B60L 53/22 (charging with inverter/converter), B60L 58/27 (battery temperature control), H02P 27/08 (PWM inverter control), and the H01M 10/615/625/637 cell-heating classes. As a published application the claims are pending, not granted. The proposed invention is a way to warm a cold traction battery using the vehicle's own inverter and motor as the heater — no separate resistive heating element — by exploiting a circuit topology most EVs already have most of.

“A system for an electrified vehicle, such as a battery electric vehicle (BEV), includes an inverter connected between a battery and a motor having windings.”— U.S. Patent Application 2025/0033499 A1 source

Independent claim 1 states the whole mechanism: "an inverter connected between a battery and a motor having windings; a center-tap of the battery and a neutral-point of the windings being connected whereby the battery, the inverter, and the motor are connected in a closed circuit; and a controller configured to control the inverter to cause a circulating current from the battery through the closed circuit to thereby achieve a target temperature of the battery." The key structural move is connecting the battery's center-tap to the motor-winding neutral point. That ties the three-phase windings' star point back to a midpoint of the pack, completing a loop through which the inverter can push a current that goes nowhere useful mechanically but dissipates resistively — heating the pack from its own internal resistance and the windings, rather than spinning the rotor.

The thermodynamics here is the point: a cold lithium pack has high internal resistance and cannot accept fast charge or deliver full power until warmed. Conventional designs add a dedicated heater; this application instead drives a "circulating current" through the battery-inverter-motor loop so that the pack's own I²R losses raise its temperature. Claim 4 specifies that "the circulating current is an alternating current (AC) square wave," and claims 2 and 3 give the controller authority over "an amplitude of the circulating current" and "a frequency of the circulating current" — so heating rate is tuned by how hard and how fast the square wave is driven, not by a separate component.

The switch dependents are what make the scheme practical, because you cannot leave that center-tap-to-neutral connection closed during normal driving. Claim 5 adds "a conductor having a switch movable between an opened position and a closed position," with the center-tap and neutral "connected via the conductor when the switch is closed" and "disconnected when the switch is opened." Claim 6 puts the switch under controller command. Claims 7 and 8 establish the two normal modes when the switch is open: the inverter "drive[s] the motor with electrical power from the battery" (propulsion) and "suppl[ies] the battery with electrical power received via the motor" (regeneration). So the same inverter and motor do three jobs — propel, regenerate, and self-heat — with a single switch selecting whether the heating loop is engaged.

Claims 9 and 10 detail the pack split that the center-tap implies: "the battery includes a top battery bank and a bottom battery bank; and a cathode of the top battery pack and an anode of the bottom battery pack are connected together at the center-tap," with claim 10 requiring "a voltage of the top battery bank and a voltage of the bottom battery bank [be] substantially the same." A symmetric split pack with an accessible midpoint is the structural prerequisite for the whole approach, and claiming it explicitly fences the topology.

The method claims add the operating discipline that keeps this safe. Claim 11 restates the loop and the circulating-current control as a method. Claim 14 is the important guard: connecting the center-tap and neutral "is performed only while the vehicle is not being propelled by the motor and the target temperature of the traction battery is not achieved" — heating only at standstill and only until warm. Claim 15 requires disconnecting before propulsion and reverting the inverter to driving the motor. Independent claim 16 re-casts the system with the switch and adds a useful extra benefit: the circulating current generates heat "for warming the traction battery and transmission fluid of the motor," extending the self-heat to the gearbox lubricant. Claims 17–20 repeat amplitude/frequency control, the square-wave form, and the standstill-only switching discipline in apparatus form.

The CPC stack maps cleanly onto the claim's two halves and explains the hedge in a pending set. B60L 58/27 (battery temperature control) and the H01M 10/615/625/637 cell-heating classes cover the objective — warming the pack — while B60L 53/22 (charging with inverter/converter) and H02P 27/08 (PWM inverter control) cover the means, the inverter driving the circulating current. What the classification cannot convey is the economy of the idea: the inverter and motor that already exist for propulsion and regeneration are repurposed as a heater, so the design removes a dedicated heating element and its cost, weight, and packaging. The standstill-only guard of claim 14 is the limitation that makes that reuse safe — heating is permitted "only while the vehicle is not being propelled" and only "until the target temperature... is achieved," after which claim 15 forces the switch open and returns the inverter to driving the motor. That discipline is what keeps the self-heat mode from interfering with traction, and it is the kind of operational limitation that often survives examination even when a broad apparatus claim narrows. The square-wave control of claim 4 and the amplitude/frequency authority of claims 2 and 3 give the controller a clean way to dose the heating power, and claim 16's extension to "transmission fluid of the motor" shows Ford reaching for the gearbox-lubricant benefit in the same loop.

The verdict: a clean, mechanism-specific application — but pending, so scope is proposed, not examined. The distinctive limitations are the center-tap-to-neutral closed loop and the controller-driven AC square-wave circulating current, with the single switch (claims 5–6) and the standstill-only guard (claim 14) making it deployable, and the transmission-fluid warming (claim 16) widening the benefit. The likeliest examination pressure is on how broadly claim 1's bare "closed circuit... circulating current" can stand over existing motor-as-heater art; the patentable weight may settle into the switch, the square-wave control, and the symmetric-split-pack topology. Report it as a proposed inverter/motor self-heating claim, flag the application status, and read the substance in the center-tap-neutral loop rather than in the abstract's general "achieve a target temperature" phrasing.