A Tesla patent application published on February 19, 2026, outlines a dual-battery system for electric vehicles, including a trailer-mounted auxiliary pack. Filed in August 2024, it details integration with the primary battery via advanced management modes. The design addresses past issues with the cancelled Cybertruck range extender.
Tesla filed patent application US 2026/0048683 A1, titled “Electric Vehicle Range Extender Integration,” on August 15, 2024. It was published on February 19, 2026, and lists four inventors, including Wes Morrill, Tesla’s lead Cybertruck engineer and senior director of engineering. The system connects an 800V primary battery pack with a 400V auxiliary pack using two parallel DC/DC converters to manage voltage differences. It operates in three modes: State of Energy (SOE) Balancing, which drains both packs proportionally during driving; Open Circuit Voltage (OCV) Matching, which aligns voltages before reaching a DC fast charger; and parallel charging, enabling simultaneous charging at rates from 50 kW to over 500 kW after safety checks. The auxiliary battery can mount in a truck bed or inside a towed trailer via a high-voltage hitch interface. The trailer option includes an MC4 connector for solar panel integration and avoids consuming vehicle cargo space, unlike the bed-mounted Cybertruck extender cancelled by Tesla. Thermal management uses waste heat from converters to precondition the auxiliary pack in cold weather, supplemented by a coolant system linked to the vehicle’s main loop. Tesla had promised a Cybertruck range extender for 470+ miles in late 2023, delaying it from early 2025 to mid-2025 and reducing the range claim to 445+ miles. It was removed from the configurator in April 2025 and officially cancelled in May 2025, with refunds for deposits. The patent filing predates the cancellation, filed while the option was still offered. Rivian holds an earlier patent from 2020 on a removable battery, but Tesla’s emphasizes power management software.
