BYD’s Han EV uses a DC-DC boost converter to step up battery pack voltage from approximately 400V to approximately 800V to interface with 800V HPC chargers. This design choice reduces SiC cost versus native 800V architecture, but introduces an efficiency penalty that BYD has not disclosed in any public document as of March 2026.
Three specific data points are missing: (a) boost converter efficiency curves across the full SOC and temperature range — the 3-6% efficiency loss figure cited in this audit is an engineering inference, not a BYD-published figure; (b) thermal derating thresholds — at what ambient temperature or continuous charging duration does boost power begin to derate; (c) cycle life impact of operating the boost converter at sustained high load for fleet use cases.
BYD’s commercial motivation not to publish this data is clear: the 3-6% efficiency penalty at 800V HPC chargers is the primary argument against BYD Han EV for fleet operators who have access to 800V charging infrastructure. If the efficiency penalty is at the high end (6%), the energy cost disadvantage versus a native 800V vehicle is non-trivial over a 5-year fleet operating cycle.
What would resolve it: Independent testing by a credentialled laboratory (SGS, TUV Rheinland, CATARC) measuring boost converter efficiency at 50kW, 100kW, and 150kW input across 0C, 25C, and 40C ambient temperatures. BYD could publish this within 90 days if motivated to do so. Until then, fleet procurement decisions involving BYD Han EV at 800V charging sites carry unquantified energy cost risk.
Last verified: March 2026. No efficiency curve data published by BYD or any independent source. Status: OPEN.