What is DM-i and how does BYD's plug-in hybrid system work?
DM-i is arguably the world's most sophisticated PHEV architecture. Here's how it actually works.
The architecture
Engine: 1.5 L or 1.5 T Atkinson, thermal efficiency 43.04% (world-leading for a mass-production engine).
Generator (P1) directly on the engine crankshaft.
Traction motor (P3) drives the front axle.
Battery: 8.3–26.6 kWh Blade LFP.
How it drives
0–70 km/h: Pure EV mode if battery has charge; otherwise series-hybrid (engine → generator → motor).
70+ km/h under light load: Engine can clutch in for direct drive to save the generator conversion losses.
Full throttle: Engine + battery both feed the traction motor.
Why it's efficient
Engine runs almost always at its sweet spot (2,500–3,000 rpm, wide-open throttle).
No conventional gearbox — losses eliminated.
Regenerative braking recovers energy back to the battery.
- 01Series-dominant PHEV with world-leading thermal efficiency.
- 024.5–6 L/100 km depleted; 1–2 L with daily charging.
- 03Used across BYD Seal U DM-i, Song, Qin, Han DM-i.
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