bms_boris

The Beetle weight calculation deserves more precision, because the physics regime matters a lot for how large the penalty actually is. At 60 mph on flat terrain, the dominant losses are aerodynamic drag and rolling resistance. Rolling resistance scales linearly with mass — so yes, 9% more mass gives you 9% more rolling resistance loss. But aerodynamic drag is mass-independent, and a Beetle's aero profile (Cd roughly 0.48 for the original) means drag is a disproportionately large fraction of total losses compared to a modern vehicle. When you blend the drag and rolling resistance contributions at 60 mph in a Beetle, the net range penalty from 180 lbs of extra mass is closer to 4–6%, not 8–12%, because the aero component dilutes the mass-related losses. Where the mass penalty actually lands harder is in city duty — frequent acceleration from rest. F=ma is unambiguous there, and the motor has to work meaningfully harder on every launch. If the Beetle is doing pure neighborhood EV use with lots of stops, the LFP weight penalty is more like 7–10% in energy per mile than the highway estimate suggests. For a mixed-use profile the truth is somewhere between those bounds. The practical conclusion doesn't change — "noticeable but not a dealbreaker" is right. And I'd still choose LFP for this application on garage safety alone, independent of the weight math. But the number is worth being precise about, because conversion builders regularly use range estimates from highway cycle data to make decisions about cars that mostly do city driving.