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Comment by jakeinspace | Hacker News Reader

3000 hp? Not sure if that's measured at the "crank" or the dynamo, but that's over 2MW, probably pushing 2.5MW of power draw from the batteries assuming a motor efficiency of 90% and some other losses. Apparently that's getting drawn at 1.2kV from the batteries, so "only" around 2kA of current draw.

That top power draw would drain the 80kWh batteries in around 2 minutes, though I'm guessing you'd hit thermal throttling or catastrophic failure before that. The batteries are allegedly rated to 30C, meaning 2 minutes to full discharge at max current.

I'm curious how the heat dissipation of EVs compares to ICE vehicles. You have much higher efficiency vs combustion and get to split the power between 4 motors instead of one engine, but you don't get the heat capacity of a massive engine block, or the convection of cold air intake + hot exhaust out the tailpipe.

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> how the heat dissipation of EVs compares to ICE vehicles

Xiaomi Su7 Ultra had a 400W twin fan, 530W liquid pump and a 28kW heat dissipation for powertrain.

28kW of dissipation is pretty solid, though obviously is irrelevant during a short burst with hundreds of watts of heat generated. I guess the frame itself act as the fallback heatsink for storing excess heat in these scenarios? Because by my math, a modest 100kg heatsink (no idea if that's reasonable) would reach 270°C in only around 45 secondw if it's trying to handle 250kW+ of heat transfer (270C is roughly the max differential for heat pipes,liquid cooling might be significantly lower limit). And obviously the batteries can't handle 270C.

2kA was pretty standard for a high end DC motor controller back 20 years ago when people were doing EV conversions with Optima Yellow Top batteries and Warp9 DC motors. Doing it at 1200V is new, though.

It's not unexpected for a record-attempt car to have severely decreased range at top speed, they're pushing up against all the limiting factors at once, hard. I seem to recall reading something about the Bugatti Veyron only having 15 minutes of tyre life at full throttle, but this not being an issue because it only carried 12 minutes worth of fuel. :)

Motor output, so you’ll still have transmission loses beyond that (but with a fixed drivetrain, with no multi-speed gearbox, quite possibly more like 95%).

I guess EVs have the acceleration and top speed crowns now, but it'll take a while for them beat any 24 hours of Le Mans records.

Only from a refueling (and battery heat) perspective though...

The majority of the lemans (or any endurance race) challenge is not from the electric drivetrain (or regenerative braking) but from the ice drivetrain and friction braking. This is reinforced by the ease that WEC and IMSA have had in implementing electric hybrid drivetrains with relative ease over the last 10 years (by most measurements making the endurance more achievable).

Yeah man, this is obviously a lie ... *yawns*

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