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Comment by baddox | Hacker News Reader

All these EVs use roughly the same small cells, right? Essentially thousands of the same cells used in hobbyist RC aircraft (with which I’m fairly familiar)?

Unless I’m mistaken, each little cell should theoretically be chargeable in parallel, limited only by heat, massively parallel wiring, and the one massive input carrying ridiculous current.

In theory, if one cell takes 30 minutes to charge, all cells could be charged in parallel in 30 minutes. Obviously this is ignoring the challenges I mentioned, which generally don’t apply to the relatively small RC aircraft with which I have experience.

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If all of them are connected in parallel, then you are right. It's like filling an array of glasses in the rain.

However the superchargers connect to the vehicle through a power port, which is relatively small. So it may not have as many parallel connections. You could split the charging to individual cells inside the car, allowing for parallel charging of all the cells simultaneously, but that means that the supercharger has to handle the cumulative power requirement of all the cells in parallel. So if you have 500 50W cells, then the super charger has to have the capacity to handle 25 kW of power. And that much power requires some very bulky cabling, even with a 3-phase supply.

The parallel connections are visible: https://insideevs.com/wp-content/uploads/2017/12/Tesla-Semi-...

Yup, definitely 3 phase. But then it has to supply a charger or an array of chargers on the vehicle that convert the power to DC, leading to increased bulk and costs. So we're back to the 501 terminal plug again.

Perhaps they’re looking into some even superer superchargers for the tractors. It’s a shame they apparently publicly abandoned the hot-swap battery system, although I can’t imagine they’re not still working on it, especially for the tractors.

You'd still have to transfer the heat from the cells inside the battery. That would probably lead to a design with increased battery surface, maybe even a radiator or cooling lines.

Already what happens. GM and Tesla use pumped liquid glycol for heating/cooling and some other companies use refrigerants.

Interesting. I did not know that. I always figured they must need to manage heat, at the bare minimum by preventing huge draw for extended periods of time. Do you know where they radiate the heat, given that most Teslas don’t (to my eyes) have visible grill vents?

You only need to do that when charging the battery.

Oh, do the batteries not heat up when discharging quickly as well? I know next to nothing about battery chemistry, but for some reason I just intuitively assumed they did. RC aircraft batteries can certainly catch fire if something causes them to discharge extremely quickly.

They discharge slowly during driving, unless you floor the acceleration while driving up a slope, but I'm sure there are some kind of limits in place, to prevent the user from draining an unsafe amount of power from the battery.

All Teslas have a grill in the front, it's down low. The battery cooling system is shared with the cabin cooling system.

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