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Comment by dahfizz | Hacker News Reader

The problem is that battery tech does not scale. To push a bigger, heavier vehicle, you need an even bigger, heavier battery. Its a diminishing returns scenario where to add a little bit more range, you need to add more battery, but the added weight of the battery all but cancels out the range that it adds.

Think of the progression. We have had electric scooters for a while already. We have just started to see electric cars going mainstream. We have seen a lot of interest in large electric vehicles like semi-trucks and commercial vans, but nothing viable yet.

EDIT: Another way of thinking about this problem: Why do Teslas have so much storage space? You could easily fill the frunk with batteries and still have competitive storage space. The reason they don't is because adding more battery really doesn't help.

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The diminishing returns argument only holds for aircraft, where the battery has to constantly work to lift its own weight.

For ground transportation, the percentage of the weight dedicated to batteries is important, but so is the ratio of wind resistance to battery power.

For low speed start and stop traffic, it is true that if your car is already 90% battery by weight, adding battery won’t help. For freeway driving, this doesn’t hold at all, since most of the energy is being lost to wind resistance.

The reason teslas have so much storage space is that air doesn’t weigh much, and the empty space helps them design for aerodynamics. Filling the space with batteries would make the vehicle too expensive.

Aerodynamic drag dominates at high speeds, but there’s a friction component that’s influenced by weight.

Accelerating more mass takes more energy. While you can recover it with regen, you can never break even.

Yes, but battery vehicles are not that much heavier as ICE vehicles and the efficiency of the electric propulsion and the benefit of regeneration works very strongly in favor of the battery vehicles. While it is not released yet, the Tesla Semi even seems to make electric propulsion work for heavy semi trailers.

I remember when the 60kWh Model S got its EPA rating - it was 208 miles vs 265 of the 85kWh version, so roughly a 11% gain in efficiency.

Bottom line: batteries do scale - at least in terms of weight.

I thought Tesla used the same physical battery pack but used software to limit how much you got.

In return you get way better battery life because there’s loads of excess capacity in the battery compared to nameplate capacity

In the very first edition that was the case only with the 40kWh version.

The 60kWh one was fairly popular and battery prices were much greater back then, so a physically different battery was justified.

Only later did the 60kWh version shrink enough in sales for Tesla to apply this trick to it.

A big empty frunk makes the car a lot safer and filling it with batteries would make it a lot more expensive.

I agree with your general point, but at the same time, the cost of batteries are getting exponentially cheaper. It's just a matter of time for all transport to be BEV, so it makes sense for companies to want to be ready for the new market realities.

s/frunk/trunk/

I don't think the price of batteries tells the whole story. Until the tech is viable, people are not going to buy an inferior car.

Most roads, at least in America, have weight limits per axle. A van or semi can only be so heavy, and having batteries take up half your cargo budget is a huge disincentive. This is on top of the severly limited range of a big, heavy, full-of-cargo EV.

frunk refers to the front trunk that Tesla's have, further increasing their caring capacity past traditional ICE cars.

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