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Comment by xwowsersx | Hacker News Reader

I don't know the EV battery space well. What is the capacity of the battery they are referring to and how does it compare to, say, the capacity of a Tesla Model S? Just trying to put this 5 minutes to 80% charge in context. As a headline, it sounds incredible. If I could charge my car to 80% in 5 minutes, I would buy an EV tomorrow, seriously.

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The capacity of an individual cell doesn't really matter, because you can linearly scale up the energy capacity and power. If you can charge a single cell to 80% in 5 minutes, then you can do the same for many cells simultaneously, as long as your power source doesn't become the bottleneck. From the perspective of battery technology, what matters is energy density, power density, and of course manufacturing cost.

But for what it's worth, the linked presentation[1] includes some test results from 2.7Ah cells, which is about the same as the capacity of a common 16850 cylindrical cell.

[1]: https://www.enovix.com/wp-content/uploads/2022/06/Ashok-Lahi...

You're also limited by your thermal management.

Running water cooling in the pack seems like a much easier issue than creating faster charging chemistry though.

Easy, at a expense of weight and volume.

Detachable/external cooling, maybe? You don't need to dissipate that much heat during normal operation.

That's just called Mechanical Engineering. All machines involve compromises. An internal combustion engine needs oodles of these kinds of compromises. It's idiotic thermal efficiency itself is a big expense if you think about it.

Yes, I'd like to see further efficient developing.

All current EVs have liquid cooled batteries already.

Exponent.energy does just that

Oh, of course. That makes sense. Thank you and thanks for the link.

There are many more variables that matter that I can think of,

How long battery holds charge

How it behave at various temperatures

How it degrades over time

How it behaves in its discharge life cycle, e.g can you drain it to 30 percent? 20? Do you have to charge it to 100?

Hence, why we havnt seen radical innovation in the battery space in the last 20 years though we see articles like this all the time.

I'm still buying lithium etfs.

To an 80% charge, all modern cars with super fast charging (Tesla Model 3/Y, Ioniq 5, etc) can do it in around 15-20 minutes assuming you're connected to the fastest charger available.

The double time to full (vs. just to 80%) is pretty comparable to other batteries though, where that remaining 20% takes almost as long as the first 80%.

So, it's a lot faster. That said, I'd be interested in lifespan. They claim 'high cycle life' but don't actually put any figures around that.

The article states that the capacity figure is just a 'goal', not something they've actually achieved... if I'm reading it right, so it's a bit meaningless at the moment.

"Enovix, based in Fremont, California, announced that it demonstrated in electric vehicle (EV) battery cells the ability to charge from 0% to 80% state-of-charge in as little as 5.2 minutes and to achieve a greater than 98% charge capacity in under 10 minutes. The cells also surpassed 1,000 cycles while retaining 93% of their capacity."

They claim is went past 1000 cycles with 93% capacity remaining.

You'd need 4x the power to charge 4x as fast though.

> That said, I'd be interested in lifespan.

Yep. I used to fly electric rc planes back when NiCads were the best battery available. Most of the cells we used were rated for a 0.1C charge and a 14 hour recharge at that rate. If you bought the right brand and model cells, it was possible to recharge them at 10C and fully charge them from total empty in just over 8 minutes. (Usually about 7 minutes with the low voltage cutoff in the speed controllers I used.)

You'd get noticeable degradation in a pack after 50 or so cycles, and some would become unusable at 100 cycles. (Which was a decent tradeoff, since a catastrophic battery destroying crash was reasonably likely to occur well within 100 flights, at least with the sort of plane and flying me and my friends engaged in...)

For a while I was flying 7 cell Sanyo AR 500mAhr packs and since I owned 3 of them I'd charge them at about 14C (7A, the highest my charger would go) which would let me relaunch every 5 mins (I'd get maybe 3.5mins of mostly full power flying time from a pack, so I'd basically fly until I got bored of landing/swapping-batteries/relaunching, or I'd crashed and broken it again.)

Kids these days with their LiPo packs and brushless motors don't know how good they have it <shakes fist at cloud>

>What is the capacity of the battery they are referring to and how does it compare to, say, the capacity of a Tesla Model S?

They are talking in terms of an individual cell that is roughly 3x30mm and saying it would have about 2x the storable energy density per cubic centimeter.

I don’t know how it compares. The source I could find lists 380Wh/kg for Tesla batteries. This article claims up to 550Wh/liter. Also sometimes they discuss the energy density of a single cell and sometimes of the whole battery.

You may buy an EV before such a battery is widely available in production.

Haha touché. I meant to say that the speed of charging is one aspect of switching to a FEV that might make me think twice about buying one, but if I could charge my car in five minutes, it'd be a much, much easier decision.

Having easy access to a charger helps a lot too. It takes only a few seconds (with practice) to plug at home or work, and you always have a charged battery. During longer trips you may have to pee or buy a coffee, and you are likely going to stop a bit more than 5 minutes. But I agree that a 5 minutes fast charging session would be nice and help people transition to EV a lot.

Fast charging is really only relevant in two scenarios:

1) You want to travel further in one go than the cars range

2) You do not have access to at home charging

For those who can charge at home, fast charging is really only needed for longer road trips. Current new cars like the Kia EV6 can fast charge at around 200 kW reliably, that means 20%-80% in around 15 minutes. For the vast majority of people this will be fast enough to be comfortable.

This generation of EVs are already very mature technology. Couple one with a 22kW home charger and you'll have very comfortable and stress free traveling.

The second point is a big issue in pretty much anywhere outside of the US. Living in houses with a private garage is not that common.

It’s not difficult to put chargers in garages for appartements complex or even in the street. It’s very common in Oslo for example.

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