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Comment by nine_k | Hacker News Reader

> Donut Lab’s all-solid-state battery delivers 400 Wh/kg of energy density

This is damn impressive. I suppose all the makers of military drones are lining up at the factory already. I mean, electric bikes are fine, but who has the most burning need to increase range and payload?..

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i don't see them mentioning of price and C-rating. Suppose their C-rating is sufficient. Current widely available cheap batteries are almost 300Wh/kg. So, on a 3 kg drone with up to 3 kg payload (say RPG-7 single shaped charge warhead) with say 30 min flight time the new battery will give you 10 min additional flight time. At what price? If the price results in having only one 40 min drone instead of 2 30 min drones, then in the current war, only say 10% drones would need to be with new batteries, while it would be most effective to have the rest with the old batteries as the current war seems to be about horizontal scaling.

Overall - their page sounds like a revolution in battery industry as they hit all the points - durability, capacity/weight, fast charging, etc. It is like Musk should just close his GigaFactory. I mean, i would like such a revolutionary development as in particular it would mean we'll soon get personal VTOLs (where price aspect is less important than in the case of drones mentioned above) ...

Yeah, I was noticing that too. There is a company out there, Amprius, which has validated their silicon anode lithium ion batteries that can discharge at 10C (or 20C pulses), have varying densities from ~345wh/kg to 450wh/kg, and are shipping them to customers for drones and VTOLs.

I think until we have an independent lab verify the results, it's pretty much impossible to say if their (Donut Labs) claims are true or not. The only thing I'm particularly suspicious of is that they claim their battery was verified but didn't say by who or provide a whitepaper on it. Both of those seem to be the bare minimum for most battery manufacturers, and with their extraordinary claims I'd assume they'd have them front and center.

I agree, but I suppose most batteries in circulation at the front lines are not fresh, and likely have 75%-90% of the original capacity after intense discharge-charge cycles multiple times a day. If his battery does not deteriorate as quickly, it may be worth the price, for non-kamikaze-type drones. Not a shaped charge and ramming into armor, but a mortar round dropped from 300-500m, undetected. There is a ton of videos on YouTube with footage from such bomber drones.

10 extra minutes may mean extra 5 kilometers of range, or of a patrol / recon route.

Also you really don't need 1000s of cycles in military drones, so maybe some more "crazy" chemistries can be used.

If the drone can fly 10 times it's probably good enough.

It depends; not all drones are kamikaze-type. Great many drones are used for delivery (food, ammo, medkits), for reconnaissance, as carriers of smaller drones, and as radio retransmitters. Bomber drones also fly a large number of sorties before getting shot down or breaking down from wear.

Ground teams usually have a bunch of batteries for quick replacement, because charging is slow. With these fast-charging batteries, they may need to lug fewer batteries, and larger generators.

I've looked at the stats, and it's:

- 45 flights per recon consumer quadcopter drone before it's lost

- 69 flights per heavy bomber drone before it's lost

They switch the batteries before each flight anyway, so even batteries that are rated for 10 cycles would be good enough if the price/performance is good enough.

Certainly batteries rated for 300 cycles are an overkill.

Source (from March 2025): https://www.forbes.com/sites/davidhambling/2025/04/16/hidden...

Also I'm listening to Piotr Ryczek talking about his time with drone unit in Ukraine, and he says recovering drones is complicated (because you have to land far away from your position and the enemy drones wait for people trying to recover a drone that landed, so you have to wait for hours before going there and do it at night). Which drains the batteries to 0 after every flight and reduces the drone availability by half or more.

So there's tactical reasons not to focus on quality too much, too.

It's less about cycles and more about the energy density per kg. Nothing on the market comes close to 400Wh/kg.

The same technology for defence purposes is available from here: https://esoxgroup.com/

You can already buy Amprius's silicon anode cells at over 400wh/kg.. but they have low cycle life.

Sorry to hijavk, but why are drones still on electric power? I'd expect some kind of air breathing engine to be manufacturable at low cost if it only has to function for a single flight. Especially for interceptor drones the speed is valuable. But for all types of drones the extra range is also highly valuable.

This could arguably be a huge contribution by EU to Ukrainian war aid, given the batteries are manufactured in Finland.

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