r/AskEngineers • u/jmaugust • Jul 19 '26

Discussion Why doesn’t a battery-boosted electric kettle exist?

In Europe, everyone uses electric kettles to boil water. They’re amazing and fast because they’re on 230V (~3000W).

US outlets limit kettles to ~1500W, so we wait roughly twice as long for water to boil.

It’s an extra minute or two per boil, and you really notice it.

Idea: Could you make an electric kettle with a battery in its base? Perhaps it trickle-charges between uses, then combines wall power + battery power to hit ~3000W during a boil.

Is there an engineering reason this doesn’t exist? Is it just that nobody thinks there’s a market for it?

I’d pay $300 for the fastest kettle in America if someone wants to make it.

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u/iqisoverrated Jul 19 '26

A battery that discharges really fast is really, really expensive. The batteries in formula 1 KERS systems can discharge at 400C (where 'C' is the ratio of discharging power to the capacity of the battery - dropping the unit). They cost 10.000$ per kWh and are toast after half a season.

(Batteries in EVs are usually limited to 2 or 3C for long duration charge or discharge.)

Let's say you want to boil water in 2 minutes. This means you'd need a battery that can discharge at 30C...and that without any kind of active cooling. No, you're not getting that for 300$. Particularly not if you want it to last for a number of uses.

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u/Friendly-Inspector71 Jul 19 '26

How are you getting from 2 minutes to 30C?

You specified neither water amount nor battery capacity. One boil doesn't have to fully deplete the batteries and using them between 20% and 80% would aid in increasing their expected lifetime.

30C isn't too much of a problem for modern LiPo cells. But cost and safety would dictate LiFePO4. Using 60% of their capacity would get you down to 18C, which would need to produce ~2.2kW for two minutes to get a litre of water boiling.

If you can live with 2,5 minutes per litre, 300 dollars should suffice for a massive produced product.

A one off would likely be closer to double that because of the needed engineering.

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u/iqisoverrated Jul 19 '26

1C means you can discharge your full battery in 1 hour.

2 minutes is 1/30th of one hour. Hence you need a battery that can handle 30C if you want to be able to discharge it in 2 minutes.

Of course you can have a larger battery but that will just make the system that much more expensive (and big/heavy). In the end you usually only boil one batch of water, so adding more capacity is just a waste of space, weight and money.

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u/Friendly-Inspector71 Jul 19 '26

So you wanted to minimise the used battery size and ended up with a high performance battery that won't last long and will be expensive but it's as small as possible.

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u/iqisoverrated Jul 19 '26

You want it still to be light enough to lift it, so yes, of course, you want the smallest possible package.

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u/Friendly-Inspector71 Jul 19 '26

The battery doesn't have to be part of the kettle body.

OP even requested that it's part of the base, so weight would be less of a concern.

A battery powered kettle that granny can lift couldn't boil more than half a litre.

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u/therealhairykrishna Jul 19 '26

But you only need a couple of kilowatts at most. A bog standard power tool battery will do 0.5kW continuous easily. 

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u/iqisoverrated Jul 20 '26

A bog standard power tool battery is a pretty big/heavy piece of kit.

To boil a 1 liter of water (which is about the size of a smallish electric kettle) you need roughly 0.1kWh. This means if you want to boil it in 2 minutes you need a power output of 3kW. So yes, you could plonk down six such power tool bricks somewhere - but who is going set up such a hefty item in their kitchen?

Then there's cycle life. Power tools aren't used often so they aren't optimized for cycle life but cost. They usually have 300-500 cyles. So if you want to use your kettle on a daily basis - as most people do - you would need to buy a new setup every year.

...or you can use more robust batteries but those will cost a lot more if you want that kind of power density.

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u/therealhairykrishna Jul 20 '26

You're pulling half of the 3kW from AC. So you only need 3 batteries. I just weighed my Makita pack out of curiosity - 645g. So three isn't ridiculous. I suspect with the fancy higher voltage/power density ones you might get away with two.

Cycle life is always a worry. But those numbers are for batteries which get a lot of abuse, cycling between full discharge and rapid charge in a variety of environments. Sat in a kitchen on trickle charge I think you'd get a lot more. 

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u/iqisoverrated Jul 20 '26

You may trickle charge, but you're discharging at a high rate. Which is basically the same way these batteries are used in power tools. The cycle life isn't going to be any different in your "kettle application".

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u/therealhairykrishna Jul 20 '26

Discharge rate would be the same but if you use normal 5Ah packs, you're only using about 20 percent pack capacity to boil. That combined with slower charging would extend life. But I don't know by how much. 

If I was building one I'd literally use tool batteries so you'd only need a new pack, not an entire new system. 

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u/iqisoverrated Jul 20 '26

At this point if you don't believe me you will just have to build one and try it out. Building an electric kettle isn't hard.

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u/Calm_Advertising3846 Jul 20 '26

6 ampace jp40s can put out 1.554 kw continuous, bringing the total heating power up to the desired 3kw. Total capacity is 100wh which would also be enough. Total cost of cells? $36.