'An EV you refuel like a petrol car': is this fast-charging supermini the revolution we need?

This drivable concept car is a beautiful example of the weight spiral running in reverse. That's very good news, as the weight spiral, in its normal direction, is knocking holes in the vibrancy, efficiency and affordability of most modern cars.

You know it: more power needs a heavier cooling system, heavier transmission, heavier brakes, heavier tyres, and so heavier suspension… and so more power is needed to overcome the weight of all that paraphernalia. And round the circle you go. The same applies to battery cars when you use the obvious solution to adding range: a heavier battery demands at the very least a heavier chassis, and then you might want a stouter powertrain or an extra motor. Oh and the big battery takes more time to charge so you lose some of its range advantage anyway.

Now dream of the opposite. Shrink the battery and everything else falls around it. You get lighter suspension and tyres and brakes and a smaller motor and transmission. And a lighter body structure. Then it becomes more efficient and you can reduce the battery some more. With that, resource use tumbles delightfully downwards. Let's call it the law of returning diminishment.

With charging stations getting closer together, a smaller-capacity battery is grand in theory. Yet there's a stumbling block. Today's small batteries can't accept high charge power. So on motorway driving, where it's drag rather than weight that impacts range, you can end up with half an hour charging for every hour driving.

Which is why the car in these pictures might just exhibit the revolution we need. It is built on rapid charging as well as high efficiency and crucially low price too. Even if the critical breakthrough, the battery cooling system, is the same principle as was first used on the McLaren Speedtail and Koenigsegg Regera.

Yes this car's great leap forward, battery cooling, isn't a hugely sexy matter. But fortunately, the results are sexier than that enabler. They're summed up in the name: Triple 10.

That means first a 10-minute 10-80 rapid charging. Because efficiency, even at speed, is so good, that rapid-charge time doesn't actually mean ingesting stupendous amounts of energy. So it can be done on a common 150kWh charger. Efficiency is in fact the second of the 10s: 10km/kWh consumption – or 6.25m/kwh. That's about a third further per kWh than a comparably-sized car now.

Battery cooling isn't sexy. Fortunately, the results are

Yeah, we've had lots of stories of EVs you can recharge as fast as a petrol stop, but they demand very uncommon ultra-powerful chargers. The Triple 10 car's low consumption approaches the problem from the other direction.

Third of the 10s is lifetime CO2 emissions of 10 tonnes, assuming it's run on renewable electricity. (On present average UK grid electricity, you could add another two tonnes.) Most smallish EVs these days are 18-25 tonnes CO2 just for manufacturing, and you'd need three tonnes from average grid electricity to drive them over a lifetime. Manufacturing CO2 is closely related to price: it takes energy to mine and refine minerals and energy is costly. Less material means less energy, especially to manufacture a small battery.

Beyond diehard petrolheads, most people who don't drive EVs say that high price and slow recharging are the barriers to adoption. The Triple 10 addresses these directly. What's not to like? Provided it's a car you'd want to drive.

It stands every chance. Weight is just 1,170kg, the same as a lowish-spec Polo and less than the carbonfibre-rich BMW i3. That's propelled by a 136bhp electric motor driving the front wheels. No reason why it shouldn't feel like a lively, although not GTI-spec, supermini on the road.

Inside, there's surprising family room. It's spacious in the distance between front and back seats. Also, because the battery is small enough to go under the back seat and boot, the footwells are comfortably deep. The glasshouse tapers to cut drag – the Cd is just 0.267 and the frontal area's pretty compact too. So there are just two back seats, lightweight but comfy buckets like the front ones. Their frames are a composite using flax fibres, lightweight and renewable.

It's a simple, clean, modern cabin design, with two screens. It's a bit light on switchgear but otherwise we'd all be trying to spot where the buttons had been plundered from.

Back to the downward weight spiral. Efficiency means just 210kg of battery. Its capacity is just 31kWh net. Say it quickly so it sounds more. Hang on though. At 6.25m/kWh that's 194 miles of range. Even if, like all EVs, it does less than the quoted range when on a motorway, you could do the 300 miles of London to Newcastle or Glasgow to Birmingham with just the 10-minute stop. Is that so bad on a five-hour journey? Lots of petrol cars can't do a 300-miler without a stop.

Significantly, your charging options are extensive. Unlike exotic 800V cars with huge packs that demand 350kW chargers, or even some of the incoming 'megacharging' or 'flash charging' entrants, the Shell car needs just a 175kW job, Those, or at least the barely slower 150kW ones, are everywhere. As these stations are close together you can run the battery gauge closer to zero per cent before you stop. And you're not putting in so much electricity so you're paying less.

Right then, back to the enabler of all this, the battery. Again in pursuit of low cost, there's nothing particularly exotic about the cells. Physically they're the standard cylindrical type, and they're arranged as usual like a square of soldiers on the parade ground. In a normal battery they'd be cooled by plates, themselves water-cooled. The plates are in contact with only about 15 per cent of each cell's surface. Instead this battery is immersively cooled – that is, the cells are immersed in a bath of the coolant, giving almost complete contact with the cell surface.

You could do 300 miles with just the 10-minute stop. Is that so bad?

This vastly improved cooling is key to rapid charging. Your normal EV's battery management system detects the heat buildup in its cells and throttles back charge power after about 50 per cent. This one can keep pumping in, at or close to the full 175kW, to a much higher state of charge.

Obviously this would be impossible with a water-based coolant because the immersed cells would short out. The liquid used here is dialectric, or insulating. In other words you could be having a bath in this stuff, and if your intending murderer dropped a live hairdryer in there, you'd be fine. Although, disclaimer, TopGear.com can't vouch for the dermatological effects of the fluid itself. It's hardly tea tree and lemongrass bubble bath.

Shell says you can add 90 per cent more range for every minute on the charger than a conventional EV at the same post. Also, because each cell is cooled more uniformly both within itself and versus its neighbours, the process is less harmful.

The battery was actually developed for the car by race specialists RML, and they've already designed an immersively cooled pack, with slightly different cell chemistry, for a hypercar – can't say which, NDA, bah blah. RML thinks it'll become more widespread, as PHEVs in particular demand power-dense rather than energy-dense batteries. Power density is the aim with the Shell car (in and out of the battery), as well as low cost per kWh.

The coolant used here, although oil-based, is about the same viscosity as water, and so having settled on the battery cooling, the engineering team had another brainwave. Instead of having a separate water-based circuit, with separate radiator and pumps, for the motor and high-voltage electronics and charger, and another for the cabin climate system, those too use the same dialectric fluid. They're in one circuit using off-the-shelf parts. Simpler, lighter and cheaper. Automatic valves will shut off various parts of the circuit when not needed, so for example the battery warms quickly from a cold start.

By the way, when it's charging, there's enough thermal inertia in the fluid that usually it'll just heat that up during the charge event, rather than calling on energy-draining pumps and fans. Then the radiator cools the fluid down again when you drive off, thanks to air now naturally passing through the radiator.

There's serious design and engineering heft behind it

The Triple 10 Challenge car might be a lightweight but there's serious design and engineering heft behind it. Initial work in the shape and the frame was by the Gordon Murray Group, race engineers RML did the battery work, British manufacturer Empel did the motor, and Horiba MIRA did the chassis, and the whole car's validation and testing. It might seem odd that the impetus comes from Shell, an oil company, but it's the lubricants and coolants division of Shell at work here, not the fuel division.

This isn't like a manufacturer concept that's an unsubtle hint of a coming road car. It's a tech demonstrator and no direct descendant will go on sale. But critically it doesn't depend on moonshot manufacturing or materials. It's an elegant combination of available technologies for a new result. It doesn't look or feel futuristic.

Instead it addresses what a lot of car buyers need right now. A cheap usable car that replenishes fast when you can't charge at home. An EV that you refuel like a petrol car.