Currently reading: UK firm RML gets approval for world's highest-density EV battery

Conformity of Production approval satisfies a requirement for many big OEMs and major car makers

British firm the RML Group has been granted Conformity of Production (CoP) approval for its new VarEVolt battery, ticking a crucial box as it prepares to pitch the pack to major car makers.

It has been verified as building products compliant with safety standard UN ECE Regulation 100, a requirement for many larger OEMs and car manufacturers.

“Performance is a key part of what RML offers," said James Arkell, RML’s head of powertrain. "Doing this safely, reliably and repeatably is key to our success, and this certification solidifies that message to the industry."

The VarEVolt battery is already deployed in the Czinger 21C hybrid hypercar. It is said to be the highest-density automotive battery pack in the world, generating 6kW per kilogram and, according to RML chief Michael Mallock, is capable of “dumping all its power really, really quickly” thanks to a monumental C-rating (how quickly it can charge and discharge) of 200. The Porsche Taycan, for reference, has a C-rating of around four to five.

In the case of the Czinger’s pack, that means it can deploy its entire 4.5kWh capacity in as little as 40 seconds. It’s a characteristic that makes it well suited for deployment in a high-output plug-in hybrid powertrain.

“We’ve pivoted the powertrain team from being mainly ICE to mainly EV – battery and system integration,” Mallock told Autocar during a recent visit to the VarEVolt production facility.

Currently, output is small and matched to customer demand, but he said it can be scaled up quickly – and it won’t necessarily be limited to ultra-exclusive, low-volume propositions.

“We started doing battery design and manufacturing in-house, because there was not a supplier that could deliver what we required,” said Mallock. “Also, some of the work that we’re doing here is supporting OEMs with their next generation.”

The whole point of VarEVolt is that the system is modular and scalable, so it can be used in a variety of different applications.

RML CEO Paul Dickinson explained: “We can focus on range, we can focus on power or we can balance the two – because what we need in a PHEV is different from if you were using it in a BEV.”

Talk of future customers and partners on the VarEVolt programme was quickly shut down, but Mallock did reveal that RML was working on a conversion kit for old hybrid hypercars – think LaFerrari, McLaren P1, Porsche 918 – that could drastically increase their performance potential.

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He said: “For those types of cars, we can do a replacement pack that will significantly increase the range, and if the rest of the hardware within the car would allow it, you could have a version that was eight times the power output.”

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Charlie Martin

Charlie Martin Autocar
Title: Staff Writer

As part of Autocar’s news desk, Charlie plays a key role in the title’s coverage of new car launches and industry events. He’s also a regular contributor to its social media channels, creating content for Instagram, Tiktok, Facebook and Twitter.

Charlie joined Autocar in July 2022 after a nine-month stint as an apprentice with sister publication What Car?, during which he acquired his gold-standard NCTJ diploma with the Press Association.

He is the proud owner of a Mk4 Mazda MX-5 but still feels pangs of guilt over selling his first car, a Fiat Panda 100HP.

Felix Page

Felix Page
Title: Deputy editor

Felix is Autocar's deputy editor, responsible for leading the brand's agenda-shaping coverage across all facets of the global automotive industry - both in print and online.

He has interviewed the most powerful and widely respected people in motoring, covered the reveals and launches of today's most important cars, and broken some of the biggest automotive stories of the last few years. 

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