The tech new Mercedes CLA is using to crack EV efficiency
When Mercedes-Benz first showed the Concept CLA in 2023, it coined the phrase “the one-litre car of the electric age”, highlighting the lengths it was going to in achieving 93% efficiency between the battery and the driving wheels.
The new CLA EV is due later this year, and with a potential range of 466 miles it will consume energy at a rate of 12kWh every 62 miles, or more than five miles for a single kWh. On the UK’s cheapest domestic energy tariffs, that would equate to about 1.3p per mile for fuel.
To achieve that, Mercedes is using every trick in the electric car book, with a drive system based on the Vision EQXX concept’s technology.
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The basic CLA EV will have a single rear motor with a two-speed reduction transmission.
Although more than one speed isn’t essential for a motor, some manufacturers opt for them on at least one axle. In this case, Mercedes argues the short (11:1) first gear gives better initial acceleration than a single fixed ratio, along with improved towing capacity and superior efficiency in urban traffic.
The second ratio (5:1) improves efficiency at motorway speeds, and shift points are decided by software to eke out maximum efficiency in any given situation, the selected driving programme and battery state of charge.
The first gear is selected by a mechanical dog or ‘claw’ engagement and the second by a plated clutch, and shifts are claimed to be indiscernible.
The 268bhp motor is of the permanent magnet type (used by most EVs for its high efficiency and performance), but Mercedes claims the rare-earth content of the magnets is so small as to be insignificant.
Said to be “remarkably quiet”, it has the latest hairpin windings and its magnets inserted into the rotor in a ‘double-V’ (as if one on top of the other). The idea is to concentrate the magnetic flux, improving torque density compared with other methods.
The inverter is based on silicon-carbide chips – a premium technology that has been steadily introduced over the past few years for its high efficiency.4Matic models will have an additional single-speed 107bhp drive unit on the front axle to give four-wheel drive when it’s needed.
To avoid energy-sapping drag from the motor and its transmission, there’s a mechanical disconnect unit, much like in many ICE cars’ 4WD systems.
The front motor has its own silicon-carbide inverter and both the front and rear motors can perform regenerative braking.
Despite being billed as an entry-level EV, the battery and electrical architecture runs at 800V so the battery can be charged at 320kW. This was claimed to enable the Concept CLA to gain 186 miles of range in 10 minutes.
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