EV charging speed remains one of the factors influencing business and consumer acceptance.

Sally Bailey, UK head of EVC at Vestel Mobility, examines today’s charge speeds, the challenges of overcoming the bottleneck and the promising future of faster EV charging for fleet managers and end users alike.

While the case for consumer and business fleet EVs gets ever stronger, time spent charging, particularly for business journeys, remains a point of contention. Employee downtime is a real concern for trades, and time-pressed consumers don’t want to factor in lengthy charging stops on long journeys for holidays or visiting friends and relatives.

Unlike a simple ICE fuel fill, EV charging speed is influenced by a significant number of factors, including the type of charger, local grid infrastructure, the car’s software, battery chemistry and age, time of day and even the weather. Technology is addressing some of these issues, some can be worked around, and others, such as a freezing cold Monday morning, are just a fact of UK life.

EV batteries operate on direct current (DC), necessitating conversion when using alternating current (AC) chargers from the UK’s AC grid supply. Plugged into a typical residential AC charger, the onboard charger (OBC) in the EV handles the AC power to DC conversion. That inherently limits charging speeds based on its conversion capacity, typically between 7kW and 22kW. The efficiency of this conversion process significantly impacts charging duration, with losses typically manifesting as heat within the onboard electronics. For overnight charging, these speeds are acceptable, charging most EVs before the user heads off to work the next day.

Conversely, DC chargers bypass the OBC by supplying power directly to the battery, allowing significantly higher charge rates. This difference in architecture dramatically affects the practicality and speed of charging, enabling quicker refuelling suitable for long-distance travel and high-demand scenarios such as commercial vehicles.

A motorway service station offering 100kW DC power will put 50-80% charge on most EVs in the time it takes to use the facilities and visit the coffee shop (30-60mins). The increasing number of ultra-rapid DC units with a capacity of 150kW and above can significantly reduce charge and work downtime; however, several other factors also come into play.

Not too hot, not too cold

Specific charging temperatures are crucial to the electrochemical processes within lithium-ion batteries, so extremely cold or extremely hot weather has a dramatic impact on charge speed. Charging involves the migration of lithium ions from the cathode to the anode through an electrolyte. In low temperatures, typically below 5°C, the electrolyte viscosity increases, reducing the mobility of the ions and slowing chemical reactions and charging rates. This necessitates battery warming strategies implemented by many modern EVs, such as integrated heating elements or preconditioning routines, before fast charging commences.

Conversely, at high temperatures (above approximately 35°C), increased chemical reaction rates pose a risk of rapid electrolyte decomposition and accelerated cathode degradation. Heat-induced side reactions, including the formation of the solid-electrolyte interphase (SEI), can lead to permanent capacity loss, reducing the battery’s effective lifespan. Battery management systems (BMS) in cars and charging infrastructure actively reduce charging currents to mitigate thermal build-up, again slowing the charging process.

Sophisticated liquid-cooling or air-cooling mechanisms for the battery, alongside predictive algorithms that maintain optimal temperature ranges and enhance overall battery efficiency, are continually improving. No surprise, then, that each subsequent generation of EVs charges faster, more efficiently and offers ever-longer battery life.

How to avoid charging gridlock

Grid supply limitations to the charging area will significantly impact charge speed, particularly when multiple high-speed or ultra-rapid chargers are deployed and used simultaneously, such as at peak times at busy motorway services.

Load balancing is crucial in these locations to prevent overload on the local grid, which could lead to voltage instability or infrastructure damage. Most modern EV chargers, as well as all clustered DC locations, have intelligent load-balancing systems that dynamically allocate power among chargers. This adjusts charging speeds in real-time based on instantaneous demand and available grid capacity.

Load balancing architecture ensures stable and efficient energy distribution without compromising infrastructure integrity or causing power bottlenecks, but inevitably results in slower charge speeds at peak times in busy charge areas. Network upgrades are underway in many areas of the UK for this very reason. For the remotest locations, battery energy storage systems (BESS) can also alleviate instantaneous pressures on the local grid.

The final factor influencing charge speed is the EV’s charging profile and BMS. EVs typically exhibit non-linear charging profiles, deliberately reducing charging rates above approximately 80% state-of-charge (SoC). This reduces thermal stress on the battery, safeguarding its longevity and operational safety. Ongoing research continues to refine charging algorithms to balance charge speed, energy efficiency and battery durability.

Future developments

Technological innovations continue to optimise EV charging solutions. Advanced silicon-based anodes, solid-state battery technologies and more sophisticated thermal management systems promise substantial improvements in charging speeds, battery longevity and operational temperature flexibility.

Infrastructure advancements, including the proliferation of ultra-rapid DC chargers and enhanced load management algorithms, will further alleviate geographical charging bottlenecks. Integrating renewable energy sources and local energy storage solutions into charging networks, along with smart-grid predictive analytics, will also play a crucial role in supporting the growth of scalable, sustainable EV infrastructure.

While EV charging speed may appear straightforward from an EV brochure, its underlying technical intricacies, encompassing chemistry, thermal dynamics, grid interaction and battery management, remain critical to achieving real-world charging speeds in practice. Workarounds, such as modifying user charge times, switching charging locations and selecting the correct charger on the route, remain a factor of successfully owning an EV or running a business fleet of them.

The good news is that all these areas are being researched and developed by major players across the energy and EV industries, including Vestel Mobility, ensuring that EV charging speeds will continue to improve quickly as the EV sector evolves.