Industry Perspective | Enhancing the Charging Experience for Battery Electric Vehicles

After more than a century of continuous evolution, internal combustion engines have reached a remarkably high level of efficiency, performance, and reliability. As a result, drivers can typically rely on internal combustion engine vehicles to perform as expected, regardless of fuel quality or environmental conditions.

In contrast, the lithium-ion batteries that power electric vehicles are still a relatively emerging technology. Despite their rapid development, batteries have inherent limitations, such as lower energy density compared to gasoline or diesel. Therefore, maximizing the energy stored and utilized in each battery cell is crucial—this depends not only on cell design but also on the charging process. Unlike refueling an internal combustion engine vehicle, the charging experience of a battery electric vehicle (BEV) can significantly impact battery life and performance.

For an internal combustion engine, whether the ambient temperature is 10°F (-12°C) or 90°F (32°C) makes almost no difference, because hydrocarbon fuel flowing into the tank is unaffected by temperature; nor does the fuel level at the start or end of refueling matter. However, fast charging can have a significant impact on battery life, as can the temperature and state of charge at the time of plugging in.

Original equipment manufacturers (OEMs) and their battery suppliers are well aware of this and incorporate these variables into battery design, thermal management systems, and control software. This gives them confidence that the battery—covered by an 8-year/100,000-mile (161,000 km) warranty under U.S. regulations, and 10 years/150,000 miles (241,500 km) in California—will meet customer needs, avoid excessive warranty costs, and provide robust service life beyond the warranty period.

Most BEV battery management systems rely on lookup tables, resulting in a stepwise charging process that does not reach the battery's technical limits. This conservative strategy is designed to prevent harmful processes such as lithium plating, which could compromise battery life and safety.

High currents during fast charging can cause lithium deposition on the anode, reducing energy storage capacity, driving range, and battery life. This process also increases internal resistance, leading to longer charging times and degraded vehicle performance.

Severe lithium plating can form lithium dendrites; if dendrites grow large enough, they can pierce the separator, causing a short circuit, which in turn can lead to internal overheating or even thermal runaway. This issue also exists in solid-state batteries, because dendrites can pierce the solid electrolyte—which actually performs the same function as the separator.

Lookup-table-based stepwise charging curves are neither intelligent nor adaptive, and they are prone to a harmful feedback loop: the control strategy fails to account for the decline in battery health over time, thereby accelerating degradation and shortening battery life.

An alternative approach is to use physics-based charging software, replacing traditional lookup tables. This real-time closed-loop model can accurately estimate the battery's electrochemical state, actively suppress harmful processes such as lithium plating, and adjust the charging strategy based on battery health, thereby controlling degradation.

Notably, conventional charging slows down significantly when the battery is partially charged (e.g., starting from 30% or 50%). However, physics-based charging maintains a more consistent charging speed regardless of the starting state of charge—this is important because in real-world use, customers do not always plug in only when the state of charge drops to 10% (the level typically cited in product manuals as the starting point for charging). Furthermore, with physics-based charging, the system operates reliably in cold or hot conditions, whereas conventional charging strategies are significantly affected by temperature.

For consumers, physics-based charging delivers a more consistent and reliable experience and reduces range degradation over time—which is crucial for convincing skeptical EV buyers to make the switch from familiar internal combustion engine vehicles. For OEMs, it can lower warranty costs by improving battery durability. Additionally, as new regulations require disclosure of battery health and life information to consumers, it may also enhance the resale value of used EVs.

Volvo Cars has demonstrated that this system can reduce 10%-80% charging time by up to 30% without compromising energy density or range. The performance improvement is not limited to the early stage of battery life; it also maintains faster charging speeds than existing charging protocols throughout the entire battery life cycle. This metric becomes particularly important as more OEMs advertise charging performance in terms of "miles of range added in 15 minutes"—after all, a good charging experience means more time spent driving and less time spent plugged in waiting.

The battery is the most expensive component in a BEV, so extracting maximum value before the end of its life is critical for sustainability. BEVs must also provide a seamless charging experience, range, and durability so that consumers can smoothly transition from internal combustion engine vehicles.

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