Electric-vehicle batteries often lose usable capacity because one weak cell restricts the whole pack. Researchers at Chalmers University of Technology now present a system-level answer: reconfigurable battery packs that can bypass problem cells. Under favorable conditions, the modeled architecture extends battery lifetime by more than 20 percent. It can also delay replacement and preserve more residual value.
Why One Weak Cell Limits a Pack
A conventional EV battery pack contains many lithium-ion cells connected in series and parallel. These cells do not age at the same rate. Manufacturing differences, temperature exposure, charging patterns, and usage all create cell-to-cell variation.
In a fixed-configuration pack, the weakest cell becomes the bottleneck. The pack must operate within the limits of that cell, even when neighboring cells retain substantial capacity. Chalmers researcher Albert Škegro compares the arrangement to cells tied together by a rope. They must move at the pace of the slowest cell and stop when it stops.
This structural constraint is not a minor issue. The research team describes cell-to-cell variability and premature failure as core inefficiencies of conventional fixed-configuration packs. Consequently, a pack can be retired while much of its stored energy remains technically usable.
What Reconfigurable Battery Packs Do
Reconfigurable battery packs, or RBPs, change the electrical connections between cells during operation. Switches and control electronics allow the battery management system to isolate or reconnect individual cells or cell groups. As a result, the pack can route current around a cell that begins to limit performance.
The concept goes beyond conventional cell balancing. Balancing typically adjusts charge levels between cells. Reconfiguration instead alters the pack topology itself. It can disconnect a weak cell, redistribute current, and continue using the healthier portion of the battery.
Chalmers describes this as a spectrum rather than a simple on-or-off choice. The most advanced model gives every cell its own controllable switch. More practical designs control groups of cells together. The level of granularity determines how much benefit a manufacturer can achieve.
Key Functions of the Architecture
- Isolate a weak or fault-affected cell from the active current path.
- Use more of the remaining capacity in healthy cells.
- Adapt the pack configuration as cells age differently.
- Support safer operation by managing problematic cells.
- Potentially improve charging behavior through more flexible current routing.
Modeled Lifetime Gains Exceed 20 Percent
The study, System-level assessment of dynamic reconfiguration for lifetime and cost outcomes in electric vehicle battery packs, was published in Nature Communications. It was led by Chalmers and carried out with PHINIA and Scania. The authors include Albert Škegro, Torsten Wik, Bo Bijlenga, Alexander Bessman, and Changfu Zou.
The researchers built a battery-technology-agnostic evaluation framework. It combines detailed cell models with statistical analysis across different designs, chemistries, pack voltages, thermal conditions, and usage profiles. They then assessed 20 representative EV models from 15 manufacturers.
In the most fine-grained and idealized case, reconfiguration extends lifetime by more than 20 percent. The largest gains appear in high-voltage vehicles with many series-connected cells. Electric trucks and long-range passenger cars fall into this category.
However, the headline figure is an upper limit. Real vehicles are more likely to control cells in groups rather than individually. Therefore, the realized benefit will depend on the chosen hardware architecture, control strategy, and cost constraints.
Replacement Could Move From 10 to 11 Years
To translate the modeling into practical terms, the team examined an 80 kWh passenger-car battery. The example assumes 12,000 kilometers of annual driving. It also assumes that a conventional pack is replaced after 10 years, reflecting current industry practice.
In the model, the reconfigurable pack reaches the same replacement threshold after about 11 years. That is roughly 14 months of additional service life. The pack also retains a higher residual value because it has aged less by the time of replacement.
This matters for private owners because battery replacement remains one of the largest potential ownership costs. It matters even more for fleets. A fleet with hundreds of packs could reduce replacement frequency, downtime, and lifecycle expenditure.
The Economics Depend on Design Choices
The added switches, sensors, wiring, and control software increase upfront cost. The researchers do not present reconfiguration as universally profitable. Instead, they identify conditions under which longer service life and higher residual value can outweigh the initial investment.
Their sensitivity analysis identifies several economic thresholds. Reconfigurable packs are more likely to be viable when battery capacity exceeds about 50 kWh. They also perform better when annual driving distance stays below 12,150 kilometers. In addition, the added upfront cost needs to remain below 7.16 percent.
These thresholds are important for vehicle manufacturers. They suggest that the technology may first suit larger, higher-voltage, long-range platforms. Smaller city cars with modest battery capacities may face a weaker business case.
Factors That Shape Commercial Viability
- Pack voltage and the number of series-connected cells.
- Battery capacity and vehicle range.
- Annual distance traveled and duty cycle.
- Cost of switches, sensing, wiring, and control hardware.
- Complexity of the battery management system.
- Expected lifetime extension and residual-value improvement.
Engineering Trade-Offs Remain
Reconfiguration offers clear functional advantages, but it also introduces engineering challenges. More switches increase conduction losses. Additional components add weight, cost, and potential failure points. The control system must also make fast, reliable decisions about cell isolation and reconnection.
Chalmers frames these issues as lower-level barriers that designers must manage to reach higher-level benefits. Those benefits include longer lifetime, improved safety, and faster charging. The trade-off is therefore architectural as well as economic.
The researchers emphasize that reconfiguration is not a replacement for good cell design or thermal management. Rather, it is an additional layer of system intelligence. It allows the pack to respond to variation that inevitably emerges during real-world operation.
Potential Sustainability Benefits
Longer battery life has a direct sustainability value. A pack removed from service prematurely wastes embodied materials and stored energy. Extending its useful life reduces the need for new cells and postpones recycling or disposal.
The architecture could also change manufacturing practices. Today, producers invest heavily in testing and matching cells with similar characteristics. Reconfigurable packs tolerate greater cell variation because weak cells can be bypassed. This may reduce the need for extremely tight cell matching.
Second-life applications add another opportunity. A pack retired from vehicle duty may still have enough capacity for stationary energy storage. Because reconfiguration can preserve more usable capacity, more packs could become suitable for a second service life.
From Research Models to Production Vehicles
The technology is not yet available in series-produced or mass-produced vehicles. However, it has been tested in research and industrial prototypes. The study was conducted with industry partners PHINIA and Scania, indicating active interest from automotive and powertrain suppliers.
Chalmers has also built earlier work in this field. A 2023 conference paper by Škegro, Zou, and Wik examined potential lifetime extension through dynamic battery reconfiguration. A later Chalmers project developed a unified mathematical modeling framework for reconfigurable systems at cell, bank, and pack level.
That earlier framework uses logic-gate mappings to represent switch operation. It models state of charge, voltage, and current distribution across individual cells under different scenarios. This modeling foundation helps designers evaluate configurations before building complex hardware.
What It Means for EV Makers
For automakers, the research provides a quantitative basis for architecture decisions. It suggests that dynamic reconfiguration could become a scalable option for next-generation battery platforms. The strongest case appears in high-voltage packs, long-range vehicles, and commercial fleets.
For battery-management developers, the work shifts attention toward system-level control. Software must detect weakening cells, estimate their condition, and reconfigure the pack without compromising safety or performance. This makes the battery management system more central to pack value.
For suppliers, the findings create a potential market for intelligent switching hardware, advanced contactors, sensing systems, and control electronics. The opportunity is not simply to add components. It is to deliver reliability and control at a cost that supports the economic threshold identified by Chalmers.
Important Caveats
The 20 percent figure should not be read as a universal guarantee. It comes from modeling under optimal and highly granular conditions. Practical implementations will likely deliver smaller gains because cells will be controlled in groups.
The economic case also depends on real hardware costs, which are not yet established at mass-production scale. Reliability of switches, thermal performance, electromagnetic compatibility, and software safety will all influence deployment.
Still, the study is notable because it evaluates the concept across many vehicle types and operating conditions. It does not rely on a single laboratory case. Instead, it connects cell-level behavior to pack lifetime, replacement timing, residual value, and total cost.
Why This Research Matters
EV battery packs are expensive, material-intensive, and central to vehicle value. Any architecture that extends service life can improve ownership economics and reduce resource consumption. Reconfigurable packs offer a route to use batteries more fully before replacement.
The Chalmers work does not claim that weak cells disappear. Instead, it shows that their impact can be contained. A pack no longer needs to be governed by its least capable cell.
If manufacturers can implement the concept at acceptable cost, battery replacement could be delayed, residual values could rise, and more packs could enter second-life storage. Those outcomes would make reconfigurable battery architecture a significant candidate for future EV platforms.
Sources: Chalmers
