The rapid expansion of electric mobility creates a large and distributed storage potential that can support the power grid through bidirectional charging. However, using vehicle batteries for grid services introduces additional charging and discharging cycles, which can accelerate battery ageing and reduce the useful lifetime of the traction battery. This challenge becomes more critical because battery packs consist of many cells and modules that may age differently over time, so the degradation of individual weak cells can limit the performance of the entire system. Conventional charging architectures and battery management systems offer only limited flexibility to control these effects at module level. Therefore, a new battery-friendly charging and control concept is required to make bidirectional charging technically feasible, economically attractive, and sustainable over the full battery lifecycle. 
 

MultiLOAD addresses this challenge by developing a vehicle-side charging architecture based on a Modular Multilevel Converter (MMC) topology. In this architecture, battery modules can be dynamically connected, bypassed, or selectively loaded during operation, creating additional degrees of freedom for controlling power flow and battery stress. The project combines this modular power-electronic structure with an advanced BMS and model predictive control (MPC), allowing charging and discharging profiles to be distributed according to the current state of charge, state of health (SOH), temperature, and operating requirements of the battery modules. By decomposing bidirectional charging profiles into suitable microcycles and assigning them intelligently across the modules, the system aims to reduce cyclic ageing while maintaining the required grid-service performance. This approach also enables active balancing without additional hardware and can simplify the vehicle charging architecture by integrating functions that are usually handled by separate components.
 

The main goal of MultiLOAD is to develop and demonstrate a resource-saving battery management concept for bidirectional charging in electric vehicles. The project aims to design and prototype an MMC-based charging architecture together with a BDL-capable battery management system. It will experimentally investigate how pulse-power charging and microcycles influence lithium-ion cell ageing and use these findings to develop adaptive, modular operating strategies. A key objective is to control battery modules in a SOC- and SOH-dependent way, so that healthier modules can be used more intensively while weaker modules are protected, enabling software-based SOH balancing. Finally, the concept will be validated through simulation, model-based development, HiL/Power-HiL testing, and representative grid-supportive bidirectional charging profiles. 
 

• Modular Multilevel Converter
• Battery Ageing
• SOH Balancing
• Model Predictive Control
• Battery Management System
   

January 2024 - December 2026

• RPTU Kaiserslautern 
• Capgemini Deutschland / ALTRAN Deutschland S.A.S. und CoKG 
• STABL Energy GmbH
• BIT GmbH – Berliner Institut für Technologietransfer
• AKKA Industry Consulting GmbH

Prof. Dr.-Ing. Naim Bajcinca
Gottlieb-Daimler-Str. 42
67663, Kaiserslautern
+49 (0)631/205-3230
naim.bajcinca(at)mv.uni-kl.de