Research shows that driving range and charging duration are among the most significant barriers to purchasing an electric vehicle. Charging to 80% SoC in 30 minutes does not seem to be satisfying. To make driving electric cars more convenient and reduce users' range anxiety, improving energy storage for long-distance travel is one of the highest EV traction battery development priorities.
The battery's high cost, reaching 35% to 45% of the total vehicle's cost, is a decisive factor for the manufacturers. Especially since most OEMs depend on external partners for battery cell development and production. Here, local partners with modern development and test centers are essential. The fast available, local resources can make OEMs more agile and allow them to focus on their innovations around this centerpiece of the electric car.
The technology of lithium-ion batteries:
Common to all lithium-ion batteries is that the eponymous Li+ ions move from the positive to the negative electrode during discharge.
The distinction between lithium-ion batteries is usually made based on the material of the positive electrode. Three variants are particularly relevant here for electric vehicles. The related NCA (lithium nickel cobalt aluminium oxide) and NMC (lithium nickel manganese cobalt oxide) electrodes are the most used cells in the automotive sector today. NCA cells are relatively inexpensive and have a very high energy density. The main criticism is addressing their dubious safety, as they react early and very violently in the event of overvoltage or overtemperature. NMC cells are more and generally have a longer service life, but they are also costly in comparison.
LFP cells (lithium iron [Fe] phosphate) still have a relatively small market share in the passenger car sector. However, it is a promising technology in development. LFP cells are considered very safe, have the longest lifetime of all Li-ion technologies, and are highly resilient in charge and discharge rates. On the other hand, they have an energy density that does not yet reach the level of NCA / NMC cells.
Advances in charging power, energy density and driving ranges require next-level thermal management:
The decreasing acquisition costs of an electric vehicle, primarily due to the battery's decreasing costs, make EVs more attractive for the end-customer. At the same time, combustion engines are becoming more and more expensive for OEMs due to increasing environmental policies and regulations, which makes it necessary to include hybrid and electric vehicles in their portfolio and navigate their strategy towards electrification. As a result, electric cars and hybrids have long since broken out of their niche existence and are facing a steady increase in market share, which will grow sharp over the next few years. By the mid 20s, an electric vehicle is expected to be comparable to a combustion engine car, not only regarding its purchase price but also regarding the total cost of ownership (ToC). In the future, automotive industry players and decision-makers will have to prove strong expertise to meet the market's expectations with new technologies.
Increasing the range has always been one of the main focuses of battery development. In addition to further chemical development at the cell level, the battery management system (BMS) has particular potential in this area. By closely monitoring the cells, they can be optimally loaded, allowing more capacity for the same service life. This may sound simple at first; however, reality proves it is highly complex in its practical implementation because only a few parameters can actually be measured in the battery. Important information such as the exact state of charge (SoC) or the state of health (SoH) can only be determined indirectly using complex calculation models. These are subject to ongoing research and development and must be adapted and validated again for each cell type in elaborate tests.
The BMS also plays an important role when it comes to fast charging capability. Innovative charging methods such as pulse charging can noticeably shorten charging times in certain operating states without sacrificing service life – in the future, up to 350kW charging will be possible. Therefore, charging to 80% SoC might take less than 15 mins, even with large batteries.
With this enormous charging power, the thermal management of the battery is also becoming an increasingly important factor. The charging power loss must be reliably dissipated to enable a constantly high charging/discharging performance and guarantee the battery's service life and safety. On the other hand, the battery must be heated quickly and effectively in winter to keep the range losses at cold temperatures within limits. Thus, intelligent thermal management systems can have an extreme impact on the overall efficiency of the battery, especially in cold seasons. Furthermore, since there is hardly any noteworthy usable energy loss in contrast to the combustion engine, an intelligent interconnection of the thermal systems for the battery, electric machine, power electronics, and passenger compartment makes sense.
New developments:
According to experts, the lithium-ion battery with its current technology has not yet reached the end of its development. Still, there are limits to the energy densities of battery solutions currently on the market. At present, specific energies of about 230Wh/kg are possible. Experts forecast a maximum increase to 300Wh/kg or 350Wh/kg for current technologies. For even more powerful batteries, the technology must be changed more profoundly at the cell level. Numerous companies and institutions are working at high speed on this today. A few promising technologies can be found already. The outcome is expected to be a generation of a higher energy density. Tests have shown promising results and some of them have proven to work on a laboratory scale; however, a significant challenge still lies in the economical series production.
Additionally to the profound knowledge of the drivetrain, hofer powertrain as a system supplier has built up extensive, strong know-how around battery technologies in recent years. Battery analysis, battery testing and battery development have grown into essential competence and business goals at hofer powertrain's Nürtingen location. We offer a broad spectrum of services to customers in different segments – from new concept studies, model-based simulations in design and development to agile tests on our in-house test benches, including full documentation of the analysis results and certifications.
"Never stand still" is what hofer powertrain lives by. Cooperations with universities and professors bring lively exchanges, new perspectives and constantly challenge us. We make sure that research findings are implemented quickly and efficiently for our customers.
In this light, an outstanding battery design kit hofer powertrain ULTEVATE was developed. Thanks to the modular design of standardised VDA battery modules, practically all requirements regarding size, installation space and capacity can be met. Furthermore, smaller quantities can be produced at reasonable costs. The interchangeability of the VDA modules and the cooperation of hofer powertrain with different cell manufacturers ensure great flexibility in selecting cells. Individual design preferences between high-power or high-energy batteries can be considered and special requirements regarding safety can be fulfilled. The specially developed battery management system guarantees state-of-the-art battery control and efficient integration of the thermal management into the overall vehicle aligned with the most individual requirements.
As a result, batteries can be charged to 80% SoC in only 12 minutes. This powerful high-energy battery has a capacity of 86.5kWh and is suitable for ranges of more than 500 km. Moreover, with a constant discharge power of 430kW (up to 690kW for short periods), it hardly sets any limits for the drive power of the electric motors, even in high-performance cars. Within the scope of a research project, it has proved possible to build batteries with a charging capability of up to 80% SoC in only 5 minutes and 100% in 8 minutes.
Such technological progress is made possible by our extensive testing landscape. Starting with cell characterisation, through typical electrical and thermal tests of battery modules and battery packs to endurance runs, we can map the complete spectrum of development. Our engineers can also validate and provide certification in compliance with all current standards while running environmental tests and abuse tests under appropriate safety measures.
We design individual testing procedures supporting you with a cost- and time-efficient approach to achieve project goals for specific requirements.
Exciting times for batteries lie ahead. By delivering the solutions of tomorrow today, we stay up-to-date and bring the most efficient systems to the streets. So come along and join us on our journey towards the future of battery solutions! Read more on the future possibilities and technologies in our next article.
