Automotive IQ sat down with Mr. Akshay Misra Battery Management Specialist at Infineon Technologies, and discussed the biggest issues fast battery charging is facing, improvements needed in the BMS in order to handle energy demand efficiently and the future trends in battery electronics. 

• Today, what are the biggest issues fast battery charging is facing?

In principle, Lithium-ion batteries are charged by moving charged particles from a cathode to an anode; pushing those ions into the anode takes time, and forcing them in faster heats up the battery and causes efficiency losses. And if, via fast charging, you push too hard, then lithium ions may build up in metallic form on the surface of the anode, a phenomenon known as plating. This can drastically shorten a battery’s lifespan, would lead to very fast capacity degradation and safety problems such as internal short circuit, explosions, fires and leaks.

Also, as rapid charging technology is improved, it’s vital to develop a charging infrastructure. For example, there is almost no chance in the near future that real rapid charging — on the order of 2500 km/hr of charge or more — will take place when an EV is plugged in at home. The power capabilities of electrical outlets in a home simply aren’t built for the massive current needed to deliver such charges.

• In your opinion, are solid-state batteries the way to go for fast charging? Why/ why not?

Fast charging of Li-ion batteries for EV or PHEV will require battery chemistries that allow fast transport of lithium-ions in the anode, cathode and electrolyte materials.

Compared to conventional Li ion cells with a liquid electrolyte, solid state (with solid electrolytes) can potentially exhibit better ionic conductivity and electrochemical stability. Such a chemistry can also potentially exhibit improved stability and longer life compared with traditional Li ion cells under extreme cell operation conditions. Therefore owing to their enhanced safety features and higher energy density, solid state batteries would be viable option for fast charging.

The electrolyte materials still pose challenges so don't expect to see these in cars soon, but it's a step in the right direction towards safer, faster charging batteries.

• How far is the market to achieve a fully electrified vehicle? Will it be a reality by 2020?

The tipping point for electrified vehicles is in sight, and a combination of hybrid and fully electric powertrains is expected to cut the global market share of pure internal combustion engines (ICEs) by about 50% by 2030.

Major automakers have announced plans to start shifting in the direction of electrification, through either conventional gas-electric hybrids (HEVs), plug-in gas-electric hybrids (PHEVs), or pure battery electric vehicles (BEVs). As per reports, BMW is gearing up to mass produce electric cars by 2020 and will to have 12 different models by 2025. In July 2017, Volvo announced that all its models introduced in 2019 and after would be hybrid or electric.

After 2025, falling battery prices and rising consumer demand based on total cost of ownership (TCO) will drive rapidly increasing sales of all electrified vehicles, and especially BEVs. The adoption of electrified vehicles for shared mobility vehicles will accelerate because their higher mileage will result in more rapid payback of the investment.

• Adding new automated functions in the car, going through full electrification of the powertrain, or using 48V technology for hybrids have added some extra stress factors for car makers to have an optimized energy distribution through-out the vehicle. Are current battery management system solutions able to fully manage this? Or should we expect more upgrades and news in the coming years?

Currently available battery management system (BMS) solutions are able to fulfil requirements of the present. But the increased functionality of HEVs and EVs would put, however, some serious demands on the operation of modern Li-ion batteries. For example, users desire short charging times which invokes high charging currents. Consequently, this puts serious requirements on the functioning of these battery systems, especially with respect to heat generation.

Therefore in future, I expect a more precise and compact BMS IC, which could easily be integrated within a cell or a module and would be able to monitor the dynamics of each and every cell within a battery pack. The BMS IC would offer direct cell monitoring under real-time condition, store the cell history for post processing and would facilitate early failure detections. Such a BMS solution would make the entire battery system more efficient and smart.

•  What improvements are needed in the BMS in order to handle energy demand efficiently?

Current EV architecture incorporates a BMS, which is required to predict and provide each cell’s SOC and SOH, which are the most important indicators for adapting each cell’s optimized loading timely for extending the whole pack’s life. For example, in EVs, the battery SOC can be employed in the figurative sense as a replacement for the fuel gauge used in conventional vehicles. Similarly, the SOH directly relates to a battery’s performance over time.

There have been various SOC and SOH estimation methods, and each has its own merits and limitations. Therefore, in a real vehicle environment with a lot interference, the BMS should implement enhanced predictive algorithms coupled with self-learning mechanism to accurately estimate these cell performance parameter. This would increase the usability of battery pack, increase its power density and would closely track the degradation of the system performance.

Additionally, such a BMS must meet the highest safety standards, adhering to ISO 26262 and ASIL D requirements and must deliver robust EMC performance.

• What do you think will be the future trends in battery electronics?

Nowadays, scalable battery systems include huge number electronic components for the efficient monitoring, measurement and control of all safety- and customer-relevant functions. The battery electronics include the battery control unit including isolation monitoring and thermal management, power and voltage sensors, as well as cell voltage measurement and monitoring.

Deployment of PHEVs and BEVs with 400V and 800V systems, would require more accurate monitoring of cell voltage, temperature and current, requiring more electronics, complex wiring and control unit. This would make the entire system more expensive and more susceptible to reliability issues and failures. Therefore responding to varying EV application requirements, different BMS architectures would be available. Such BMS ICs could be directly placed on each cell with no/less wires and simpler controls, making the entire system more flexible and easy to integrate.

Additionally, to handle and process huge amount data of cells/modules/pack, the battery control unit would have more memory and computing power. The incoming battery data would be measured, processed, calculated, diagnosed and communicated. Based on the huge amount of battery data available, the entire BMS system including control unit would not only enhance the pack performance and but would make it more secure in different operating conditions.