The Evolution of Electric Vehicle Batteries: Porsche’s Approach to Longevity and Safety
Electric vehicle batteries are akin to the lifeblood of the car, and at Porsche, they are crafted to last as long as traditional combustion engines—at least 15 years or 300,000 kilometers.
The natural degradation of a battery is unavoidable, yet it can be managed. In the initial months, a lithium-ion battery may lose between one and five percent of its capacity, a phenomenon known as the ‘initial drop.’ Porsche engineers consider this by designing their batteries to have a slightly higher initial energy content, slowing the effective state of health (SoH) decline.
Critical factors affecting battery aging include temperature, charge state, and charging current. Ideally, batteries should be kept below 30 degrees Celsius and charged to under 90 percent when parked for long durations. Porsche’s patented fast-charging technology helps monitor and maintain these conditions within its electric sports cars.
Inside a battery cell, the aging process is influenced by electromechanical actions. Charging causes lithium ions to move from the cathode to the anode, expanding particles, while discharging reverses the process. This movement affects the cell’s electrical resistance, which rises during charging and falls during discharging.
Battery technology explained
Carlos Alberto Cordova Tineo, involved in battery cell development and fast charging at Porsche, explains, “Batteries actually want to be discharged. They have to be forced to charge.” He likens the charging process to a restaurant scenario: having a reservation allows immediate entry, while a spontaneous visit depends on various factors like restaurant capacity and availability.
The restaurant’s capacity and the number of available seats parallel the battery’s state of charge. As the battery ages, its capacity reduces, similar to a restaurant having fewer seats available, leading to longer queues. Tineo states, “This, for lithium-ion batteries, is the deposition of metallic lithium, which is no longer available for energy storage,” a process known as ‘lithium plating.’
Maximising battery life
Porsche strives to simplify ‘restaurant’ access, thus preserving battery longevity through intelligent management and robust chemistry. A control algorithm based on customer habits shows fast charging is selected only 15% of the time. However, Porsche’s stress tests simulate fast charging for half of all cycles, alongside varying temperatures and dynamic driving conditions.
The Taycan benefits from these rigorous tests, featuring improved cells with increased performance and reduced resistance. Enhancements include passive cooling, a new cooling plate with increased capacity, and new busbars for higher currents.
The result is a reduction in fast-charging time from 21.5 minutes to 18 minutes for the current Taycan model, despite increased battery capacity. Charging power has risen to up to 320 kW, and the minimum start temperature for fast charging has decreased to 15 degrees Celsius.
Short charging times, superior performance, maximum safety
Reducing charging breaks aligns with Porsche’s goals for long battery life, minimal CO₂ footprint, and safety. Enhanced driving dynamics are achieved with increased discharge current, facilitating quicker acceleration and improved handling due to weight reduction.
Safety remains a top priority; high-voltage batteries undergo extreme tests, including immersion and corrosion assessments. Crash safety focuses on protecting occupants, with additional internal requirements for hybrid and electric vehicles. “We place all high-voltage components in areas where there is the minimal risk of damage,” says Simon Maurer of the Porsche Cayenne and Macan safety system.
Battery modules face higher stress tests than typical crashes, ensuring no fires occur. The combination of structural optimization and comprehensive safety systems offers the greatest protection, as demonstrated in crash tests at Porsche’s Weissach facility.
Original Story at electriccarsreport.com