Electric car: Low-voltage battery with sodium instead of lead goes into production

A Chinese battery manufacturer has launched sodium-ion batteries for low-voltage applications in electric vehicles, marking a new milestone in automotive energy storage technology. The company, Xupai, has equipped vehicles from the BAIC brand Arcfox with these batteries, which replace traditional lead-acid batteries used in car electrical systems. This innovation introduces sodium-ion technology into mass production, offering potential improvements over existing solutions in terms of durability, weight, and safety. The transition from lead-acid to sodium-ion batteries represents a shift in the industry's approach to power storage. Lead-acid batteries have been the standard for decades, providing low-voltage power for vehicle electronics, lighting, and other ancillary systems. However, they are associated with frequent failures and maintenance issues, even in modern cars. While lithium-based technologies such as LFP (Lithium Iron Phosphate) have shown promise in addressing some of these shortcomings, they remain costly and rely on critical materials that pose supply chain challenges. Xupai’s sodium-ion batteries are designed specifically for low-voltage applications, serving as auxiliary power sources for onboard systems including infotainment, driver assistance features, and control units. The company offers a range of 12V, 24V, and 48V sodium-ion batteries tailored for different uses, such as starter batteries for internal combustion engines, stop-start systems, mild hybrids, and power supplies for battery-electric vehicles. These batteries aim to provide reliable performance while reducing reliance on scarce resources. Technical specifications highlight the advantages of Xupai’s sodium-ion batteries. For the 12V variant, the company claims a cycle life exceeding 3,000 cycles at 100% depth of discharge. A start-stop version is expected to last up to 180,000 cycles. Weight savings are also notable, with sodium-ion batteries being approximately 55% lighter than their lead-acid counterparts. Each model includes a Battery Management System (BMS) compatible with CAN or CAN-FD communication protocols, ensuring functional safety levels meeting ASIL B standards. Comparisons with conventional lead-acid AGM or EFB batteries reveal significant differences in performance. Traditional lead-acid batteries typically offer 200 to 400 cycles at high discharge depths and energy densities of around 30 to 40 Wh/kg. In contrast, sodium-ion low-voltage batteries achieve energy densities of approximately 80 to 110 Wh/kg, nearly three times higher. A prototype developed by German engineering firm IAV and Chinese cell manufacturer HiNa demonstrated impressive capabilities, featuring a 12V system with 70 Ah capacity and 840 Wh energy density in just 10 kg, operating within a temperature range of -40°C to +60°C during discharge. Safety considerations are another key advantage of sodium-ion technology. Unlike lithium-based chemistries such as NMC or NCA, sodium-ion cells exhibit lower susceptibility to thermal runaway. Manufacturers like Altris describe the technology as having “zero thermal runaway.” Compared to lead-acid batteries, sodium-ion alternatives eliminate risks related to sulfuric acid, corrosion, and gas generation under overcharge conditions. Cells undergo testing against the Chinese standard GB/T-31485 for overcharge resistance, and integrated BMS systems monitor voltage and temperature, allowing controlled shutdown in case of short circuits. Xupai positions its batteries as plug-and-play replacements in standard sizes, requiring minimal modifications to vehicle electrical systems. BAIC’s involvement extends beyond low-voltage applications. The company’s research department has developed a prismatic sodium-ion cell with an energy density exceeding 170 Wh/kg, capable of rapid charging at a rate of 4C in about 11 minutes. This development points toward broader integration of sodium-ion technology in traction battery systems, further expanding its role in the electric vehicle landscape.