SAE J2997_202606

This document provides recommendations involving BEV battery data retention and battery design that enhance the potential for BEV battery reuse and serviceability and that can improve recyclability. These recommendations have been developed by a group of professionals skilled in the secondary-use of batteries and in the research, development, and manufacture of BEV batteries and battery systems. Many, if not most, Battery Electric Vehicle (BEV) battery packs removed from original service have a capacity that could be useful in a second life application. Some battery packs can be placed directly into secondary-use, while some packs are in a condition that refurbishment can restore them for secondary-use. A secondary-use could be for installation in a BEV as a replacement pack, integration into a stationary energy storage system, or breaking down and reconstituting into smaller or larger battery packs. Designing for secondary-use can be financially beneficial versus immediate recycling. Battery pack data availability can enhance EV residual values because certainty improves valuations as less “cushion” needs to be added to compensate for underperforming packs. Improved battery pack design can reduce the time and cost of battery repair and/or refurbishing. Further, the secondary-use of EV batteries improves a battery’s carbon footprint as there is a negligible amount of carbon expended in secondary-use as compared to their initial manufacture. A battery pack removed from original service often has a capacity that would be useful in stationary storage because volume and energy density are not as critical as it is in an automobile. Because a battery pack is only as strong as its weakest link, replacing an underperforming module (or modules) can enable a pack to be reinstalled in its original use or utilized in a secondary-use with minimum effort if the design of the battery pack supports secondary-use and repair. The physical design of a battery pack can have a major impact on its ability to be repaired or integrated into secondary-use. A battery pack that has mechanical fasteners that can be easily separated is preferable to one that is tab welded. At present, there is no practical way to separate tab-welded cells or modules for secondary-use. Similarly, there is no practical or cost-efficient method to remove adhesive and/or encapsulating material that binds cells and modules together as seen in some designs. Design for secondary-use is an important consideration to reduce a battery pack’s life-cycle cost and carbon footprint. Regardless of the design of a pack, any battery considered for secondary-use should be evaluated for safety as well as its state of health (SOH) and capacity. Two of the key indicators for SOH are the individual cell resistances and capacities. While many manufacturers and system integrators have their own method of analyzing battery data to reach an estimate of the SOH and capacity, the basic data used are the same. Data used in SOH estimations are values or changes in the values of voltage, current, temperature, and impedance. Unless the data is stored in the cloud and/or the battery management system (BMS) and made available for download and analysis, this evaluation can be man-hour time consuming. This evaluation also requires costly machine time. The challenge is that the cost of man-hours and machine time continue to increase. As the cost of new batteries continues to decrease, and the more man-hours and/or machine time required in analyzing batteries for secondary-use, the less attractive a battery pack will be for secondary-use. It would be beneficial for the industry to establish a range of best practices that would improve the economics of EV residual values and increase secondary-use while also decreasing the total lifetime carbon footprint of batteries.