Battery Charge Equalizer System

The technology is comprised of a simple and reliable circuit that detects a single bad cell within a battery pack of hundreds of cells and it can monitor and balance the charge of individual cells in series. NASA's BMS is cost effective and can enhance safety and extend the life of critical battery systems, including high-voltage Li-ion batteries that are used in electric vehicles and other next-generation renewable energy applications. The BMS uses saturating transformers in a matrix arrangement to monitor cell voltage and balance the charge of individual battery cells that are in series within a battery string. The system includes a monitoring array and a voltage sensing and balancing system that integrates simply and efficiently with the battery cell array, limiting the number of pins and the complexity of circuitry in the battery. The arrangement has inherent galvanic isolation, low cell leakage currents, and allows a single bad or imbalanced cell in a series of several hundred to be identified. Cell balancing in multi-cell battery strings compensates for weaker cells by equalizing the charge on all the cells in the chain, thus extending battery life. Voltage sensing helps avoid damage from over-voltage that can occur during charging and from under-voltage that can occur through excessive discharging.

In general, individual fuel cells produce relatively small electrical potentials, so fuel cells are "stacked" or placed in series (anode to cathode) to increase the combined voltage and meet the application's requirements. The current is drawn off by connection points, which typically are at the extreme ends of the fuel cell stack. DC power converters reduce or boost the voltage produced at the ends of the stack into a voltage that can be used by attached device. However, these converters add cost, mass, volume, and potential failure points into the fuel cell system. With NASA Glenn's groundbreaking technique, the fuel cell stack includes a plurality of connection points to the device instead of having a fixed number of individual fuel cells. By connecting additional cells in the same stack to the device the system power can be to be tailored to produce the required voltage for the connected device. Initially, this plurality includes a ground, a first connection point, and a second connection point. Additional connection points to the device can be added as needed, resulting in various powers that are available for use. Each connection point allows power to be drawn the combined voltages of the fuel cells located between the connection point and the ground. This configuration permits the voltage to be adjusted to the system power requirements of the device without the need to add DC power converters to the fuel cell system to add additional fuel cell systems to meet the power demand of the device. For larger fuel cell configurations in particular, NASA's innovative technique results in a far less costly, more efficient means of power generation.

The SABERS innovators developed novel lithium-sulfur designs, including sulfur-selenium on graphene cathodes, and lightweight bipolar plate stacking and packaging designs. SABERS is unique in several aspects: it deploys graphene-based manufacturing processes for the cathode and bipolar plates, and it uses a solid-state electrolyte in place of the liquid electrolyte found in other lithium-sulfur battery designs. The team has achieved energy densities over 500 W-hr/kg, and further improvements are expected. SABERS can meet the high-power requirements needed for aircraft take-off. SABERS is lightweight, safe, robust, and reliable. Furthermore, its manufacturing processes are scalable and environmentally friendly. Coin cell and pouch prototypes have been demonstrated to date. Development efforts continue and new portfolio innovations are expected. Major component technologies in SABERS include the following (as listed here and shown in the figure below). S/Se Cathode – Sulfur/Selenium on graphene scaffold (LAR-19556-1, LEW-20228-1) Solid Electrolyte – Solid-state electrolyte composites (LEW-20445-1) Bipolar Stack – Graphene plates (LAR-20257-1) Li-Metal Anode (Proprietary, under development) Packaging (Proprietary, under development) Robust computational models have been developed to support the battery materials design and are available to licensees to evaluate and optimize different materials combinations and performance targets.

Astronauts' lives depend on the safe performance and reliability of lithium-ion (Li-ion) batteries when they are working and living on the International Space Station. These batteries are used to power everything such as communications systems, laptop computers, and breathing devices. Their reliance on safe use of Li-ion batteries led to the research and development of a new device that can more precisely trigger internal short circuits, predict reactions, and establish safeguards through the design of the battery cells and packs. Commercial applications for this device exist as well, as millions of cell phones, laptops, and electronic drive vehicles use Li-ion batteries every day. In helping manufacturers understand why and how Li-ion batteries overheat, this technology improves testing and quality control processes. The uniqueness of this device can be attributed to its simplicity. In a particular embodiment, it is comprised of a small copper and aluminum disc, a copper puck, polyethylene or polypropylene separator, and a layer of wax as thin as the diameter of one human hair. After implantation of the device in a cell, an internal short circuit is induced by exposing the cell to higher temperatures and melting the wax, which is then wicked away by the separator, cathode, and anode, leaving the remaining metal components to come into contact and induce an internal short. Sensors record the cell's reactions. Testing the battery response to the induced internal short provides a 100% reliable testing method to safely test battery containment designs for thermal runaway. This jointly developed and patented technology is available for your company to license and develop into a commercial product. NASA does not manufacture products for commercial sale.

Glenn's novel system supports the NASA Aeronautics Research Mission Directorate (ARMD) strategic plan to leverage advancements in technologies over the next 25 years and beyond, leading to new aircraft configurations with enhanced performance, improved energy efficiency, and reduced CO2 emissions. The electric system is a multi-megawatt micro-grid that converts mechanical energy to electric via generators, and electric energy to mechanical via motor-driven fans. This innovation would use the variation in aircraft throttle settings to produce a high-voltage (20 kilovolts), variable-frequency 9-phase AC distribution system. Using doubly fed electric machines (generator, propulsor, and flywheel) allows for field excitation that can cause variable-frequency or variable speed operation around the commanded throttle setting. The flywheel enables an energy storage system that recovers and reuses energy, while the flywheel slews with the throttle control using the electromagnetic torque produced by the doubly fed electric machine. This design permits both sub-synchronous and super-synchronous operation using limited field excitation power provided through power converters. Finally, the reduced switchgear mass facilitated through the use of a high-frequency AC system, setting-less protection zones, and simplified switches for fault clearance provides enhanced operational capability. This system can be controlled so that fault energy is minimized, preventing collateral damage to aircraft structures even with high voltage distribution. Glenn's innovative system adds performance, efficiency, reliability, and cost savings to cutting-edge hybrid electric technology. This is an early-stage technology requiring additional development, and Glenn welcomes co-development opportunities.