N15A-T001 TITLE: Reliable, Safe, Lithium-ion Battery Enabled by a Robust Battery Management System

TECHNOLOGY AREAS: Air Platform, Sensors, Electronics

OBJECTIVE: Develop a Battery Management System (BMS) that is autonomously capable of controlling performance and monitoring battery health. Integrate the BMS to develop a functioning, comprehensive Lithium-ion (Li-ion) battery product.

DESCRIPTION: The Li-ion battery has emerged as the power source of choice in many applications due to its high energy density, long life, low self-discharge and lightweight features. A collection of individual Li-ion cells forms a "module" and a collection of modules forms a "pack". A Li-ion battery product is formed by a collection of modules and packs, which are designed to produce the required electrical power system parameters such as current, voltage, power, capacity and energy. In addition to the cells, the battery consists of wires, connectors, and electronic circuitry which make up the battery management system. The BMS monitors the cell/module/pack performance parameters mentioned above. It is an important component in the overall product; it is the "brains" of the Li-ion battery that monitor and control the operation of the battery under use/abuse conditions to deliver the power output in a safe and reliable manner during the life cycle.

The introduction of Li-ion batteries in the aviation industry has led to roadblocks, such as the fire damage of a Boeing Dreamliner caused by a Li-ion battery, forcing grounding of the fleet. Compared to the other battery chemistries, Li-ion chemistries are much less tolerant of abusive conditions such as over-charge/discharge, high-temperature, or electric shock. The BMS is the key component of the battery that continuously monitors, assesses, and controls the cells, modules, and pack under the following operating conditions: temperature, altitude, humidity, and salt-fog. Lack of maturation of BMS technology is the current roadblock preventing the development of a comprehensive battery product and realizing the full potential of the Li-ion chemistry [1, 5-7].

The features of a robust BMS to be developed should include: advanced/novel sensing techniques, modeling, control and diagnostics and advanced diagnostic systems. The key attributes of a high fidelity system architecture should consist of (i) monitoring (voltage [individual, pack, module, system], current, temperature, exposure to environments [moisture, pressure, salt-fog], cell balancing), (ii) state (charge, health, number of charge/discharge cycles/processes, remaining capacity), (iii) management (data acquisition, standard communication protocol, thermal design, charge control) and (iv) system integration (over-charge/discharge, abnormal conditions, safety and protection, fault detection and alarm, built-in-tests (BITs) for safety compromise alert, diagnostic tests to detect battery nominal and degraded states). The BMS must be a scalable system ranging from around 1 Kilowatt hour (kWh) up to 1 Megawatt hour (MWh) with operational ranges from nominal 28 Volts Direct Current (VDC) up to 400 VDC. Firmware components must comply with MIL-STD-704F [3] and industrial standards. An option for the BMS is to have telemetry that allows real-time wireless monitoring of all battery parameters.

This effort is looking to develop a fully functional Li-ion battery product with a robust BMS that can autonomously and accurately display battery system performance metrics in real time. The fully functional battery must meet the requirements called out in MIL-PRF-29595A [2] and NAVSEA S9310-AQ-SAF-010 [4], which are performance and safety specifications, respectively.

PHASE I: Develop proof of concept for the functionality of a robust, high fidelity battery management system. Determine feasibility for integration into a Li-ion battery product.

PHASE II: Develop a Li-ion battery prototype by integrating robust BMS architectures to demonstrate the functionality in a lab environment.

PHASE III: Finalize BMS for production, to include: hardware (communication ports, charge control, data acquisition, thermal management, sensor monitors, and safety circuits), software (state of health (SOH), state of charge (SOC), and fault detection), and firmware elements (functional status algorithms and built-in-test (BIT) mechanisms to protect the battery). Demonstrate the BMS integrated Li-ion battery product that meets the electrical needs of aircraft in a safe and effective manner in an operational environment, obtain flight certification and transition the technology to appropriate Navy platforms (Ex. F/A-18E/F, H-60, and F-35).

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Li-ion batteries are gaining popularity in commercial aircraft applications. Improvements made under this topic would be directly applicable to the commercial aviation fleet.

REFERENCES:
1. Lu, L., Han, X., Li, J., Hua, J., & Ouyang, M. (2013). A review on the key issues for lithium-ion battery management in electric vehicles. Journal of Power Sources, 226, 272 � 288. doi:10.1016/j.jpowsour.2012.10.060

2. MIL-PRF-29595A - Performance Specification: Batteries and Cells, Lithium, Aircraft, General Specifications for (26 April 2011) http://www.everyspec.com/MIL-PRF/MIL-PRF-010000-29999/MIL-PRF-29595A_32803/

3. MIL-STD-704F, Military Standard: Aircraft Electric Power Characteristics (12 MARCH 2004) http://www.everyspec.com/MIL-STD/MIL-STD-0700-0799/MIL-STD-704F_1083/

4. NAVSEA S9310-AQ-SAF-010 (Second Revision) Technical Manual for Navy Lithium Battery Safety Program Responsibilities and Procedures, 15 July 2010. Retrieved from http://www.public.navy.mil/comnavsafecen/Documents/afloat/Surface/CS/Lithium%20Batteries%20Info/LithBatt_NAVSEA_TMS9310.pdf

5. Spotnitz, R., & Franklin, J. (2003) Abuse behavior of high-power, lithium-ion cells. Journal of Power Sources, 113(1), 81 -100. doi:10.1016/S0378-7753(02)00488-3

6. Stuart, T. A., & Zhu, W. (2011). Modularized battery management for large lithium ion cells. Journal of Power Sources, 196(1), 458 � 464. doi:10.1016/j.jpowsour.2010.04.055

7. Vetter, J., Novák,P., Wagner, M.R., Veit, C., Möller, K.C., Besenhard, J.O.,Winter, M., Wohlfahrt-Mehrens, M., Vogler, C., & Hammouche, A. (2005) Ageing mechanisms in lithium-ion batteries. Journal of Power Sources, 147(1-2), 269 � 281. doi:10.1016/j.jpowsour.2005.01.006

KEYWORDS: Battery Management System; Li-ion battery; Safety System; Battery fault diagnosis; Battery states estimation; Cell performance metrics

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