N101-018 TITLE: MH-60R Sonar NiCad Battery Reliability Improvement

TECHNOLOGY AREAS: Air Platform, Materials/Processes, Electronics

ACQUISITION PROGRAM: PMA-299, H-60 Helicopter Program, ACAT I

OBJECTIVE: Develop alternate concepts to reduce manufacturing variability, improve reliability and extend the service life of multi-cell Nickel Cadmium (NiCad) rechargeable batteries.

DESCRIPTION: NiCad rechargeable batteries are commonplace in electrical power applications requiring high current drain, flat discharge characteristic, and rapid recharge cycle time. NiCad battery chemistry and associated technology are relatively mature. Cells in the most common standard commercial form factors are a commodity item.

Predicting NiCad cell life expectancy, especially in series-connected multi-cell battery arrays, is a major issue within embedded military applications. These applications are sensitive to product reliability under adverse conditions. Small intra-cell variations in charge storage capacity and internal resistance cause the battery to lose storage capacity with repeated charge cycles, especially in applications where the battery is seldom fully discharged. The problem worsens as the characteristics of individual cells in the battery diverge with repeated high-current charge cycles. Current cost to replace sonar system batteries is upwards of $450,000 each time. Moreover, poor battery reliability has significant intangible impacts to MH-60R fleet readiness as unit repair is a lengthy four to six month process during which the asset is unavailable to support a critical fleet undersea warfare mission. The costs and mission impacts of unreliable and short-lived NiCad cells are therefore of vital importance in this application. An improvement of 10% in the reliability and longevity of NiCad cells would yield large savings in Life Cycle Costs as well as markedly improve system availability. The cost savings and benefits realized in the target transition application alone will offset the SBIR technology investment many times over.

Innovative solutions are sought using either a single method or combination of methods, such as modification screening, improved power management, etc., to yield improved battery reliability and longevity. Possibilities include, but are not limited to, closer cell-to-cell uniformity, integral power management systems, and optimization of cell package construction that increase reliability and service life. Commercial NiCad "AA" cells are the target application for this effort. Techniques developed that could be equally applicable to NiCad batteries of other standard commercial form factors are preferred.

PHASE I: Design and develop concepts and methods for improving battery life expectancy and predictability. Demonstrate feasibility of the concepts developed.

PHASE II: Further develop and refine concepts and methods developed during Phase I. Demonstrate battery reliability, service life and predictability improvements through the development of a prototype system.

PHASE III: Develop a set of specifications, assembly instructions and recommendations demonstrably improving NiCad battery longevity and reliability in high-drain and frequent charge cycle applications such as the MH-60R sonar transducer. Transition to the fleet.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial applications, such as satellites, remote sensing systems, and embedded industrial electronics, which frequently require high-reliability rechargeable power sources capable of high discharge rate and rapid recharge cycles under harsh service conditions and lengthy maintenance intervals.

REFERENCES:
1. "NiCd Technical Handbook," GPI International Ltd, 12 Nov. 2003, 18 Apr. 2009; http://www.gpbatteries.com.hk/html/pdf/NiCd.pdf

2. "NiCad Battery Apps. Manual," Eveready Battery Co, 6 Nov. 2001, 18 April 2009; http://data.energizer.com/PDFs/nickelcadmium_appman.pdf

3. Simpson, Chester. "Battery Charging," National Semiconductor 1995, 18 April 2009; http://www.national.com/appinfo/power/files/f7.pdf

4. "Inaccuracies of Estimating Remaining Cell Capacity with Voltage Measurements Alone," Maxim Application Note 121, Maxim Integrated Products, 23 Apr. 2001, 18 Apr. 2009; http://pdfserv.maxim-ic.com/en/an/AN121.pdf

KEYWORDS: battery; power management; reliability; embedded applications; longevity; manufacturing statistical process control

** TOPIC AUTHOR (TPOC) **

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