REG NASA-LLIS-5336-2011 Lessons Learned Nickel-Hydrogen (NiH2) Common Pressure Vessel (CPV) Cell Capacity Loss and Voltage Collapse.pdf

1、Public Lessons Learned Entry: 5336 Lesson Info: Lesson Number: 5336 Submitting Organization: HQ Submitted by: Ryan Luttrell Subject: Nickel-Hydrogen (NiH2) Common Pressure Vessel (CPV) Cell Capacity Loss and Voltage Collapse Abstract: A NASA Engineering and Safety Center (NESC) team discovered that

2、the design of NiH2 CPV batteries may be susceptible to a unique electrolyte bridging between the two internal cells resulting in undesired ionic current flow. This condition can lead to depletion of the capacity within one of the two cells. Description of Driving Event: The Wilkinson Microwave Aniso

3、tropy Probe (WMAP) was launched in 2001 and outfitted with an 11 cell CPV NiH2 battery. WMAP was designed to operate in full sun conditions. An unexpected series of discrete voltage drops began in August 2009 that were clearly traceable to the loss of one of the two individual cells contained within

4、 multiple battery CPVs. An examination of the limited telemetry available provided confirmation that each event was associated with a transient thermal load increase that occurred in conjunction with each step loss of voltage. Lesson(s) Learned: NiH2 CPV battery cell designs are susceptible to a uni

5、que electrolyte bridging between the two internal cells that can potentially result in undesired ionic current flow, which can ultimately deplete the capacity within one of the two cells. The internal design configuration of a normal CPV allows free material transport between cells as both cells wit

6、hin a CPV are intended to share the hydrogen gas necessary for NiH2 cell functionality. Two conditions were identified where it is possible for free potassium hydroxide (KOH) electrolyte to creep between the cell stacks and to establish an undesirable conductive ionic pathway that effectively shorts

7、 out one of the two cells within the CPV. Those conditions are: 1) activating the NiH2 CPV cells with excess electrolyte present or 2) allowing the cells to reach very low states of charge during operation. Based on observations and available data, once the electrolyte bridge is established there ar

8、e no effective means to eliminate the problem with the possible exception of fully reconditioning the battery cell, or at least extended operation (up to a few weeks) in an open circuit condition. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Figur

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11、 Operations P16840 Pressure Vesshnical Bulletin entified PossibC/10 and C/4) n of the WMAPC) needed to roblem Resolutel (CPV) NickelNo. 11-01 le Electrolyte Bwas observed tbattery and in be in place to reion Team (PRTHydrogen Cellridging Locationo be effective ina similar laboraduce the possi), NESC

12、 Docum, Aerospace Res at tory bility ent port Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Mission Directorate(s): Exploration Systems Additional Key Phrase(s): Power Spacecraft and Spacecraft Instruments Additional Info: Project: N/A Approval Info: Approval Date: 2011-02-04 Approval Name: mbell Approval Organization: HQ Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-