1、Lessons Learned Entry: 0568Lesson Info:a71 Lesson Number: 0568a71 Lesson Date: 1997-08-28a71 Submitting Organization: JPLa71 Submitted by: K. Clark/D. OberhettingerSubject: Battery “Popping“ During ATLO (Assembly Test and Launch Operations) Due to Horizontal Mounting Abstract: During Mars Global Sur
2、veyor system test, it was discovered that horizontally mounted nickel-hydrogen battery cells are subject to electrolyte “pooling” in a 1 g. environment. This can damage the cells; high charge rates (and temperatures) increase the likelihood of damage. Some measures to prevent battery popping (rapid
3、oxygen-hydrogen recombination under fast charge conditions) are recommended for nickel-hydrogen batteries during any ground phase.Description of Driving Event: Mars Global Surveyor (MGS) carries two nickel-hydrogen (NiH2) battery assemblies: one mounted to the +Y and one to the -Y propulsion module.
4、 Each assembly consists of eight 20Ahr NiH2 common pressure vessels (CPVs) in a honeycomb composite enclosure mounted on an aluminum baseplate. During MGS system test, shortly after installation of the batteries on the spacecraft, an intermittent “popping“ or “snapping“ sound issued from both batter
5、ies. This noise was most likely caused by oxygen-hydrogen (H2/O2) recombination in the battery under the fast charge rate conditions normally present throughout the charge cycle. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-H2/O2 recombination is
6、a natural chemical process which occurs mostly during the late charge and early discharge stages of NiH2 battery operation. Audible popping occurs during H2/O2 recombination when a large enough oxygen bubble is allowed to form on an electrode plate inside the cell stack before it can recombine with
7、hydrogen. When this bubble finally does recombine, a popping sound results. Such popping may induce significant damage to cell plates and may reduce battery cycle life.This phenomenon was exacerbated by the MGS practice of mounting and testing the battery on its side (i.e., horizontally) in a 1 g. e
8、nvironment. Instead of remaining fully contained within the porous electrodes, a small amount of the liquid electrolyte was drawn by the force of gravity to the bottom of the horizontal CPV. The liquid pressure from this “pooling“ of electrolyte promoted the formation of oxygen bubbles large enough
9、to recombine violently. Such pooling cannot occur in a zero g. environment.Use of the flight batteries was judged to represent a low risk to MGS mission success. X-ray inspection showed that the popping had caused some deformation of the cell plates. However, charge retention testing showed no degra
10、dation in battery performance, and the item features a heritage design and robust capacity.refer to D description D Figure 1. NiH2 CPV Positioned Vertically (only the upper of two stack sets is shown) Additional Keyword(s): Battery ChargingReference(s):Provided by IHSNot for ResaleNo reproduction or
11、 networking permitted without license from IHS-,-,-a71 Problem/Failure Report No. B0M9XUa71 Walker, S., “Battery Noise Anomaly Close-Out Engineering Analysis,“ September 26, 1996Lesson(s) Learned: A nickel-hydrogen battery design where the cells are mounted on their sides (i.e., horizontally), inste
12、ad of in the vertical position shown in Figure 1, increases the potential for electrolyte “pooling“ in a 1 g. environment and for possible damage to cells. High charge rates (and temperatures) increase the likelihood of battery popping.Recommendation(s): For nickel-hydrogen batteries, take precautio
13、ns against battery popping during any ground phase:1. Reduce the charge rate as the batteries approach full charge.2. To minimize the likelihood of pooling, ensure that battery cells contain no excess electrolyte.3. Mount batteries to minimize electrolyte pooling in a 1 g. environment.Evidence of Re
14、currence Control Effectiveness: N/ADocuments Related to Lesson: N/AMission Directorate(s): N/AAdditional Key Phrase(s): a71 Energya71 HardwareAdditional Info: Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-Approval Info: a71 Approval Date: 1997-10-10a71 Approval Name: Carol Dumaina71 Approval Organization: 125-204a71 Approval Phone Number: 818-354-8242Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
