Method of constructing nickel cadmium batteries prevents excessive gas buildup and allows hermetic sealing of battery for increased service life and reduced maintenance cost

Cohn, E. M.

Frank, H. A.

Juvinall, G. L.

Uchiyama, A. A.

English

NASA Technical Reports Server

August 1975	
.	 B75-10174 
NASA TECH BRIEF 
16	 NASA Pasadena Office
/ 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Nongassing NiCd Battery Cell 
S
Hermetic sealing is essential for NiCd battery cells 
used on spacecraft, as it prevents the loss of electrolyte 
and the resulting loss of performance. Hermetic 
sealing is also desirable in other applications of NiCd 
cells because it extends their life and reduces 
maintenance costs. There is, however, some risk 
associated with hermetic sealing in that it can cause 
excessive gas buildup in the cells, and the resulting 
increase in internal pressure may rupture the casings. 
A new way of constructing NiCd cells prevents this 
pressure increase and allows hermetic sealing to be 
used to extend battery life. 
Two gases can be evolved in NiCd cells: oxygen and 
hydrogen. Oxygen is evolved at the positive plate; its 
rate of formation increases with the increasing state of 
charge of the positive active material. Thus accidental 
overcharging can cause rupture. In the nongassing 
cell, the ratio of positive active material to negative 
active material is approximately 1. . 7, which makes the 
cell negative limited. This means the capacity for 
charge in the cell is limited by the amount of negative 
(cadmium) active material on the negative plates. 
Also, sufficient extra positive active material is 
provided to ensure that the state of charge of the 
positive electrode will remain low enough to minimize 
oxygen formation.
The negative plates contain grid materials which 
exhibit high hydrogen-overvoltage characteristics. As 
the battery is charged to its capacity, these materials 
cause a sudden rise in cell voltage. This sharp rise is 
then used as a signal to stop the charging process, and 
thus stop the formation of hydrogen. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP75-101 74 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Gordon L. Juvinall, Ernst M. Cohn, 
Aiji A. Uchiyama, and
Harvey A. Frank of
Caltech/JPL
(N P0.11853) 
.
Categories: 01 (Electronics - Components 
and Circuitry) 
04 (Materials) 
This document was prepared under the sponsorship of the National
	
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https://ntrs.nasa.gov/search.jsp?R=19750000174 2020-03-19T20:25:21+00:00Z


Nongassing NiCd battery cell

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