moisture and oxygen gas do not exist. However, work is ongoing in this area to understand and improve the plating process. For example, JPL is investigating the use of a lithium alloy to replace the pure lithium. The proper alloy together with a stable high conductivity electrolyte is desirable. Controlling the operating temperature of any cell is an issue that must be considered by the user. However, it is more of a concern for the ambient temperature lithium cell user. The melting point of lithium is 179°C. If a cell and its related battery case do not have adequate heat removal capability and/or the discharge rate is high, it is possible for the temperature to exceed safe operating limits. These heat removal issues and proper handling and storage are user safety concerns. The NASA Role for Rechargeable Lithium Cells As described above, the ambient temperature rechargeable lithium cells will be smaller than 50 Ah size and in a prismatic configuration. Fig. 8 indicates the projected role these cells will play in the framework of existing electrochemical power sources. The spacecraft systems have been divided into low power, <1 kW, which require 50 Ah size or smaller cells and high power, > 1 kW, which require cells greater than 50 Ah. The Ni-Cd battery is the system of choice for the low power spacecraft and will continue to be for a number of years. For the high power spacecraft, e.g. Hubble Space
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