The objectives which have directed the modelling of the lithium cell for space applications (but the approach may be extended to other needs) were to achieve an equivalent electrical network of the cell capable to predict its electrical performances combined with its thermal features. The derivation of the Zimmerman approach to model a storage cell has resulted to give a very flexible representation as the beginning of life of the cell is perfectly described with 43 constants. This number may appear to be high. However each constant is closely related to physical, electrochemical features of the cell and the active material which enter in its manufacturing. As a consequence simplified relationships between these constants and the cell data sheet are possible. They have not been detailed in this paper for length constraints reasons. Furthermore these constants may be utilised to generate additional relationships in order to predict the ageing effect of the cell operating in a long term mission with variable stress conditions. This model extension has been already experimented for NiCd (2) and will be the scope of the next step of investigation
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