Description
Priority 2 activities will only be initiated on the explicit request of at least one delegation.
The objective of the activity is to demonstrate that Li-ion batteries based on high energy density European cells can be operated without bypass during any telecom mission and can be passivated at end-of-life according to Clean Space requirements.
Targeted Improvements: The benefit will be to save between 5 and 10 kg and the related procurement and production cost (50 to 100 kEuro) on each battery design.
Current Li ion batteries (e.g. SAFT VES 140/180) are delivered with a bypass. Bypass devices are introduced in the design of the Li ion battery in order to cope with the failure modes of the cells. This bypass solution was directly re-used from NiH2 battery designs, due to the lack of heritage and knowledge of the Li-ion technology at that time. However SAFT VES Li ion cells have been flying for years, so now their behaviour and reliability are better understood, and so far there is no known tendency that bypass activation will be necessary within the foreseeable future.
In 2002, an ARTES 3 study (Contract 16832/02/NL/US) was conducted on the VES140 Li-ion cells in order to demonstrate the feasibility of the by-pass removal at battery level. A similar GSTP3 (18398/04/NL/JD) study was conducted for the VES180 (G5) Li-ion cells.
The main conclusion was that a cell failure will ultimately result in the failed cell package over-discharge and inversion of the cell, resulting into a shorted cell-package as a pure resistor. An electrochemical and electrical model of the Li-ion cell has been developed to predict the behaviour of the battery in case of failure.
Using the outcome of these studies, a first in flight experimentation on VES140 batteries has been conducted with success on RASCOM satellite at the end of its mission. Nevertheless, the RASCOM mission remains a unique case so far and additional work is necessary to complete the demonstration for any telecom mission on any orbit.
Battery Passivation is required at end of mission. Methods for power subsytem passivation are currently under studies: in the activity GSP “Environmental Impact on Power Systems After End-of-Life” and a GSTP activity is about to start "Spacecraft Power System Passivation at End of Mission”. The by-pass removal leads to a new cell management, requiring reversal of cell, and this cell reversal can also be a method for passivating the battery at end-of-mission.
Work logic
A first review of the cell reliability and FMECA on past missions will be conducted.
Then a study of cell self-short in worst case conditions (analysis and tests of cell and module reversal, battery management in case of failure,) will be performed. The last step will be to demonstrate EOL passivation of the battery (aged cell reversal, module reversal at end of mission).
Procurement Policy: C(2) = A relevant participation (in terms of quality and quantity) of non-primes (incl. SMEs) is required. For additional information please go to EMITS news "Industrial Policy measures for non-primes, SMEs and R&D entities in ESA programmes".