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Product category: Batteries and Chargers
News Release from: Saft Rechargeable Battery Systems | Subject: VES140S Li-ion cells
Edited by the Electronicstalk Editorial Team on 17 October 2005

Batteries keep satellite
running through eclipses

Saft's lithium-ion (Li-ion) battery technology achieved two important firsts with last week's successful launch of France's new Syracuse IIIA secure military telecommunications satellite

Not only is this the first time that Saft has supplied its rechargeable Li-ion batteries, developed to provide a reliable power source in a compact, weight-saving package, to Alcatel Alenia Space, the prime contractor for Syracuse III. It is also the first-ever application of Li-ion batteries in a military GEO (geosynchronous) satellite.

Syracuse IIIA is the first of two GEO military communication satellites that will be operated by the DGA within France's ministry of defence (Syracuse IIIB is scheduled for launch in 2006), to form the cornerstone of a European military satcom system shared by NATO allies.

Normally, the onboard electronic systems on the Syracuse III satellites will rely on solar panels for their electric power.

However, the nature of the GEO orbit means that during the twice-yearly equinoxes, around 21st March and 21st September, the panels will be 'eclipsed' by the Earth, with no direct sunlight.

During these periods of around 22 days on each side of the equinox, the onboard batteries have to fulfil the demanding role of providing sufficient power to ensure the satellite's continued, uninterrupted operation, over a projected 15-year service life.

For both Syracuse IIIA and B, Saft has developed a battery system comprising two packs connected in series.

The packs are made up of 12 modules connected in series, each module comprising three VES140S cells in parallel.

The VES cells are manufactured in Saft's industrial factory in Bordeaux, France and integrated into the packs and tested at Saft's facility In Poitiers, France.

The Syracuse III project confirms the growing trend within the satellite industry towards using the latest Li-ion battery technology instead of nickel-cadmium (Ni-Cd) or nickel-hydrogen (Ni-H2).

Saft's VES140S Li-ion cells are qualified by both ESA and CNES (Centre National d'Etudes Spatiales) for all satellite applications.

Although this is their first military GEO application, they had already entered service on two commercial GEO satellites, and a further six Li-ion batteries have been delivered by Saft for GEO projects launching in 2006.

One of the main advantages of Li-ion battery technology is its capability to store the same amount of energy as an Ni-H2 battery in a smaller package, offering a weight saving of around 50%.

This enables the satellite operator and manufacturer to utilise more of the satellite's crucial overall mass to carry a larger operational payload.

In the case of the Syracuse III the weight saved by the Li-ion batteries has enabled additional anti-countermeasure protection to be installed.

A further benefit of Li-ion technology is its low self-discharge characteristics, which enable the Syracuse III batteries to retain around 98% of their charge even after a month of storage.

So, they do not need recharging while the satellite is on the launch pad, unlike Ni-H2 batteries that require charging until the last few hours before launch.

In other words, pre-launch management is simplified, as, once the satellite is installed in the launch vehicle, safety and thermal issues associated with battery charging are suppressed.

By using the weight-saving capability of the Li-ion batteries to increase the operational payload, the operator places a consequently greater demand on the satellite power system.

This would normally require a significant increase in the area of the solar panels.

However, the superior charging efficiency of Li-ion enables them to make very efficient use of the charge current supplied by the solar panels.

So the increase in panel size is minimised.

The Syracuse IIIA satellite was launched from Europe's Spaceport in French Guiana.

It had a total weight at launch of 3725kg and was carried into space by an Ariane 5GS launch vehicle that also uses a variety of Saft specialised spacecraft Ag-Zn and Ni-Cd batteries to support its in-flight systems. Request a free brochure from Saft Rechargeable Battery Systems....

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