Underwater batteries keep exploration on the Move

A custom-made lithium-ion battery system will power Move, an unmanned, autonomous deep sea exploration vehicle on missions lasting up to nine months.

A Saft lithium-ion battery system will power Move, an unmanned, autonomous deep sea exploration vehicle on missions lasting up to nine months, while it crawls the seabed at depths of several thousand metres to make continuous observations of processes at the ocean floor.

Move, which resembles the well-known Mars rovers, is one of the new generation of deep sea exploration vehicles under development at Marum, the University of Bremen's centre of marine environmental research and NIOZ, the Netherlands Institute for Sea Research.

It is designed to serve as a mobile platform for various scientific instruments and experiments and has a maximum speed of 5cm/s and a range of 1km.

An acoustic link to the surface is used to interrogate the vehicle and retrieve status information, scientific data and video and still images from the onboard camera.

Dr Christoph Waldmann, Marum's Project Manager for Move, said: "We face many of the same technological challenges encountered in space exploration".

"There are similar constraints regarding energy supply, communication bandwidth and controllability of the deployed systems".

"We decided to use a Saft lithium-ion battery system in the Move vehicle because it offered the ideal combination of high energy content, long-life, reliability and low self-discharge".

"This will enable us to deploy the vehicle on missions of up to nine months, to make repeated long term observations on the ocean floor without needing to recover the vehicle to recharge or change the battery pack".

Saft has developed a special, modular integrated battery system for Move, based on VLE lithium-ion cells.

These cells were originally developed for hybrid and electric vehicle applications to pack as much power as possible into a lightweight and space efficient package.

The Move battery modules comprise three parallel strings of seven VLE 45Ah cells, providing a nominal 24V and 135Ah capacity, mounted in a tube to withstand deep-water pressures, and complete with an electronic control management system for the monitoring of charge and discharge voltages and cell temperatures.

Four modules have been manufactured, and these can be mounted on the vehicle and connected in parallel to provide the appropriate battery duration for each seabed mission, up to a total capacity of 540Ah and 13.2kWh.

Move has successfully completed sea trials in the Skagerrak, the deep water strait between Norway and the southwest coast of Sweden, at depths down to 650m.

It is now moving on to carry out its first scientific missions in shallow water regions of the North and Baltic Sea.

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