A local company has started using Swiss-made sodium- nickel chloride batteries – the development of which started in South Africa in the mid-1970s – to power part of its electric-vehicle fleet.

Peter Langley, a senior technologist at Eskom Enterprises’ Technology Services International (TSI) division, explains that, by acquiring the three batteries from Switzerland’s MES-DEA, the company wants to confirm the technical feasibility of using them in a variety of applications. One of the batteries will be used on a sedan, while the other two will power a game-viewing truck, says Langley, adding that a detailed report on the performance of the truck should be available by the end of the year.

Production of the batteries started in October last year, and the three acquired by TSI were the first to be imported into Africa and are among the 200 which had been made by the end of December. Eskom Enterprises is the unregu-lated arm of Eskom Holdings, the national power utility.

The Swiss firm hopes to make 1 000 batteries this year, increasing its output to 10 000 units a year in the near future. Early work on the project to produce the sodium-nickel chloride battery – known as the Zebra battery – dates back nearly 30 years, when a group of scientists working for the CSIR and Anglo American started investigations on partially-chlorinated transition-metal carbides and related interstitial hard-metal com- pounds as positive ele- ments in high-energy- density high-temperature secondary batteries.

This development took place at a time when the other two leading high-temperature systems – sodium sulphur and lithium iron sulphide – were enjoying world-wide attention. Both these systems have since proved to be unsuitable.

The Zebra cell has a central positive electrode consisting of nickel and sodium chloride, together with a liquid electrolyte tetrachloroaluminate contained within a beta alumina tube electrolyte. The cell operates in a temperature range of 270