The 'Extreme Everest' expedition has recently completed its groundbreaking expedition to the summit of Everest to research the effects of low oxygen on the body. Fundamental to the expedition was the ability to power the research apparatus and associated equipment. Exide Technologies provided the batteries used in the 4 laboratories – the highest of which was at 7,900m asl (above sea level). The batteries are the same "Dryfit" Gel batteries that are used in leisure and sports activities, such as boats, caravans, wheelchairs and golf caddies. During the expedition they were able to be used where people were eating or sleeping because of their extremely low emissions and the fact that no acid vapours are released, unlike conventional lead acid batteries. Another safety advantage is that the electrolyte is trapped in gel, so even when one of the battery casings was damaged because of an accidental impact, it was still serviceable.
The team of scientists and researchers made the first ever measurement of the level of oxygen in human blood at 8400m, on the balcony of Everest. This was the centrepiece of an extensive and continuing programme of research into hypoxia (low oxygen levels) and human performance at extreme altitude aimed at improving the care of the critically ill and other patients where hypoxia is a fundamental problem. The findings now being analysed will be used to improve intensive care treatment for patients suffering from a range of life-threatening conditions including blue babies, congenital heart disease, chronic bronchitis, cystic fibrosis etc.
Not only were the batteries used in extreme conditions, down to –10oC, but they were pushed to their limits and discharged to depths greater than ordinarily recommended. This was because the batteries were used in conjunction with a generator and the team wanted to minimise the generator usage and to ensure a smooth and continual supply of power to the sensitive medical equipment; if there was any disruption to the blood gas analyser for example, the whole experiment would have to be restarted.
Paul Richards was responsible for the power systems and comments, "The Exide batteries exceeded our expectations. Although we really punished them, the capacity levels were maintained, with only a slight loss in capacity on the base camp lab batteries because they were the most heavily used. When we had to temporarily abandon the highest laboratory because of severe weather, we left behind the batteries, with just a solar charging system to keep them 'ticking over'. We were pleasantly surprised to find that they still functioned. It's fair to say that the scientists started to take the batteries for granted and although the batteries' status was monitored, the low power alarm systems weren't even triggered."
After the expedition returned to the UK, Mike Carrington, Senior Applications Engineer at Exide Technologies carried out tests on thebatteries, "Initial tests showed that the batteries had been left fully discharged after the expedition, for a long period, which is not recommended. However, we found that they retained 80% of their capacity upon first charge and they increased capacity with further charge /discharge cycles, which is impressive. Expeditions like this allow us to say with confidence that our Sonnenschein 'Dryfit' batteries can be used up to 10,000m elevation and in temperatures down to – 40oC, although thankfully most of our customers won't be operating in such extremes."