One of the greatest challenges in front of transport infrastructure engineers, who aim to design electric locomotives, is to find a cost effective and efficient way to extend battery life. The example that illustrates this is the first all-electric, battery-powered locomotive in the U.S. called Norfolk Southern Railway No. 999. It runs on one thousand lead-acid batteries, all of which should be fully charged in order to keep the locomotive in motion.
A team from Penn State led by Christopher Rahn, professor of mechanical engineering, has discovered a way to solve the problem by developing experimental batteries that are rechargeable, cheap and simple.
Considering that sulfation is the main cause for damage of lead-acid batteries, the team decided to look into ways to reverse the process and by using limited number of sensors, electronics and supporting software, to rejuvenate the battery.
Together with research assistants Ying Shi and Christopher Ferone, Rahn exposed a lead-acid battery to conditions found in electric locomotives, and identified the main aging mechanisms of the power sources. Using electroimpedance spectroscopy, the team managed to identify sulfation and establish a charging algorithm.
The results of the study were published in the Journal of Power Sources. The scientists reported that this algorithm could control battery charging, reduce sulfation and stop charging before other forms of degradation take place.
In their study, the team compares the new battery with an old one, and reported that they were able to not only increase cell capacity by 41 percent and the overall battery capacity by 30 percent, but also they were able to desulfate it.
In addition, the researchers identified other processes that are responsible for capacity reduction. These include positive electrode corrosion, irreversible hard sulfation, positive electrode softening, electrolyte stratification and internal short-circulating and mechanical damage.
The aim of the team now is to find a model that can replace electroimpedance spectroscopy and allow them to charge a battery to the point just before sulfation. They hope that by developing this, they will be able to completely prevent the process from happening.
The NS999 is being fitted with Lead-Carbon batteries from Axion Power. It should be back in service starting in the 1st quarter of 2013.