January 5, 2013
Engineers Working On Ways To Prolong Electric Locomotive’s Battery Life
redOrbit Staff & Wire Reports - Your Universe Online
A new charging algorithm developed by researchers at one US university could help extend battery life in the country's first all-electric, battery-powered locomotive, according to reports.The locomotive in question, Norfolk Southern Railway No. 999, uses batteries similar to those used in automobiles. Its batteries are rechargeable for a time, but ultimately die out, often due to degradation of the power source caused by lead sulfate accumulation resulting from frequent charging and discharging -- a condition known as sulfation.
When just one of the 1,000 lead-acid batteries that power the locomotive fails because of sulfation, it halts the locomotive completely. In an attempt to overcome this obstacle, a team of Penn State University researchers, including Mechanical Engineering Professor Christopher Rahn, set out to find cost-effective ways to prolong the life of No. 999's power source.
"The methods had to be nondestructive, simple and cheap -- using as few sensors, electronics and supporting hardware as possible while still remaining effective at identifying and decreasing sulfation," the university said in a recent statement.
Rahn added he and mechanical engineering research assistants Ying Shi and Christopher Ferone "wanted to reverse the sulfation to rejuvenate the battery and bring it back to life."
To do so, the three researchers cycled one of the batteries, simulating the normal wear and tear it would experience powering the locomotive, over a three-month period and then using a process known as electroimpedance spectroscopy and full charge/discharge to detect the primary aging mechanisms.
"Through this, the researchers identified sulfation in one of the six battery cells," the university said. "They then designed a charging algorithm that could charge the battery and reduce sulfation, but was also able to stop charging before other forms of degradation occurred. The algorithm successfully revived the dead cell and increased the overall capacity."
They then compared the tested battery to a new one, and while Rahn said they were not able to increase its capacity to like-new levels, they were able to "get a big boost" out of the revitalized power cell. In fact, according to results published in the latest edition of the Journal of Power Sources, they increased the cell capacity by 41-percent and the overall battery capacity by 30-percent.
The university said the results could have been better had sulfation been the lone aging mechanism impacting the batteries' performance. However, that was not the case, as Rahn said there may have been a water-loss issue with some of the other cells -- a problem that cannot be corrected in this type of battery.
"Other mechanisms that can damage lead-acid batteries include positive electrode corrosion, irreversible hard sulfation, positive electrode softening or shedding, electrolyte stratification, internal short-circuiting and mechanical damage," the university said. "The researchers are now developing alternative models to replace the electroimpedance spectroscopy model that would allow charging right up to, but not past, sulfation in batteries where sulfation is not yet present, hoping to prevent it from occurring in the first place."