Texas A&M Researchers Studying Car Batteries

From DieHards to Delcos, most car batteries are pretty much created equal: they eventually lose their juice.

Two Texas A&M University physicists are looking into ways to keep batteries going and going and going, and finding answers that embrace both biology and chemistry. Their project also hints at something that has puzzled biologists for more than 100 years: creation of electrical fields around plant roots while they grow.

Wayne Saslow and Joseph Ross have found that even when a battery is idle, it is still electrically active because the voltage profile moving across the battery acid of an idle battery is not a flat line. This voltage profile could be the key to making future batteries last longer.

For their work, Saslow and Ross studied a 12-volt motorcycle battery. It was selected because it is “dry charged,” meaning it is stored with no battery acid that could spill out when cut open to study it. Battery acid is 35 percent sulfuric acid and normally is added at the store at purchase time. Saslow and Ross and graduate student Robert Haaser added sulfuric acid in the laboratory.

A car battery usually gets its 12 volts by using six 2-volt cells in a series, the researchers say. The battery gets additional current capacity by making each 2-volt cell as big as possible. For a motorcycle battery, each individual cell is really 8 sub-cells in parallel.

Saslow and Ross used one sub-cell, which contains a positive (red) lead oxide electrode and a negative (black) lead electrode, separated by one millimeter of fiberglass immersed in sulfuric acid. They increased the separation to about a centimeter, inserted five 3-inch long platinum probes and measured the voltage of each probe.

When they plotted the voltage, they found that a battery at rest – neither charging or discharging – showed a quadratic (sloped) curve, not a flat line.

“The quadratic curve means there are chemical reactions and ion flow, but no net electric current flow,” Saslow confirms. “The faster such reactions go, the more voltage results. We’re trying to use our measurements to learn more about what goes on inside batteries.”

Saslow said there are two types of chemical reactions at a battery’s electrodes. One is Faradiac, which leads to electrical currents, and the other is non-Faradiac, which are ordinary chemical reactions and no current flow. If a battery sits for six months with no activity, it goes bad, he said, because of chemical reactions that demand ions from the electrodes and the battery acid.

“If we can monitor batteries better, it might help us learn how to make them last longer,” he added.

Car batteries, he said, have not changed much in the last 50 years. A battery that claims it has 600 CCAs (cold cranking amps) uses that much only when it activates the starting motor. It only uses about 6 amps for headlights, Saslow said.

“Batteries have 48 sub-cells,” Saslow said, “and if only one cell is faulty, that can kill the entire battery. We need to find a way to locate the weakest sub-cells and then recharge them before they go bad.

“The next step for us is to monitor more batteries and collect more data and match it with previous findings,” he said. “But there is no doubt that there is a lot more going on inside a battery than we had thought.”

Saslow and Ross said their research could result in better design of car batteries and new diagnostic tests to measure a battery’s power and longevity.

And the biological implications?

“I have on my bookshelf a very old book titled Bio-Electrics and Growth,” he continues. “It describes an effect biologists have known about for over a hundred years and no one can explain. When plant roots grow, there are local electric fields with no current flow. The faster the roots grow, the bigger the local electric fields.

“That’s just like what we are seeing when the battery is just sitting there,” he adds. “You have to think of biological growth as a fancy chemical reaction that demands ions but no electric current. That’s exactly what we see in the battery when there is no electric current flow. We had no idea this work would relate to biology, but it certainly does.”

Contact: Keith Randall at (409) 845-4644 or Wayne Saslow at (409) 845-4841.

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