The modern day lead acid battery would be very different — both more expensive and less efficient — were it not for the contribution of David Prengaman one of the world’s top specialists in the metallurgy of lead alloys and related energy storage. Historian Kevin Desmond reports.

The Lead Pope

R David Prengaman of Dallas, Texas is one of the top specialists in the fields of metallurgy of lead alloys and lead-acid batteries, in particular the innovation of lead anodes for electrowinning metals, and recycling processes for lead acid batteries to produce high quality lead and lead alloys. The German company, Metallgesellschaft, once aptly nicknamed him “The Lead Pope.”

R. David Prengaman (the R stands for Raymond) was born in 1943 in Pittsburgh, Pennsylvania. While his father was employed as a machinist for Westinghouse, his grandfather and five of his father’s brothers also worked there as machinists.

“None of my father’s brothers or sisters graduated from college. My father was always interested in maths and science and taught himself calculus,” he recalled. “I was the oldest of six children and have worked all my life to earn enough money. I had a newspaper round, picked berries in the summer to sell in the grocery stores, and worked as a caddy at the local country club. I attended Catholic school where the nuns gave me a wonderful education.

“My father would take several children to the Carnegie Museum whenever the weather was rainy or cold. After many visits I knew that I wanted to do something in science perhaps in Medicine or engineering.”

Direction

When he was 14 years old, Prengaman was selected to attend the Joe Berg Science seminars. These involved visits to many company facilities and laboratories in the Pittsburgh area to see scientists or engineers at work. The first factory that they visited was Pittsburgh Steel Company’s metallurgical laboratory. At that time the various phases in steel were being correlated with the properties of the steel. When it was his turn to look into the microscope at the various steel samples, “It was as though I had looked at them all my life. I knew then that I wanted to be a metallurgical engineer,” he said.

He attended the Carnegie Institute of Technology. Its closeness to the family home enabled him to commute to the institute each day as his father did not have enough money to enable him to live on campus. The research which gained him his BS degree in 1965, was aimed at segregation in alloys and the structures generated during the solidification.

Original continuous cast PB-CA-SN billet prior to rolling.

Having loved golf since his childhood, David now played for the Carnegie Institute’s golf team. “As university golf team members, we were permitted to miss some classes due to practice or travel for matches with other universities. Most of these matches were on Thursday afternoons when I had a metallography laboratory. The professor was angry that I kept missing his classes, but gave me the opportunity to make up the classes at night,” he said.

To frustrate me he gave me the most difficult samples to polish and etch including copper and steel with lead in the structure as well as lead and lead tin solder samples. There could be no scratches on the samples or lead pulled out of the samples.

This proved the best training, as the young graduate developed polishing and etching techniques that he would take with him through his career in lead that were extremely difficult for others to duplicate.

In 1967, Prengaman obtained his Masters in metallurgy and materials science. His research was into the development of rolling textures in high chromium, high nickel stainless steels and the properties and corrosion resistance of these materials. The work was aimed at the Ford Motor Company as the firm was interested in stainless steel car bodies as corrosion of the vehicles was a serious problem at the time.

“I was going to work for Ford when I graduated with my Masters degree. I passed the PhD qualifying examination, but had no money and could not live on the Fellowship,” he said. “The director of research for St Joe Lead Company, Carl Long convinced me that if I could repeat the things that I was doing with the stainless steels in lead alloys, I would be only one of a kind as opposed to the many researchers at Ford. I accepted the challenge.”

Better processes

Prengaman’s work at St Joe involved the development of rolled lead calcium tin alloys. The rolling process developed structures and rolling textures which made the material very resistant to corrosion. Delco was interested in the new material because they had such severe cracking in their cast lead antimony alloys that they were scrapping as many as a third of their battery grids. The new rolled expanded metal material did not crack and grids could be produced at 10 times the speed.

One of the benefits of the change in grid material was the fact that it did not contain antimony which was not transferred to the negative plate to cause gassing — thus maintenance-free batteries.

Apart from golf as his main relaxation, David also played in an industrial basketball league against other companies in the area, bowled, hunted, and fished.

In 1968, the 25-year-old Prengaman was introduced to Marilyn Miller by the department secretary who said that she had the perfect young lady for him. Although resisting for three years, he finally told the secretary that he would ask Marilyn out to dinner, she would hate him, then the secretary could stop bothering him.

“The day before the dinner, I was playing in the basketball league and was hit in the face breaking my glasses and cutting my face. I had 18 stitches around my eye which was very swollen and had to wear my laboratory safety glasses with sideshields to our first date.

The inauspicious start never happened. Marilyn didn’t hate him — rather the opposite! They married. They have two children, a son who is a photographer who sells his prints to galleries and calendars, and a daughter who is a chemical engineer and patent attorney.

In 1973, Prengaman moved to Atlanta to join Evans Metal. While he was there, the chief engineer from Delco visited Atlanta to meet with him and the owner of Taracorp. They made a proposal that they would build a lead rolling plant which would supply all five Delco factories with strip if Prengaman would operate the plant. He refused because at that time all the metal for the rolled grids came from primary lead and the lead calcium alloy-rolled expanded metal grids would make the lead antimony alloys which the smelter produced obsolete.

“When they turned down the offer from Delco, I was ready to look for another position. Within a week I saw an ad in a trade magazine that RSR, a major battery-recycling company, was looking for a chief engineer. Replying to the ad, I indicated that I was not interested in the chief engineer’s position, but I thought that RSR would be interested in talking to me.”

R&D at RSR

Prengaman was hired to start a R&D group and provide technical assistance to the battery customers. He spent most of the first year working with Delco to build their new rolling and expanding battery grid production lines.

“The main problem of the lead recycling process at that time was the production of pure lead which could be utilized as active materials in the battery. The impurities were too high and the refining as well as the analytical techniques to remove and analyze the impurities in the lead were not developed.”

So Prengaman and his resourceful colleagues set about developing new refining practices to remove the major gassing elements in pure lead so making it suitable for battery oxide. In addition with only AA instruments available at the time, they developed new techniques to analyze these elements in the lead at very low levels.

Necessity is the mother of invention. To extract the newly solidified lead strip from the aluminium mould, they adapted the wringer part of an old washing machine because it had rubber rolls which could grip the lead and pull it out of the mould continuously. “We called the original casting machine Maytag 1 after the most famous washing machine in the 1960s in the US,” he said.

By 1975, the RSR team had developed and introduced the first low antimony maintenance-free battery grid alloy, which could be cast on conventional grid casting equipment without cracking. It is called R275.

“In the late 1970s we set up a pilot plant to recycle the active materials in the battery by leaching and electrowinning the lead,” he said. “This produced pure lead, but improvements made to the smelting process at RSR recycling plants made the process economical.”

In the early 1980s the Environmental Protection Agency declared that the slags from the battery recycling was a hazardous waste. So Prengaman and his team developed an improved recycling process using an electric furnace to clean the slag and produce a non-hazardous product.

Towards the ALABC

In the mid-1980s Prengaman was part of a team which looked for acquisitions in Europe primarily battery recycling factories. They would acquire factories in the UK, France, Italy, Germany, Austria, South Africa, and Saudi Arabia in the mid and late 1990s. Prengaman worked to make these factories profitable and environmentally ahead of the regulations.

During the same period, Prengaman went on to develop rolled lead anodes for copper and zinc electrowinning. The anodes were based on the rolled lead calcium tin alloys which he had developed for battery grids. These anodes have become the dominant anodes for copper mines worldwide. About 95% of the mines use these anodes for recovery of copper in low cost operations by RSR and the affiliated companies of the Ecobat group which produce anodes.

In 1992 RSR and Metallgesellschaft in Germany formed a group of lead companies which joined together to form the Advanced Lead Acid Battery Consortium.

“The advanced battery consortium for the California initiative of 2% electric vehicles in five years did not include lead acid batteries,” he said. “I agreed to become the technical director of the consortium and RSR allowed me the time to spend to assure the success of the group. I still head up the ALABC.

“In the mid-1990s the vehicle profiles changed with the air now flowing over the vehicle instead of through the front grill. This caused the engine compartment to become very hot and battery life to become much shorter. In 1999 I developed an alloy called 007 which had silver added to a lead calcium tin alloy. The alloy was called 007 because the active material would “bond” to this grid compared to other alloys with silver which had to be specially treated to accept the paste.”

In 1996, Prengaman became president of RSR Technologies, Inc which provides research and development services to RSR Corporation, the European and South African Eco-Bat Group, and their customers for battery recycling.
Alongside his innovative work at RSR, Prengaman has chaired a number of committees: the North Texas Chapter of the American Society for Metals; Pb-Zn-Antimony and their Alloys subcommittee of American Society for Testing and Materials; the Lead-Zinc-Tin Committee of 1994, “Wrought lead-calcium-tin alloys for tubular lead/acid battery grids” and much more.

He has published extensively on these subjects and has served in various positions in TMS, The Electrochemical Society, Battery Council International, and American Society for Testing and Materials. He still serves as technical chairman of the ALABC, a consortium of virtually all the battery producers and lead producers throughout the world working to build improved lead acid batteries for electric vehicles.

Prengaman has received a galaxy awards: the Hoffman Memorial Prize, the Distinguished Service Award from the American Society for Metals, and the Alpha/Beta Society Award from the battery industry for his work on premature capacity loss in batteries. The Gaston Planté medal and the International Lead Award.

He has served on the EPD Council as well as membership, long range planning committees. He also was the co-editor of the Lead-Zinc ‘90 proceedings volume.

According to John Devitt, a key figure in the development of the first VRLA battery and who has known Prengaman for many years, “Dave is undoubtedly the world’s expert on lead metallurgy, plus many other metals. And he is uniquely accessible to all battery folk. He is the pioneer on many of our best alloys, so essential to a really good battery. He never fails to give a good and complete answer.”

In the course of this work, Prengaman has published more than 80 technical papers and been granted 15 patents. He has presented seminars in the, Europe, Asia, South America and eastern Europe on processes to produce improved lead acid batteries.

Ambitions

Prengaman has continued his love of golf. In 2003, he moved to a house on the Rolling Hills Golf Club course in Arlington, Texas on which he plays as frequently as possible. “My main problem is that I am afflicted with a condition called Fuch’s Distrophy which has slowly robbed me of my sight,” he said. “For the last five years I have not seen where the golf ball has gone when I hit it. Luckily my colleagues and competitors all watch the golf ball for me when I hit it.”

The Lead Pope’s current challenge is to develop a lead acid battery which is easy to produce on conventional battery making equipment, but will also compete with nickel metal hydride and Li-ion batteries for use in HEV’s as part of the ALABC programmes.

“I think that my most successful invention was the development of the rolled lead calcium tin alloys for positive grids of lead acid batteries,” he said. “The optimum alloy for positive grids was also the alloy of choice for copper electrowinning anodes. This technology is used throughout the world today to produce positive grids.

“The same alloy and rolling technique is also used in the new rolled punched battery grids used to reduce grid weight and extend battery life. The next most important was the development of a method to add calcium and aluminium to lead.”