Susan J. Ellis, 70, of Wynnewood, an internationally known expert who helped develop the field of volunteer management through her firm, Energize Inc., in Philadelphia, died Sunday, Feb. 24, at Hospice House at Ridley Park after an eight-year battle with cancer.

Ms. Ellis was considered the doyenne of the volunteer management specialty, which promotes volunteerism and trains and supports those who lead volunteers.

In 1977, when she founded Energize Inc., there were few resources for those hoping to become professional managers of volunteers and seeking to stay well-versed in the field.

Seeing an opportunity, Ms. Ellis created a business that offered training, consulting, publishing, and, later, resources and services online. With Ms. Ellis as its president, the business assisted clients in profit and nonprofit enterprises around the world.

“One of the reasons volunteer management is even on the radar is because of trailblazers like Susan,” said Sheri Wilensky Burke, a Philadelphia-based volunteer management and training consultant, who began working with Energize in 2015.

One of Ms. Ellis’s strengths was her writing. She wrote or co-wrote 14 books, including From the Top Down: The Executive Role in Successful Volunteer Involvement; By the People: A History of Americans as Volunteers; and The Volunteer Recruitment (and Membership Development) Book.

From 1981 to 1987, she was editor in chief of the Journal of Volunteer Administration. She wrote more than 120 articles on volunteer management and was responsible for the bi-monthly column, “On Volunteers,” in the national NonProfit Times from 1990 to 2015.

When new technology emerged, she launched a website for Energize in the mid-1990s. The website was embraced by volunteer program leaders around the world. “She was absolutely fearless in the face of new innovations,” said Jayne Cravens, co-author with Ms. Ellis of The LAST Virtual Volunteering Guidebook.

In 2000, Ms. Ellis and colleague Steve McCurley launched the field’s first online journal, E-Volunteerism: The Electronic Journal of the Volunteer Community. The two were its editors. Since 2005, she had been the dean of faculty for Energize’s Everyone Ready Online Volunteer Management Training Program. It does not confer a degree.

Ms. Ellis helped foster volunteer management associations and spoke at launches of such groups in Japan, Singapore, the Netherlands, and Ecuador.

The only child of Ernst and Anne Ellis, Ms. Ellis grew up in Irvington, N.J. She moved to Philadelphia to enroll in Temple University. After graduating from Temple’s College of Arts and Sciences in 1969, she accepted a job with a community volunteer program in Philadelphia Family Court.

She fell in love with the program’s volunteers and soon found her life’s calling: to professionalize the field of volunteer management.

Ms. Ellis was recognized with the Young Alumni Diamond Excellence Award from Temple, and the Association for Volunteer Administration’s 1989 Harriet Naylor Distinguished Member Service Award.

Before she died, she established the Susan J. Ellis Foundation to support education and research activities in volunteerism, and prepared her staff and consulting team to continue the many facets of Energize without her.

Consultant Rob Jackson met Ms. Ellis decades ago at a conference and they developed a pattern of monthly Skype calls from his base in the United Kingdom. “When I think of Susan, I think of those monthly calls,” he said. “I think of the fun we had writing and presenting workshops together.”

Ms. Ellis enjoyed science fiction including Star Trek, unicorns, theater, animated films, and Philadelphia folklore.

Friend Kathy Gardner recalled the biannual gatherings for friends that Ms. Ellis hosted at her home. “When we gathered at Susan’s home, we were family,” said Gardner. “Her genuine warmth and welcoming spirit, her wonderful laugh, and her sense of the absurd drew us together in harmony.”

There were no immediate survivors. Services are private.

Memorial donations may be made to the Susan J. Ellis Foundation, Energize Inc., 5450 Wissahickon Ave., C-13, Philadelphia, Pa. 19144.