(?over-unity?) UT's bilevel equalizer prolongs pack life (v)

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(?over-unity?) UT's bilevel equalizer prolongs pack life (v)

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University of Toledo engineer finds power from near-death experience
March 10, 2018 Jay Skebba

[images  / Kurt Steiss






video  flash
VIDEO: Ngalula "Sandrine" Mubenga

    Ngalula "Sandrine" Mubenga nearly died as a girl in Africa because of a
hospital's lack of power, and has developed a new energy storage solution to
make battery packs in electric vehicles, satellites, planes and grid
stations last longer and cost less.

University of Toledo electrical engineer Ngalula "Sandrine" Mubenga says her
near-death experience 20 years ago was scary but also helped spark new
technology that could save lives.

Ms. Mubenga, assistant professor of electrical engineering, recently
developed a bilevel equalizer to prolong battery life in electric vehicles,
planes, and grid stations.

When Ms. Mubenga was 17, she was hospitalized in her hometown of Kikwit in
the Democratic Republic of the Congo. She needed surgery to remove her
appendix, but the hospital was without power. The city had no fuel,
rendering the hospital's generator useless.

After three days of waiting, Ms. Mubenga finally had the procedure.

"That experience in the hospital is what gave me my motivation to be an
electrical engineer," Ms. Mubenga said. "I was really scared for my life; I
could have died at any time. So I wanted to become an engineer and learn as
much as I could about renewable energy to bring electricity to places like

The project started in 2015 after UT engineering professor Tom Stuart gave
Ms. Mubenga the idea for the bilevel equalizer. Ms. Mubenga was working on
her PhD at the time, and Mr. Stuart was her adviser.

Ms. Mubenga quickly realized the task wasn't going to be easy. She
demonstrated plenty of trial and error — and patience.

"It was freakin' tough," she said. "It's one thing to do it on a piece of
paper, it's another to simulate it on the computer. When you get down to the
prototype and actually build it and test it, this is when you really see
things happen."

On several occasions, the design and computer simulations appeared fine, but
then sparks flew when Ms. Mubenga flipped the power switch. The mechanism
has dozens of wires and other components, and if just one malfunctions, it
throws off the entire attempt.

Ms. Mubenga kept a few failed parts as reminders of how far she's come.

"Some are completely black from being burnt," Ms. Mubenga said. "And of
course, there's nothing on Google about it or in your books. You have to
figure it out."

The technology is the first to combine an active equalizer with a low-cost
passive equalizer.

Manufacturers today balance cell voltages in a large battery pack, usually
with a passive circuit which loses more energy. Active circuits are more
efficient, but cost 10 times more.

Lithium ion batteries continue to drop in price, but most have a weak cell
issue. One weak cell can compromise the entire battery, and the typical
electric vehicle has hundreds of cells.

Ms. Mubenga's method groups the cells into sections. Each cell is balanced
with a passive equalizer, and the whole section is balanced with an active
equalizer. The bilevel equalizer extends battery life by about 30 percent.

"It could be huge," Mr. Stuart said. "There are several applications for
this, but the obvious one is electric vehicles. One that is even much bigger
is electric utilities are starting to use these batteries."

UT owns the patent on the new technology. Ms. Mubenga said the next step is
to incorporate the bilevel equalizer into hybrid and electric vehicles and
energy storage grids outside the lab.

She hopes to eventually sell her creation to manufacturers.
[© toledoblade.com]
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