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When I was 17, I lived in Kikwit in the Democratic Republic of Congo. It was a small rural town without running water, and you needed to have a power generator for electricity.
I got very sick because my appendix burst, so I had to undergo emergency surgery. Unfortunately, there was no fuel to start the power generator at the hospital for three days, so the operation had to be delayed. I could have died at any time.
During those three days, I decided that, if I made it, I would become an electrical engineer and lead a company that would provide electricity in places like Kikwit. Electricity saved my life, and I wanted to provide more electricity to help save lives.
Another factor that piqued my interest was the contribution of the Democratic Republic of Congo to the world as a major producer of diamond, copper, tin, tungsten and more, which are used to make electronics and modern technology. The country also has more than 50% of the world’s reserves of cobalt, which is used to make lithium-ion batteries. This made the work even more important to me.
Climate change is a global concern. In the transport sector, electric and hybrid vehicles have emerged as low-emission options to mitigate climate change, and in the power sector people use renewable energy and grid efficiency as a solution. These technologies use lithium-ion batteries for energy storage, but unfortunately they are subject to the ‘weak cell’ issue, which decreases their performance and lifetime.
Many have experienced this issue with mobile phones. When charging the phone, it shows a full charge after a short time. However, after talking for a few minutes, the battery is quickly empty.
The weak-cell issue must be solved because it increases the risk of fires, shortens the life of the battery, causes incomplete charging and decreases capacity. It can be tackled by balancing or equalising all the cells within a battery pack to the cell-voltage level. This is done with an electronic equaliser, part of the battery management system.
In the past, there were two types of equalisers to balance batteries. Passive equalisers were cheap but had poor performance, while active equalisers were expensive – 10 times the price – but had a high performance. Companies still buy passive equalisers because active equalisers are too expensive. These options were not satisfactory for lithium-ion battery packs that needed to be low-cost and last a long time.
Our solution is called the bilevel equaliser, and it is the first type of hybrid equaliser that combines both passive and active elements. The cells are grouped into sections and, within each section, passive equalisers balance each cell. The entire section is balanced by an active equaliser. As a result, the bilevel equaliser increases the longevity and performance of the battery at a low cost. We have a patent pending on the technology.
The bilevel equaliser is a game-changer. Experiments have shown that it increases the discharge capacity by more than 30%. It is most beneficial in large lithium-ion battery packs such as those found in electric vehicles, aerospace, power grids and renewable energy.
The bilevel equaliser can be built from scratch, and we have also developed a retrofit kit that can convert passive equalisers to bilevel equalisers. As the traditional battery pack ages, it becomes more unbalanced and the discharge capacity decreases. The bilevel equaliser could correct that. It is especially beneficial for second-life batteries.
The next step is to field-test the bilevel equaliser, and then bring it to the market.
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.