Translation of the Dutch text by Romy Veul |  Photo: Barbra Verbrij Fotografie |  11 November 2026

Let’s save our batteries, for our wallet and for our world. This slogan appears alongside the product that started it all for Jardo Stammeshaus: Leo. In 2021, he graduated cum laude from VU Amsterdam with a Master’s degree in Physics, having written a literature review on battery degradation. That research laid the foundations for the company he now runs from the VU StartHub.

It all started during your Master’s studies. You were pursuing two Master’s degrees at the same time at VU Amsterdam. Why did you decide to do that?
‘After completing my Bachelor’s degree in Physics at the University of Amsterdam, I was torn between two Master’s programmes at VU Amsterdam: Physics, and Science, Business & Innovation. I found physics fascinating, but I also wanted to do something involving entrepreneurship and sustainability. In the end, I decided to pursue both degrees.

During my Bachelor’s, I had already learnt to give everything I do two hundred per cent. I wanted to become a world boxing champion and trained eight times a week, for around sixteen hours in total. So working hard towards a goal was nothing new to me.’

But you didn’t continue competing at the highest level. Why was that?
‘While finishing my Bachelor’s degree, I became the Dutch national student boxing champion. Unfortunately, I subsequently suffered a nerve injury in my arm, which meant I could no longer box or kickbox. I was absolutely gutted. It also meant that I suddenly had an extra sixteen hours a week on my hands. I decided to devote that time to my studies and my interest in sustainable entrepreneurship.

I completed both Master’s degrees and was even named Student of the Year at VU Amsterdam. Part of the award included mentoring from an entrepreneurship coach, which proved incredibly useful in developing my business idea further.’

'At some point, I thought: why isn’t there a single device that takes care of all this automatically?’

How did you come up with the idea for Liion Power during your studies?
‘It started with a problem I kept running into myself. I’ve always taken good care of my electronic devices, yet I still had to replace them regularly. The reason was always the same: a worn-out battery. Surely there had to be a better way, I thought.

So I started researching how to make batteries last longer. While studying battery degradation, I discovered just how much the way you charge a battery affects its lifespan. I then began using all sorts of tools to charge my devices more intelligently: a timer to delay charging my phone until night-time, a slower charger for overnight charging and a fast charger for during the day. At some point, I thought: why isn’t there a single device that takes care of all this automatically?’

And you decided to develop that device yourself?
‘Yes. During a course called Entrepreneurship for Physicists, I was given a month to develop a business idea. Afterwards, I was able to work on a prototype through VU Amsterdam’s Demonstrator Lab.

But then the COVID-19 pandemic struck. There I was, sitting in my student room with ambitions to conquer the world. I needed a laboratory and knowledge of electrical engineering, but because of the pandemic, I had nowhere to go. So I decided to take an online electrical engineering course to keep making progress.

For weeks, I spent every day soldering in my bedroom, with the window permanently open to let the fumes out. Looking back, those weeks taught me an enormous amount. When VU Amsterdam reopened, I was able to continue working on my prototype in the electronics lab.’

'If you believe something is impossible, you won’t get anywhere'

How did that first prototype grow into a company?
‘We entered the prototype in pitch competitions and won several prizes, including €100,000 in the Postcode Lottery Green Challenge. We also received a research and development grant. That gave me enough funding to develop the technology further, and Liion Power was born.

One thing I learnt at VU Amsterdam, and experienced first-hand throughout that process, is that entrepreneurship is all about constantly solving problems. If you believe something is impossible, you won’t get anywhere. You just have to get started, work out what needs to be done and keep taking the next step. And that’s exactly what we’re still doing now, a few years down the line.’

Your first product, Leo, has now been on the market for two years. How does it work?
‘Leo is a smart USB charger that charges the batteries in consumer electronics, such as phones and headsets, more intelligently and sustainably. This can extend the lifespan of the battery, and therefore the device itself, by up to fifty per cent. You simply plug Leo in and leave it to do its job; it takes care of smart charging automatically. For people who want more insight, there’s also an app that allows them to view things like their charging history.

You can compare a battery to a balloon. If you keep inflating a balloon to its maximum capacity, the rubber is constantly under strain, causing it to wear out more quickly. Batteries work in a similar way: when they are charged to full capacity and remain fully charged for long periods, chemical stress and heat build up. This accelerates wear and tear.

We’re now working on getting Leo onto shop shelves. To do this, we’re collaborating with 123accu.nl, a specialist in batteries, chargers and replacement products for laptops, phones, tools and other devices. Our product is also now available through Mediamarkt.nl and bol.’

'In the future, there could be fifty or even a hundred products from different brands using our technology'

Liion Power has now won innovation awards in Las Vegas and Berlin. What does that mean to you?
‘I’m absolutely delighted with awards like these. We have a growing team of people who bring a wealth of knowledge and experience to their work. Winning an award at such a major event is an enormous recognition of everyone’s efforts.

After winning the award at the CES trade show in Las Vegas, we also received a great deal of media attention. I was subsequently invited to give a talk to the Committee for Entrepreneurship. I also had a fifteen-minute one-to-one conversation with Queen Máxima about ambition in entrepreneurship, which was a very special experience.’

What does a typical working week look like for you as an entrepreneur?
‘As CEO, I do everything we don’t have a dedicated employee for. I manage the technical team, but I’m also involved in marketing, sales, finance and legal matters. During the week, I work twelve to fourteen hours a day. That might sound like a lot, but I absolutely love what I do. The mindset I developed during my years as a competitive athlete – always giving everything two hundred per cent – still serves me well.’

Where do you hope to be in five years’ time?
‘Our goal is to work with major manufacturers to integrate our technology into all kinds of electronic devices. Right now, we have one product of our own on the market. In the future, there could be fifty or even a hundred products from different brands using our technology.

Above all, I hope to keep doing what I love. It’s still remarkable to think that my own charging problem became the foundation for a company that is now steadily gaining ground, both in the Netherlands and internationally. We hope to make an even greater positive impact on sustainability in the Netherlands and around the world in the years to come.’