Renewable energy storage of the future? Battery recycling for India

Three years ago, a brilliant idea occurred to Prodip while he was at work: “Many companies replace their employees’ laptops every three years. I thought that there must be some way to do something useful with the retired laptops. The batteries are there, and they still work — we just need to do something with them.” The idea that would later lead to the startup Nunam (Sanskrit for “for the future”) is born.

Together with co-founder Darshan Virupaksha and other kindred spirits, he has been working on the creation of a renewable energy storage system since 2017. They carried out the initial experiments with old phone batteries. Since 2019, they have been working on systems using retired laptop batteries, which are converted into new, mobile energy storage and charging stations.

In the following months, the pilot project will begin with street vendors in India. That means it’s time to talk with Prodip: about where they get their used batteries, what the energy storage systems will be used for, and why they developed an app for it.

Can you tell us more about your pilot project for sustainable sources of energy for the street vendors in India?
Prodip Chatterjee: We have developed prototypes for two use cases. The energy storage systems are about the size of a car battery and weigh two kilograms. In our pilot project, vegetable vendors use the mobile energy storage systems so they can light their stands after dark, which allows them to stay open for business. Aside from that, they can also charge their phones.

We envision the second use case for users in their homes. In India, there are three devices that are especially important: smartphones, lamps, and fans. And our renewable energy storage unit can power an LED light, for example, for six hours.

Building a renewable energy storage unit... that sounds complicated. Where do you get the batteries?
We get the lithium ion batteries and rechargeable batteries from local scrap dealers around Bengaluru and other cities. We remove the cells from the old batteries and test them. The average remaining battery capacity is about two-thirds of the original capacity. It’s really crazy to think about how much potential just lands in the trash.

In addition to that, we also look at parameters such as heat development, internal resistance, and more. If — and only if — the batteries meet the necessary criteria, we install them in the new energy storage units.

Would it be correct to picture the energy storage unit as a sort of power bank?
No, it’s significantly larger. A power bank usually has eight cells. Our renewable energy storage units have at least 40 cells; the larger prototype has 120. We want them to be able to supply energy to businesses or street vendors, and that requires a bit more power. But the technology and ports are equivalent to a power bank.

What about a circular economy? At some point the batteries will really be empty. How do you get the energy storage units back so that they don’t end up in the trash again?
I still see that as a major challenge. We have developed a few different approaches to solving that problem: first of all, each cell has its own ID with a QR code. So we always know where the energy storage unit with that particular cell is and what condition the cell is in. We developed an app and an online dashboard to track them. This allows us to use the usage data to predict how long the storage unit will remain usable. When the capacity begins to decline, we write to the buyer and arrange an exchange. Staying in close contact with the customer will be the critical factor in preventing the storage units from landing in the trash.

Secondly, we’ve considered offering a rental model in addition to the sales model. That means that the energy storage units have to be returned after a certain period of time.