The Story Behind the Solar DC PCU: How I Invented India's First 12V/120W Solar DC Power Conditioning Unit

The Solar DC PCU story starts with a government project that got dropped. TEDA — the Tamil Nadu Energy Development Agency — came to us with a concept: small DC-powered homes for rural communities. The idea was simple and powerful. Solar panels generate DC. Batteries store DC. Lights and fans in a basic home do not need AC conversion at all. Run DC appliances directly from panels and battery, eliminate the inverter, reduce cost and losses. We started developing the technology. A 12V, 120W Solar DC PCU — enough to run lights and a fan in a modest home. Then TEDA dropped the project.

UPNEDA Said Yes — 50,000 Homes

We did not give up on the technology. We went looking for another partner. The Uttar Pradesh New and Renewable Energy Development Agency — UPNEDA — was open to it. UP had some of the worst power cuts in India. Rural households were spending heavily on kerosene for lighting. A 12V/120W Solar DC PCU that could run lights and a fan the entire night on a small battery was exactly what the state needed.

The BLDC Fan Challenge Nobody Had Solved

The biggest challenge was the fans. A 120W DC system cannot power a conventional AC ceiling fan. The answer was BLDC — Brushless DC — motors. A BLDC fan runs directly on DC, consumes a fraction of the power of a conventional fan, and lasts far longer. The problem: nobody in India had heard of BLDC technology for ceiling fans at that time. There were no manufacturers, no supply chain. We developed the motor control technology in-house and worked with a fan manufacturer to bring it to production. Su-Kam became one of the first companies in India to develop and deploy BLDC fans at scale — years before BLDC became the standard it is today.

Getting DC lights manufactured was also a challenge at that time. Everything had to be developed, sourced, and standardised from scratch.

The Patent: Grid-Integrated MPPT

As the Solar DC PCU matured through the UPNEDA deployment, we kept improving it. The most important addition was grid integration. A purely solar-and-battery system has one critical weakness: consecutive cloudy days drain the battery dangerously. For a rural UP family, a dead battery meant no light and no money to replace it.

Our solution: integrate the grid as a battery guardian. The moment battery voltage dropped below a set threshold, the grid charger would activate — not to run the load from the grid, but purely to protect the battery. It would bring the battery back up to a safe level, then hand control back to solar. The DC lights and fan kept running throughout. The system was never down. Battery life extended dramatically because deep discharge events were eliminated.

Discovery Channel Came to Film It: Sun Fuel

The scale of the UPNEDA deployment did not go unnoticed. Discovery Channel came to India to document it. The resulting documentary — Sun Fuel — covered the 50,000-home project: the families, the technology, and the story of how an Indian company built and deployed solar home systems at a scale few countries had matched.