Competition in China's power bank rental services sector is starting to heat up and could become the next big thing. At least 15 start-up firms have recently joined the sharing-economy business model, while three others landed on a Series A round of funding worth hundreds of million yuan.

Tech giant Tencent and Hangzhou Vision Capital Management also led a Series A financing for Xiaodian, raising a total of $14.5 million. Other investors include CDH Investments, GSR Ventures, DT Capital Partners, and In Capital. Start-ups like Hidian have also raised financing by giving priority to the niche market of power bank rental.

So how does the power bank rental service industry work?

Laidian Technology allows users to rent power banks from one station and they can return it to another station, or whichever is nearest. This scheme is available in train terminals, airports, and hospitals.

Ankerbox, on the other hand, caters to smaller places such as coffee shops, café, and bars. Their power banks are movable. Meanwhile, Xiaodian has their power banks installed on desks and can be installed in public areas like restaurants, KTVs, and subways.

In all three options, smartphones are charged after scanning a QR Code and paying online. Generally, the first hour is free, and the succeeding time cost 1 yuan ($0.14) per hour.

Currently, the profits of power banks come from rentals, deposits, and advertising revenue. Although their prices are relatively low, it is still attracting the interest of investors considering that China alone has at least 700 million smartphone users.

"It's the same with the bike-sharing system, we must provide a certain scale of shared power banks at first, so as to change people's habits of renting power banks," Tang Yongbo, Xiaodian's founder, said.

Meanwhile, "sharing-economy" has been making a buzz in China over the past two years, covering rental of almost everything, including bikes, cars, apartments, to name a few. The sharing economy is slated to reach $300 billion and could see an annual growth of 40 percent over the next five years.