This sent the company's market capitalization down to HK$41.1 billion, down HK$20.9 billion from about HK$62 billion at the opening of trading today.

Chinese power battery giant CALB, which went public only 20 days ago, plunged in Hong Kong today, losing tens of billions of Hong Kong dollars in market value as an arrangement to stabilize its share price is set to expire tomorrow.

CALB fell 34.58 percent to HK$22.80 in Hong Kong by the end of trading today, the biggest one-day drop since its October 6 initial public offering (IPO).

That sent the company's market capitalization down to HK$40.4 billion, down HK$21.6 billion from about HK$62 billion at the opening of trading today.

There is no apparent negative news about the company yet.

It is worth noting, however, that CALB's Greenshoe Option, or Over-allotment Option, granted to underwriter Huatai Securities will expire tomorrow, and investors' concerns about the impending disappearance of the stabilizing force on the stock price may have fueled today's sell-off.

The Changzhou, Jiangsu-based company raised about HK$10.1 billion in its Hong Kong IPO at HK$38 per share, which was at the bottom of the HK$38 to HK$51 offer range.

CALB announced the offering results on October 5, showing that investors subscribed 0.21 times in the public offering.

Fifteen cornerstone investors, including Xpeng Motors and Tianqi Lithium, subscribed for a total of about HK$5.8 billion of the company's shares, representing 8.43 percent of the post-IPO equity.

The company's shares began trading in Hong Kong on October 6 and closed the day flat at HK$38 per share.

Shares of CALB's main competitor CATL, which trades in Shenzhen, also fell today, but by only 2.68 percent.