More than 200 Lenovo F41 laptop users have demanded the Chinese computer maker replace their faulty batteries.

Most of the customers bought the laptops after March 2008, and the problematic batteries were provided by Sony and made in Japan, the Beijing Times reported.

The newspaper said about 270 people joined an online forum and demanded Lenovo replace the batteries, because the warranty period had expired.

The members complain that the batteries run out of power in about 20 minutes.

Some members said the battery died when the battery management system showed there was still 70 percent energy left.

"I bought my laptop in May 2008, and in June, I found my laptop would switch off if it showed there was still 50 percent energy left," Wan Zhengpeng, a 20-year-old student from the Chinese Agriculture University, told Metro yesterday.

"I keep running down and recharging the battery completely every month as Lenovo advised, but it did not make my battery work as long as it should," he said.

Lenovo and Sony were not available to comment yesterday.

A Lenovo spokesperson told the Beijing Times that the company had received complaints from more than 60 users. They sent two batteries for testing to Sony headquarters in Tokyo on Oct 30.

They promised to provide new Sony batteries for the 60 users who complained.

The Lenovo F41 computers hit the market in the second half of 2007, and sold about 2 million units.

The spokesperson told the newspaper that the current complaints were not a common problem.

It was reported that three brands of batteries were used in the model, but the other two brands of battery were not faulty.

In August, Lenovo recalled Thinkpad laptops because its Sony batteries were too hot while in operation.