* Q3 net 4.6 mln yuan vs 77.4 mln yuan yr ago
* BYD forecasts up to 98 pct drop in FY earnings
* BYD's auto, solar panel and cell phone businesses declining
BEIJING, Oct 29 (Reuters) - BYD Co Ltd , the Chinese carmaker backed by billionaire investor Warren Buffett, reported a 94 percent slide in third-quarter net profit due to a slumping domestic market and its money-losing solar energy business.
In a stock exchange filing, BYD forecast a 92 to 98 percent fall in its full-year earnings due to sluggish auto demand. The performance of its cell phone assembly business will also decline, while its solar panel sales will plunge due to the euro zone debt crisis, the company said.
In July-September, BYD posted a net profit of 4.6 million yuan ($736,100). That compares with 77.4 million yuan a year earlier when it benefited from a surge of more than 580 percent in returns from investments that the company did not specify.
In the first nine months, net profit fell 94 percent to 20.9 million yuan, in line with its own forecast of a 75-95 percent decline.
BYD did not release data on vehicle sales in the first nine months or the third quarter.
"The company's auto sales volume is set to decline for two consecutive years," said Yankun Hou, head of China Research for Asia Autos and Auto Parts for UBS, maintaining his 'sell' rating.
BYD, like most Chinese car makers, benefited little from a fall in demand for Japanese cars following a rise in anti-Japanese sentiment caused by a diplomatic dispute between the two countries.
Many consumers have turned to German, Korean or American brands, which are perceived as superior to Chinese models in quality, analysts say.
BYD's Hong Kong-traded shares, which have lost about 7 percent since the start of the year, rose 3.6 percent ahead of the results on Monday. The Hang Seng Index fell 0.2 percent.
Chairman Wang Chuanfu has said BYD is expected to see a return to profit growth by 2013 when an internal restructuring is completed. The company said previously it will streamline its sales network to improve margins. ($1 = 6.2489 Chinese yuan) (Reporting by Fang Yan in BEIJING and Kazunori Takada in SHANGHAI; Editing by Ryan Woo)