As part of this agreement, the BYD’s e6, a 5-seat, battery-electric vehicle with the driving range of more than 186 miles (240 km) will be introduced into the Hertz China’s rental fleet making BYD’s e6 the first pure EV for rent in China. The core technology of BYD’s e6 is BYD’s internally developed lithium iron-phosphate (FE) battery technology.

The BYD e6 has been in use in Shenzhen taxi fleets for more than a year; the first fleet of 50 e6 taxis have now surpassed 2.5 million cumulative fleet miles (4 million km) without energy or range degradation and while being fast-charged daily the entire length of service, according to BYD. 300 more BYD e6s were added to these fleets in July for the 2011 Shenzhen Universiade.

On Monday, BYD reported that its first-half profit fell nearly 90% from a year earlier to 275.36 million yuan ($43 million), based on Chinese accounting standards. The Shenzhen-based company indicated earnings in the current quarter would fall by a similar amount. Its car sales, which account for nearly half its revenue, fell 23% in the first half of the year to 220,131 cars.

BYD’s share price fell 14.3% in Hong Kong trading to 16.18 Hong Kong dollars ($2.07)—the lowest finish since April 2009 and down 86% from BYD’s highest closing price of HK$85.50 in October 2009.

...Behind the plunging share price is fear that the big fall in revenue and profit from gasoline-fueled cars is damaging the BYD business model in which Mr. Buffett’s company invested: using sales of traditional cars and of the cellphone batteries BYD makes to help finance expensive research and development of electric cars, solar panels and other green technologies that have a potentially bright future.