UPDATE 1-Samsung SDI Q2 up 33 pct, sees smartphone boost

* Q2 net profit 68.4 bln won, above 66.2 bln forecast

* Sees battery demand growing around 20 pct in H2

* Shares down 1.1 pct following results (Adds details)

SEOUL, July 27 (Reuters) - Samsung SDI Co Ltd 006400, the world's No.2 rechargeable battery maker, said its second quarter profit rose by a third, as strong sales of smartphones and other electronic gadgets boosted by demand for its products.

Samsung SDI expected demand for lithium ion batteries to rise by around 20 percent in the second half thanks to strong growth expected in the smartphone market.

Demand for plasma display panels is seen growing 14 percent from the first half driven by rising sales of 3D TVs, Samsung SDI said in a statement.

The maker of lithium-ion batteries for mobile phones and plasma display panels for TVs reported a 68.4 billion won ($57.4 million) net profit for the three months ended June against a 51.4 billion won net profit a year earlier.

The company, which competes with Japan's Sanyo Electric 6764.T in battery and LG Electronics (066570.KS) in plasma panels, had been expected to report a net profit of 66.2 billion won based on averaged estimates from 13 analysts surveyed by Thomson Reuters I/B/E/S.

Samsung SDI and its 50 percent owned subsidiary, Samsung Mobile Display, sell rechargeable batteries and AM-OLED (active-matrix organic light-emmitting diode) displays to Nokia (NOK1V.HE), Samsung Electronics (005930.KS) and Apple Corp (AAPL.O).

Global shipments of smartphones are seen growing about 50 percent in the second half of 2010. That will help drive demand for its high-end OLED displays. [ID:nTOE64J08D]

Analysts see margins picking up for Samsung SDI on booming sales of smartphones and new digital gadgets such as Apple's iPad tablet PCs.

The South Korean government said its investment together with the private sector for rechargeable batteries will reach 15 trillion won by 2020. [ID:nTOE66B037]

But there remains concerns about oversupply of rechargeable batteries and questions about demand in the next three to six months.

Samsung SDI shares fell 1.1 percent to 175,000 won by 0440 GMT. (Reporting by Suh Kyung-min; Editing by Lincoln Feast)