By Ben Klayman

CHICAGO (Reuters) - Energizer Holdings Inc (ENR.N: Quote, Profile, Research), known for its namesake batteries and Schick razors, posted a lower-than-expected second-quarter profit on Tuesday as the weak U.S. economy hurt its battery business, sending shares down 18 percent to their lowest level in more than a year.

The company said the rest of its 2008 fiscal year will be challenging, but the outlook for 2009 and beyond is positive.

SunTrust Robinson Humphrey analyst William Chappell Jr. said he was disappointed with the results, but the share price decline was a buying opportunity.

"We are obviously disappointed with the results, but believe a large part of this was built into the stock and the company should rebound to more normalized earning performance as the Playtex acquisition is digested," he wrote in a research note.

Chappell added battery inventories at retail are now stable, revenue from the Playtex personal-products business acquired last year was healthy and the benefit from lower zinc costs should begin to appear in the third quarter.

Net income for its second quarter that ended March 31, fell 8.6 percent to $60.9 million, or $1.03 a share, from $66.6 million, or $1.14 a share, a year earlier.

Excluding one-time items, it earned $1.10 a share, far short of analysts' average forecast of $1.41, according to Reuters Estimates.

"While we knew that the second quarter would be challenging, the modest decline in the U.S. battery category combined with the magnitude of the trade inventory de-stocking by retailers was unanticipated," Chief Executive Ward Klein said in a statement. "We believe that the category decline was related to sluggishness in the U.S. economy."