What happened 

Shares of battery maker EnerSys (NYSE:ENS) fell 10.9% in May, according to data provided by S&P Global Market Intelligence, after reporting guidance that left a lot to be desired. 

So what 

Fiscal fourth-quarter results were released at the end of the month, and they weren't actually that bad. Revenue was up 3% to $626.8 million, and net income rose from $22.8 million a year ago to $33.8 million, or $0.76 per share. But it's full-year results that investors were worried about. 

Batteries stacked up.

Image source: Getty Images.

What sent the stock lower was management lowering guidance for the full year. CEO David Shaffer said he expects $1.10 to $1.14 per share in earnings for fiscal 2018, rather than the $1.21 to $1.25 given in previous guidance. Price increases are taking longer to implement, and higher commodity costs are weighing on results. 

Now what 

The challenges EnerSys is facing are partly out of its control on the commodity side. And I'm not sure how price increases will work out for the company long term in an industry that's seeing a rapid decline in battery prices. The other concern is that EnerSys trades at a pretty lofty price-to-earnings multiple of 21 with very little growth. After the disappointing guidance, I just don't see the future of this battery company getting brighter soon.