What happened

Shares of Plug Power (PLUG -6.95%) were down 2.9% at 3 p.m. EDT on Friday, with no apparent bad news for the fuel cell company.

Chances are, however, today's decline has to do with the success of its rival in fuel cells, Ballard Power Systems (BLDP -2.68%).

Cartoon fuel cell car on palm of hand putting out H2 bubbles as exhaust

Image source: Getty Images.

So what

In contrast to the lack of news at Plug (aside from Seaport Global Acquisition's optimistic buy report on the stock yesterday), Ballard stock has been on a bit of a roll lately, and the company's public relations office may be sucking all the oxygen (and investor attention) out of the room.

Over the past week or so, Ballard has announced:

  • A big sale of 15 70-kilowatt FCmove fuel cell modules to Tata Motors to power the latter's electric buses.
  • A sale of two 200-kilowatt fuel cell modules to Siemens Mobility, designed to power the latter's two-car Mireo Plus H passenger train on a trial run in Germany.
  • The release of its second-quarter results on Friday, Aug. 6.

Now what

Ballard is on a roll, and if investors have only a limited supply of money to invest in the fuel cell sector, it could simply be that this week, they're investing it in the stock that appears to have momentum -- Ballard -- leaving Plug Power in the lurch.

Is that the right decision? We'll find out when Ballard reports, and we'll see precisely how much better its business is doing than Plug's.