Enova Systems Inc. on Wednesday said that it expects to report third and fourth quarter revenue that is “materially below” what it saw in the first half of this year.

The Torrance developer of hybrid electric and all-electric drive systems and system components for vehicles said its two largest customers are reducing orders, which it blames on current economic uncertainty slowing sales of alternative energy vehicles.

The company has potential lucrative contracts with electric-truck manufacturers, but sales of those vehicles have slowed truck and bus fleet operators have held off on converting to electric vehicles. Enova said that it is considering a variety of ways to reduce “purchasing obstacles” with its major customers. The company also is in advanced discussions with potential new customers in Asia and the United Kingdom.

In its latest quarterly filing with the SEC last month Enova reported cumulative losses totaling about $147 million dating back to its development years in the 1990s.

Shares were down 1 cent, or less than 5 percent, to 25 cents in midday trading on the NYSE Amex.