Wednesday's spacewalk saw Cassidy and astronaut Dave Wolf replace only two batteries instead of the four 170-kg batteries that had been planned. That work was cut short due to the spacesuit problems.

Each solar panel on the station has six batteries, which were designed to be changed after six and a half years. Because they are so large the work must be done while NASA is still operating the space shuttles that are capable of carrying large loads, the space agency said.

A fifth and final spacewalk is planned for Monday, when astronauts will put a video camera on the Japanese Kibo laboratory's new porch, which was installed earlier in the mission allowing experiments to be exposed to the extremities of space.