The shuttle's departure broke up the biggest off-the-planet gathering ever: 13 people altogether in space.
NASA takes it slow and steady as team installs batteries.
NASA begins 202nd spacewalk by Americans since the Apollo 11 lunar excursion.
Endeavour is poised to take off for the space station Wednesday evening, along with seven astronauts. Forecasters put the odds of good weather at 60 percent.
Mission has been scrubbed twice by hydrogen leak; now weather may delay launch.
Saturday night's planned launch is already a month late – and could be delayed until late July if storms persist.
Stormy weather could stall this weekend’s launch of space shuttle Endeavour. Forecasters on Wednesday put the odds of acceptable weather at just 40 percent for a Saturday evening launch. Conditions improve only slightly on Sunday.