Astronauts work on battery equipment inside space station today. Photo: NASA TV/Spaceflight Now

In what is becoming a fairly common occurrence, engineers in Russia are troubleshooting apparent problems with one of the eight batteries aboard the international space station's new Zvezda command module.

What is causing the problems is not yet clear. But even if the battery in question is lost, officials say, Zvezda will have more than enough power to support the lab's first full-time crew starting in November.

And that assumes the crew of a shuttle assembly flight next month does not replace it or store a spare on board before the station crew gets there.

"Even if it turns out we don't recover this battery, we'll have seven fully functional batteries by the time the crew arrives," space station flight director Mark Ferring said early today.

"Seven batteries is way more than we need for the crew at this point," he added. "If we do have a problem recovering this right now, we don't consider that an impact at all."

The Atlantis astronauts, meanwhile, spent the day moving more supplies and equipment into the station from the shuttle and a docked Progress supply ship, installing a replacement battery in the Russian Zarya module as planned and two battery charge controllers in Zvezda.

The astronauts also installed an electronic device in Zvezda that will be used to control battery charging in visiting Progress and Soyuz spacecraft.

Four bags of fresh water, generated by the shuttle's electricity producing fuel cells, were transferred into the station, along with exercise equipment, a peg board-type tool panel and equipment to enable future crews to shoot large-format IMAX movies.

Before going to bed, the astronauts planned to connect a hose and a waste holding tank to the space station's toilet. They also planned to fill the toilet's tank with water from the shuttle, but no valves will be opened to actually "wet" the system until the full-time crew arrives in November.

Sharon Castle, the STS-106 launch package manager, said 1,900 pounds of equipment and supplies have now been transferred from the shuttle to the station and another 489 pounds of gear has been moved from the station to Atlantis for return to Earth.

"The orbiter's in great shape and the crew is doing great," said lead flight director Phil Engelauf. "They got out into the station this morning about 25 or 30 minutes ahead of the scheduled time and immediately jumped right into the installation activities and have stayed pretty much ahead of the timeline the whole way."

The international space station docked to Atlantis. Photo: NASA TV/Spaceflight Now

Along with moving equipment into the space station, the astronauts also used the shuttle's maneuvering jets to boost the station's altitude by about 3.5 miles. This was the second of four planned reboost maneuvers. When the shuttle departs, the station should be left in a circular orbit 235.8 miles high.

"We finished yesterday's crew activities in very good shape, we were a little bit ahead on the Progress unstow and we were quite a ways ahead on the shuttle part of the transfers compared to what we had estimated the crew would be by that time," Engelauf said.

"And we continued on today in that same fashion. We're looking at the ability to possibly add a couple of tasks to the flight that we didn't have on the list to begin with."

Those items include a search for fungus growing behind panels in the Russian modules, work to stow equipment currently stored in the Zvezda module's two staterooms and filling the toilet's tank with water.

"A lot of these are relatively secondary in nature," Engelauf said. "We're already installing the tank and the hoses on the toilet. Now we're going to collect some of the water from the shuttle and fill that to mix with the (waste) preservative that's in there as part of getting the toilet set up to operate."

As for the search for fungus, "there's a lot of concern as we leave the vehicle closed up for a long period of time that any bacteria or fungus that are growing in there will have a chance to multiply," Ferring said.

"And even though we didn't find anything on STS-101 (a shuttle visit in May), our Russian counterparts are very interested in having us go in there and look behind some panels and do a little bit of cleanup in those areas."

The station's toilet continues to get quite a bit of attention in the media. And even aboard the space station.

Shuttle pilot Scott Altman, taking flight controllers on another video tour of the Zvezda module, showed off the station's bathroom today, saying the Russians equipped it with "all the facilities, everything you need, including a mirror on the wall for doing that morning shave and getting ready to go, brushing your teeth and washing your hair."

Pulling a curtain across the door, he added: "There's a privacy door on the bathroom, obviously, to make sure everybody can have their own moments alone."

The toilet will not be used or even tested during Atlantis's flight. The space station's first crew will complete the potty's activation and use it for the first time.

ISS toilet. Photo: NASA TV/Spaceflight Now

"It's much like you'd find on a camper or out on a boat," said William Shepherd, commander of the station's first three-man crew. "This one's a little bit different, though, because it's got airflow and that keeps all the wastes going in the right direction.

"We have a container below the toilet and when we're finished, every once in a while we take these containers, put them in our cargo vehicles and send them back to the surface of the Earth."

The space station's battery problems continue to be a concern, albeit a relatively minor concern at this point.

Battery No. 5 in the Zvezda module was activated for the first time Wednesday. During subsequent passes over Russian ground stations, engineers noticed "some funny signatures," Ferring said, "and it's not clear it's charging normally."

"The experts in Moscow have been analyzing the situation and it's inconclusive," he said. "We have the potential that battery number five will not be operational."

Batteries are critical components on the station, storing power from its solar arrays for use when the complex passes into Earth's shadow. The station spends roughly half of each 92-minute orbit in darkness.

But the Russians have had frequent problems with their space station batteries and associated control devices. Partly due to age, partly due to charging problems, four of the Zarya module's batteries were replaced during a shuttle visit in May and two more have been replaced during Atlantis's mission.

In addition, one of the battery control computers in Zvezda malfunctioned after launch in July. It was replaced earlier today.

To save weight, Zvezda was launched with just five of its eight batteries installed. When the station is unmanned, it can operate with as few as three. When a crew is on board, it needs six to be fully functional.

"If you get down to five, you'd have do start doing some powerdowns and managing which systems would be on and when," Ferring said. "Anything below five, I think, would be tough to accommodate. So as you can see, we have a fair amount of margin there."