6,5 hour EVA to install new batteries on ISS

[VaPaL]

Starting today at 12:05 UTC, Shane Kimbrough and Peggy Whitson, will start a 6,5 hour long EVA to change some batteries on ISS.

http://spaceflight101.com/us-eva-28-preview/

[VaPaL]

 

[Darnok]

Why those batteries are not inside?

[StrandedonEarth]

As a guess, less load on the cooling systems? Also, probably bulky. If it doesn't need to be presssurized, then save the space for something that does   

Edited January 7, 2017 by StrandedonEarth

[Nibb31]

Pressurized volume is expensive.

[Nuke]

i hope they sourced their cells from a place that doesn't sell overspeced cells.

[pincushionman]

9 hours ago, Darnok said:

Why those batteries are not inside?

So their space phone station doesn't catch fire.

I kid a little, but in all seriousness, these are man-size batteries. And for all of our advances in battery tech, they are still largely vats of chemicals that release stored energy by controlled corrosion of the metallic parts inside. There is literally nothing in there that you wouldn't rather have outside instead of inside, impinging on and potentially contaminating (or worse) your living space. 

Edited January 8, 2017 by pincushionman

[todofwar]

I wonder if there will come a time when we don't do EVAs anymore. Seems there should be a way for a drone operated from the relative safety of the inside of the iss to accomplish all those tasks.

[YNM]

19 hours ago, Nuke said:

i hope they sourced their cells from a place that doesn't sell overspeced cells.

Have no worries, these are made by the Japanese, and their electric cars don't catch fire AFAIK (and so do their phones).

Edited January 8, 2017 by YNM

[StrandedonEarth]

4 hours ago, todofwar said:

I wonder if there will come a time when we don't do EVAs anymore. Seems there should be a way for a drone operated from the relative safety of the inside of the iss to accomplish all those tasks.

Good point, I thought that was what Dextre was for. Then again, they did say the procedure was started with tele-operated robotics from the ground.

Edited January 8, 2017 by StrandedonEarth

[VaPaL]

@StrandedonEarth and @todofwar A great portion of it was done by Dextre and Canadarm2. Dextre had problems with 2 bolts, but I don't know if this alone was the reason for the EVA or just added some tasks for the Astronauts.

[AeroGav]

Out of interest, anyone know if there is a thermal management system for these cells?

Lithium ion batteries don't like being charged at temperatures lower than the freezing point of water, they can't get inside the carbon anode easily enough so tend to deposit on the outside instead as a layer of pure lithium metal, which is dangerous and causes capacity loss.

They also don't like it hot.  Temperatures much above 60 degrees centigrade can lead to thermal runaway,  but even below that, the lower the temperature the better from a life expectancy point of view.

I suppose you could just insulate them really well/cover them in something that reflects sunlight with high efficiency, and they'd equalise at the "average" temperature between dayside and nightside, whatever that is.     The lithium-ion charge and discharge process is extremely efficient so won't put significant heat in the system,  if you get the maths right on

• heat energy absorbed by the sun per day (albedo)
• heat energy radiated into space
• insulation and thermal inertia

..you can probably make a passive system that works, because environmental conditions aren't going to change much from one day to the next and it's not like a Tesla car that has to cope with supercharging at 120kw or sub 3 second 0-60 accelerations.