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Lithium-Ion Cell and City-El Bearings

Posted: Tue May 06, 2008 8:38 pm
by anachrocomputer
A couple of photo-sets that show the kind of crazy things that we do in Bristol -- just for fun, of course! Firstly, we have some shots of Russ and Nikki fitting new wheel bearings in a City-El:

And now one that's a whole lot more hazardous, sawing open a (duff) lithium-ion cell. Kids, don't try this at home:

Posted: Tue May 13, 2008 9:03 pm
by granada203028
Interesting to inside one of these LCPs. I have a set of 7 90Ah ones - no intension of sawing them open yet though. What do the materials look like? Can you take it apart further and see the individual plates? What is the history of the cell, how long did it last and how did it fail?

Is the electrolyte like an oil?

Presumably there is no way to rejuvenate the cell with fresh electrolyte or something.

Doesn't look that complex and therefore expensive construction. Much the same as wet Nicad. One wonders where the cost is.

Posted: Tue May 13, 2008 9:30 pm
by ChrisB
Wow love the Li-ion cell butchering :twisted:

As Granada says whats it all like in there , how nasty is it is ?? and why the heck do they cost so much, doesnt look like theres 100's of quids worth of internals


Posted: Wed May 14, 2008 7:56 am
by retepsnikrep
Looks like a few layers of interleaved electrolyte/plates and seperator from the photo. 8)

Agreed doesn't look that expensive, but don't forget if we tried to build them here H&S would mean we neded facilities akin to the uranium enrichment processing facility at Sizewell B before we could start, whereas in China some little old bloke sitting on a stool in his front room with a pair of marigolds and a face mask (if he's lucky) is putting them together for us! :roll: His Mrs will be in the kitchen mixing the electrolyte in the magimix/wooden bowl as well.

Posted: Wed May 14, 2008 12:47 pm
by ChrisB
Poor bloke :cry: makes you feel a bit guilty buying them :oops:


Posted: Fri May 16, 2008 2:18 pm
by anachrocomputer
I should explain a bit more about the lithium-ion cell. The oil-like fluid that we drained out was not an electrolyte, and the "plates" that you can see are not the actual working parts of the cell. I think the oil was either an electrical insulator, a heat conductor, or a way to keep water out of the cell.

The "plates" are plastic-wrapped units with two foil electrodes coming out of them. The foils are stacked up and bolted to the sides of the cell's terminals. So, it looks like what we have is a stack of thin, sealed cells connected in parallel and surrounded by a fluid, in a white plasic box.

As for the costs, I understand that the actual plates/electrodes unside the plastic packets must be manufactured in a multi-step process. Unlike, for instance, lead plates for a Plante cell which are little more than two pieces of lead, dipped in acid. The time taken to go through all the manufacturing steps in a lithium-ion cell is one reason for its cost.

Will attempt to cut the box open lengthways and investigate further!

PS: granada203028, if you're in Bristol, do let me know if you want to see the thing in person! And smell it...

Posted: Fri May 16, 2008 2:57 pm
by MalcolmB
Very interesting. I'd guess the main reason for filling the cells with oil would be to conduct heat to the casing. If these are made up of smaller cells connected in parallel it says something about the need for balancing; either that parallel strings are self-balancing, or that they balance sufficiently well for the manufacturer not to worry about it.
Edit: Just realised how daft that sounds. Of course parallel strings are self-balancing, since they're at the same voltage. Making up large cells from parallel strings of smaller cells must mean a higher risk of quality problems though.