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Chopperp Guru Joined: 03/01/2018 Location: AustraliaPosts: 1057
Posted: 11:50pm 11 Oct 2018
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I'm just simply amazed by some the "Big Power" stuff you guys do on this forum.ChopperP
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 01:18am 12 Oct 2018
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I suppose a psychiatrist would have a long fancy name for it, but its a really fun way to go completely crazy.Cheers, Tony.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 09:34am 12 Oct 2018
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In case you do not know, the purpose of that "hump" in the middle of the cell is it contains a spring loaded relief valve. The little decal on top pops up a little when the innards get too hot and create pressure. Under the decal is a screw plug which tensions the spring under it. The valve is just a rubber disk. I had watched an interesting Utube net necture about these cells to see if anything poisonous is inside before I opened my busted cell. Interesting also was they work more like the super capacitors (the electrolyte is similar) and not at all by some kind of chemical reaction as other battery types do.
The big cells use M12 SS bolts which can take heaps of torque. The negative terminal has a copper female thread, inside the 'plates' are made of very thin, graphite coated, copper foil which are bolted to a copper busbar/ bolt receptacle casting. The positive plates are made of thicker aluminium, coated with some lithium stuff and are bolted to an aluminium busbar/ bolt receptacle casting. Klaus
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 06:51pm 12 Oct 2018
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I often wondered if those cells were completely sealed.
Venting anything is really bad news, once its vented its GONE, and losing a little bit of something repeatedly isn't likely to add to the life of the cells. Cheers, Tony.
yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166
Posted: 10:15pm 12 Oct 2018
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if you overcharge a loose cell till it damages it will likely burst rather than vent, I think it is a safety feature to stop clamped cells exploding under extreme pressures. I'm confused, no wait... maybe I'm not...
Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406
Posted: 02:39am 14 Oct 2018
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Very likely, although they have been known to inflate into the shape of a football if not rigidly clamped to prevent swelling. That pressure relief valve in the hump must be set pretty high.
Lots of different ways to kill Lithium cells. The obvious ways are gross under or over voltage, and of course sustained very high current producing overheating.
Different people tell you different things, but one thing is for sure. Some very reliable layered protection is required to guard against some kind of overload or runaway condition if something else goes horribly wrong.
The alternative layers of protection should all work quite independently and use no common parts.Cheers, Tony.
Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904
Posted: 04:43am 14 Oct 2018
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Just in case anybody likes to see that cell valve, here is a picture:
The plug on the right can be screwed in to tension the spring located beneath it. The valve disk (under the spring) is an alu disk with a rubber layer on the sealing surface.Klaus
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