Leaking electrolyte

[jonescg]

So I pose a hypothetical:
Is it possible to have a cylindrical cell leak electrolyte and still be functional?
My VOC sensor idea has got me thinking - what if a cell leaks a little electrolyte and causes the sensor to shut the bike down. You let the pack cool down, but after no more electrolyte is discovered, you charge the bike up as if nothing happened. What are the likely consequences?

I suspect that the leaked electrolyte must have happened due to 1) physical trauma to the cell case, or 2) excessive pressure build up. Excessive pressure can only happen if the internals of the cell are able to heat up because of either 2a) an internal short or 2b) an external short.

I would have thought that the cell's internal resistance would increase rapidly due to the loss of mobile Li+ ions. By sharing the currents of it's neighbouring cells, it will heat up more, causing more electrolyte to leak... and eventually turning it into a heater.

Suspect a first response should just be - remove pack, start again, keep house.

 

[billvon]

So I pose a hypothetical:
Is it possible to have a cylindrical cell leak electrolyte and still be functional?

Not really.

If a cylindrical cell leaks it's experience an overpressure, and something else has gone drastically wrong (i.e. internal short, overcharge.)

If it's a pouch cell then there's a hole, and you have days to weeks before water ingress causes it to swell and rupture.

 

[Alan B]

We've had pouch cells swell but continue to work. They are still working years later, and still slightly swollen.

 

[999zip999]

You do not need a battery fire. Just the smoke alone will wreak many things. Then the water needed to put out the fire. Plus the fire itself. Do you keep your battery inside the garage ? Or in the bbq ?

 

[billvon]

We've had pouch cells swell but continue to work. They are still working years later, and still slightly swollen.

Were they leaking?

 

[Alan B]

No leaks, just minor swelling.

However a cylindrical cell in the same state doesn't have room for expansion and would probably have to leak.

 

[jonescg]

Just looking at the most useful response to detecting a leaky cell. Personally I would say remove pack, source a new one and deal with the leaky one outside. But if it was possible to use the leaked electrolyte as a warning and you can be assured of a safe limp-home it might offer some versatility.

I've seen swollen cells still function, however their IR is higher so they tend to put out less power. But once they rupture and leak, they dry out quickly and become a lit fuse...