New BLS Battery Cells - Small amount of liquid leaking from the vent cap - normal?

[doctorcupcakes]

I've had these cells for about 2 days and I've noticed on 2 of the cells there's a tiny amount of liquid bubbling out of the vent as they're being charged. I've been very careful not to overcharge them. Is this something to be concerned about? The voltage of the cells are all in the normal range. I'm posting some pictures below. The bottom picture is of a "normal" cell. Thanks

 

[doctorcupcakes]

Also, one of the cells has a sweet, fruity smell coming from the vent. I message BLS Battery and they said some outgassing is normal for the first few cycles. Anybody have a second opinion?

 

[nwillitts]

i have no idea,but i will watch this thread.

 

[Arty3]

Watching too

 

[gnubie]

Can't say I've heard anyone else commenting that happens. The electrolyte is pretty nasty stuff (read the MSDS for a lifepo4 cell if you want to see how nasty, basically burn it and you get hydrogen fluoride, mix it with water and you get hydrofluoric acid) so it would seem unusual for it to ever be vented under normal conditions. The cells are standing upright?

 

[doctorcupcakes]

Can't say I've heard anyone else commenting that happens. The electrolyte is pretty nasty stuff (read the MSDS for a lifepo4 cell if you want to see how nasty, basically burn it and you get hydrogen fluoride, mix it with water and you get hydrofluoric acid) so it would seem unusual for it to ever be vented under normal conditions. The cells are standing upright?

Yes. I put a piece of packing tape over to see if it's still gassing, and the tape is clearly developing a small bubble under it. BLS Battery told me after 10 cycles it should be fine, but to me a LiFePO4 cell gassing like that means the vent is pierced, which raises questions about how long the cell is going to last.

 

[BiduleOhm]

To me that's not normal, the battery should be airtight.

I wonder why they does that if they're not overloaded tho

 

[doctorcupcakes]

To me that's not normal, the battery should be airtight.

I wonder why they does that if they're not overloaded tho

I'm not sure either. I haven't even charged them over 3.4v. I'm gonna run it through 10 cycles and see if it stops gassing. If not, I'll try to get a replacement cell.

 

[doctorcupcakes]

UPDATE: I cycled the battery 10-15 times and it's still leaking electrolyte. So, I contacted BLS once again and they agreed to send me a replacement cell. I have to say, the customer service was pretty impressive, which was the last thing I expected from AliExpress.

 

[nosys70]

the problem with pierced valve is not the electrolyte going out, it is more the humidity of air going in.
Lithium does not like water.

 

[Ampster]

the problem with pierced valve is not the electrolyte going out, it is more the humidity of air going in.
Lithium does not like water.

I saw a video of a teardown of this kind of cell. The pouches are sealed and contain the electrolyte. That fluid is in the container surrounding the pouches. I don't think it is electrolyte. Still not normal.

 

[gnubie]

Either way, that it's leaking at all is not good + fruity smell says cell is breached, which is doubly not good.

If it's pouch based:
Why would the cooling goop leak out? Cell pouch(es) have expanded more than expected
Why the fruity smell? One or more of the cells have been breached and potentially also an indicator that the electrolyte in the cells, the paste etc, has been able to get out of the cells too. That stuff is nasty.

 

[Ampster]

I saw a video of a teardown of this kind of cell. The pouches are sealed and contain the electrolyte. That fluid is in the container surrounding the pouches. I don't think it is electrolyte

I saw the second teardown video in which he pulls the pouches which were NOT sealed. Therefor my earlier statement may not be correct.

 

[sremick]

I message BLS Battery and they said some outgassing is normal for the first few cycles. Anybody have a second opinion?

My opinion is that that's not true and any outgassing or electrolyte leakage is a sign of some degree of internal damage/failure.

The valve is a safety mechanism to allow for controlled gradual release of pressure in the event of failure, vs. pressure that builds to the point of explosion. It's like the airbags in your car. They protect you but if they've been deployed, something bad and irreversible has happened.