What could cause an 18650 battery to suddenly stop functioning?

[jersey_emt]

One of my 18650 batteries (a dark purple Efest 2800 mAh "35A") just suddenly stopped working. It had been working fine for about 150 cycles over the past year, and I put it on the charger today and it began charging. About an hour later I went to check on it and found that the other batteries on the charger had all finished charging, but the one now read as 0.0 volts. I cleaned the terminals and the contacts on my charger and tried charging it again, and still nothing. My multimeter also reads zero volts.

The battery is already set aside to be recycled, but I'm curious as to what could have caused this. It had been working just fine and was still holding a good charge, and when I put it on the charger it read 3.5 volts and started to charge, but now it's just completely dead. There's no leaking, bulging, or anything wrong at all cosmetically.

 

[Assi]

There are several possibilities, that can explain this phenomenon. I think that in your case the battery is too old and exhausted. The Voltage shown on the charger at the beginning of the charging process is an open-circuit voltage (OCV). As soon as you start to "stress" the battery in the charger, the Voltage breaks. I don´t know which charger you use...it can be that the charger detects the battery as faulty and stop charging?! It can also be caused by the battery itself. I would even assume, that the battery was "dead" and the charger needed some time to detect that.

 

[Rickajho]

It could have been on the edge of venting. They all don't have to go up in a big BOOM! when it happens. In effect, the pressure valve may have opened and broken the electrical connection before it went to a full vent. See here:

The Anatomy of a Protected Battery

You can disregard then information about PCB circuits but IMR batteries still contain a pressure valve.

 

[Robert Cromwell]

How hard do you push your batteries?
Push them hard and 150 cycles may be about right for an Efest.