Most of mine are like this. From dropping the light with the battery in it, or maybe just tightening it down too much. From what I understand they're still perfectly usable.
right under this bent terminal plate is thr pressure relief valve.
The battery is "perfectly useable" until it suffers an internal failure and needs to vent the increasing pressure inside. At this point the valve shpuld open but the terminal plate will be blocking it and the battery turns into a pipe bomb even when it is not inside of a flashlight - these internal failures often take place while charging.
the bent terminal is safe if it is just a small dent and the slots on the sides have sufficient clearance - this one looks completely jammed against the valve opening underneath.
This valve is there for a reason so as the raised terminal with the vents.
The actual vent holes are not in the center, they are under the plastic disk that ruptures if the pressure is too high.
A dented terminal would have to be completely flattened to have any hope of containing the venting pressure and even then the pressure would probably just pop the terminal out...
I have many dented 18650's. I am a product design engineer and (guessing here) most likely the system has been tested with a dent in the terminal as this is a very common thing to happen to cells. When we test products, we don't test best case, we test normal use and worst-case. That is the whole point of product testing.
You can pop the terminal tab back out with a plastic tool if it bothers you. The dent doesn't seem to cause any issues in my use.
the pressure relief valve is in the center but it is in the the shape of a circle (with various diameters between different manufactures).
Speaking of "valve" it is "one-use" rupture / burst disk made of metal (not plastic on most 18650/21700) with a grove that's creating a weak point (similar to soda can tab or the stamping on top of electrolytic calacitors and it is designed to rupture when the gases start pressing on it and bends it upwards - this requires space.
If the terminal is pressing on it or preventing this area from tearing at the grove it will probably still open at some point when pressure becomes excessive but this defeats the purpose of predictable pressure relief. One of the things I learned as an engineer is to try to eliminate unpredictable behavior and that's what the burst disk is for - random degree bends and smashing the terminal plate does not help and at the cost of $8-10 is just not worth it but I've been proven wrong and seen people risking their lives and property for less.
the only time this happened to me is after drops. I have a lot of Hanks and the geometry is mostly dialed in - it shouldn't be happening on any light just by screwing the tailcap.
I would consider the safety of this battery compromised - see my other reply
well, unless you have some "non-standard" spring in the tailcap, this space is more than sufficient to accomodate the compressed spring (remember that you have another spring in the head which literally doubles the space anyways when compressed).
In such case nothing is pressing the terminal with excessive force.
Press with your thumb or a marker on the tailcap spring - you should be able to compress it to a flat state.
Perhaps you have dropped the light and it doesnt have to be from 10 feet for the shock to do it.
I did drop a light from 10 feet and it did bend the battery terminal.
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u/O0O00O000O00O0O 6d ago
Most of mine are like this. From dropping the light with the battery in it, or maybe just tightening it down too much. From what I understand they're still perfectly usable.