I have been using 18650 Li-on battery for multiple projects. one of my new cell suddenly showed 0 V and i was not able to revive it with any charger. Finally i found an interesting video on reviving these batteries. These batteries have a internal mechanical cut off mechanism. There is a small disc below the positive terminal. In case the battery gets overheated, this Disc pops out and disconnects the battery from the positive terminal. Pressing this disc with a pointed object inserted below the Positive terminal revives the battery back to the original Voltage.

Below is the video for reference.

Hi, my Li-ion Batteries also shows 0V, I shocked because I recover from laptop Battery. First i checked it with Multimeter, shows 3.9V. I searched on Youtube. I saw this video. Then i recover my batteries. Many of them throw a cells in Garbage. This video is very helpful to recover your cells.

A word of caution here folks.

As mentioned, The battery has this mechanical cutoff feature to safeguard the battery from exploding under heat. This is there for a reason and I think we all should respect it. If you have sorted it by mistake and it has gone dead, you may revive this way but in other cases its better to discard it.

There can be 2 reasons why a battery would heat and set the cut-off mechanism active.

1. If you have salvaged it from a battery pack or say laptops, if any of the battery heats up the BMS would stop working in order to safeguard the unit. If the BMS don't, the battery would do it itself. The battery may heat up when the internal resistance of that particular battery has become high as compared to other. The battery might still be usable individually but not as a pack.

2. The battery has deteriorated and is close to end of the life cycle. In such cases the battery would not hold charge for long and high internal resistance would eat up the potential difference over time automatically.

Some safety to keep in mind if you want to use a old battery.

- Always check if the battery is heating up at the rated charge rate, if so mark it faulty and discard.
- Once charged, keep the battery at normal room temperature and observe for some time if the voltage falls(like in a day or two). If it does, you can still use it but it will not last long.
- Get a discharge circuit to measure the mah hold by the battery, if the charge hold is less then half of the rated mah. Discard.
- Also, all 18650 doesn't come with this safety feature. Be more careful in such cases.
- While making any battery pack from old batteries always check if they have the same range of internal resistance.