Electronic – Storing a possibly damaged Li-Ion battery


I replaced the battery of my mobile phone earlier this day. Because of adhesive, narrow spaces etc it happened that I slightly bent the old battery during removal (see sketch below).

    top view     v---contacts                            side view
----------------[]-                                              _________ 
|                 |                              _______________/  _______| "bottom"
|                 |    contacts on this side >   |________________/
|                 |                                                       
|                 |                                             |<--1cm-->|
|                 |
|                 |

Sorry for the bad sketches, I stored the battery away to (probable) safety and didn't take any pictures beforehand. The bend starts about 1cm away from "bottom" and at the very bottom the battery is not more than 1mm elevated. There is no visible damage of the hull.

I cannot dispose the battery before friday and hearing of all the troubles regarding Li-Ion and LiPo batteries I am a bit worried now.

It is a 2300 mA Li-Ion mobile phone battery and at the time of removal it was probably around 20-25 % charged.

I have limited options for storage, no garden available. I thought about burying it in a glass jar filled with sand (would be available) in order to make it impossible for a fire to start (least possible amount of air available) – but the tightly closed lid would make it impossible for fumes to escape and the jar might explode from pressure?

I could also wrap the battery (or jar) in some fireproof blanket (like they are available for kitchen fires) and just hope for the best.

Do I have to worry at all? I know that LiPo-batteries like they are used for racing cars or model planes can be dangerous when damaged, but what about phone batteries? How should I store it in order to be safe until friday?

How fast would I notice any possible danger, if the battery would have been damaged? I watched it for about 3 hours before storing it away (it's in the jar of sand at the moment, with the lid open) and nothing happened. Does that mean that there will not happen anything anymore?

Best Answer

The battery is likely less dangerous than the low internal resistance batteries used in RC models. Nevertheless, there is still a very small chance that it will short out internally, puff up, rupture, and burn the place to the ground, even spontaneously after some time. LiPo- and Li-Ion batteries can be rendered inert (chemically unable to enter thermal runaway) by discharging all cells to 0V.

In order to safely dispose of the battery, just submerge it in salt water. The conductive water will then find its way into and short out the terminals of each cell in the pack. After a few hours each cell should reach a potential of 0V, at which point the battery is completely safe.

For a less messy approach, you can connect a power resistor of a few ohms or even a flashlight bulb across each cell, for the same effect.