Dealing with a puffed LiPo battery

I bought lot of stuff for my quadcopter in the past year and half, but never got the time to build anything. But with the holidays in sight, and having completed most of the projects that were keeping me from starting the assembling I decided to start having a look at all the components I have, as a reminder of all the bits and pieces.

While inspecting the Lipo batteries I noticed that one was slightly fatter than the other: this is usually a sign that something is wrong with it.

I don’t have a lot of experience with RC related stuff, so I asked for advices on the DiyDrones forum and people over there were very helpful explaining what the problem was and how to deal with it.

What was the problem?

The problem was that one of the 3 cells of battery was dead: sometimes it happens, I should have probably checked better when the battery arrived, but might have also been that leaving it unused for more than one year caused the battery to break. I also checked with the multimeter and in fact the 2 cells were 3,85V while the one that was puffed is 0,6V.

How to deal with it

So I had to dispose the battery somehow: Lipos are safe to treat as normal batteries (actually someone even says as normal garbage) when they are fully discharged, otherwise they might explode.

I found a very interesting page that explains how to fully discharge a Lipo battery. Somewhere around in other forums they suggest to drop the Lipo in salted water so that it slowly gets discharged, but apparently this is not a good idea, because due to electrolysis the pads get corroded before the battery is totally drained, so you are left with a battery that is partially charged, so dangerous to dispose.

What I ended up doing was attaching a 12V 20W halogen bulb (the one for the kitchen fan) to the single cells via the recharging socket: this way I was sure I was not risking of damaging the broken cell even more.

It took a few hours but at the end I was left with a totally drained battery, safe to dispose. And nothing exploded

This was my first problem with batteries: after that I bought a recharging fireproof bag, a portable charge equalizer/monitor, a in-flight low-battery alert and the AttoPilot Current sensor to feed the information on the current state of the battery back into the APM.

Never underestimate batteries.

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