|Sep 17, 2003, 05:43 PM|
A Lipo Explosion Recorded on Video
I previously posted a thread where I shot 3 lead pellets into a lipo cell and nothing happened. I also shorted a lipo cell with a jumper cable and again nothing happened.
This demonstration was performed only to show what a single lipo cell looks like IF it vents and ignites from an overcharge. No conclusions should be drawn from the information given, as other cells or packs may not perform in the same manner.
We\'ve all read stories of lipos exploding and starting fires, but few have ever seen what really happens when a lipo cell balloons, vents, explodes or causes a fire. The purpose of my test was to record a video of a lipo cell being deliberately overcharged to see exactly what does happen. In about 2 years of hearing of Li-Ion explosions and now Li-Poly fires, no one has taped one of the events. Now you will be able to see for yourself what happens.
I took my camcorder and tripod, 12 volt car battery, an 8.4 volt 1 amp charger, a DVM, jumper cables, and a single lipo cell that had one layer of heat shrink on it which was then taped to a piece of foam, out to my backyard.
I set everything up so I could view the Dvm while the charge progressed. I started the camera recording the event and attached the final connection to the positive post of the car battery. I checked the charger and the meter was indicating that 1 amp was flowing to the lipo. The lipo already had a full charge on it when the test began.
Just a side note...I had a 60 minute tape in the camera and the fire occurred at the 54 minute mark. Close! Yes, it took 54 minutes of overcharging a single 4.2 volt cell at 8.4 volts and 1 amp before it finally blew up. I won\'t disclose what cell was being used. Most, if not all, lipos are capable of having this happen.
I watched the voltage rise to 4.85 v, but then it dropped back down to 4.63 v after about 10 minutes. It stayed at that voltage for another 10 minutes then started to rise again. It rose to 4.91 volts and stayed at that voltage for about 20 minutes. I went up and touched the cell and it was quite warm, but I could hold my finger on it for several seconds and it wasn\'t melting the foam it was attached to.
After being at 4.91 volts for 20 minutes, the voltage started to rise again. Slowly at first, but then it began to rise much faster. As I recall the highest voltage peak was at 7.6 volts, and then in the next second, it immediately dropped to 0.11 volts.
I looked closely (but not too closely) at the cell, and it was starting to sink into the foam that was melting from the cell\'s heat. A few seconds later and white smoke begin pouring out of the cell at the end where the tabs are located. A few seconds of smoke and then a loud \"whoosh\" and a bright flame came shooting out.
Below are some still pictures of the fire. It started at 54 minutes and was over with at 55 minutes.
No fire extinguisher was used, although one was nearby. One thing you should notice, is that the foam itself is not burning and did not need extinguishing. It only melted from the heat. The flames are all from the lipo cell.
The video can be seen at http://dna.rchomepage.com/LipoFire.wmv
|Sep 17, 2003, 06:10 PM|
WOW !!! although that was a long time at Twice the voltage before it went up,
if people don't take charging li-po's seriously after seeing this
|Sep 17, 2003, 07:13 PM|
Thanks DNA for going to the trouble to do that for us. Much appreciated -
I'm pleasantly surprised at how much abuse it took before igniting.
|Sep 17, 2003, 07:24 PM|
Can you give us a rough idea of the mah of that pack? Don't need to give us the exact value, just wondering how much energy was in the pack to cause that amount of fire...
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