Monday, September 3, 2007

John Stranahan's LiPo Fire

This isnt high speed related, but since many high speed guys are using li-po's I thought I would post this about what happened to my friend John and his li-po batteries on Sept 1st 2007:

I had a battery fire today. Makes life exiting anyway. Here is what not to do. I took an older MaxAmps LiPo which had about 50 cycles on it. At this point it was down to 2950 mA-h at the last test from a high of 4050 or so. It had been out of service for only two months, but charged every couple of weeks. They have a low self discharge rate. The battery worked the motor fine on the bench. It seemed to charge fine 2c1, then 2c2 was fine, I last inspected it at about 1250mA-h. No puffiness. Nothing unusual. Put the TC5 down just long enough to find out 3.5 degrees was too much rear toe for our track. It completely disconnected the back. Got back to where the fire extinguisher was and got a notice that my battery was acting up. Shortly after ward it was on fire. I grabbed the extinguisher, half way to the table the battery (probably the second cell) shot out a big aerosolized jet of vapor which immediately ignited into to quite a spectacular fireball. They said it was loud. As I was closer to the action, this time, I did not hear it. The flame was 2 foot high shot all the way to the edge of the second table that was side by side with this one so 4 feet long and caught the bag, which I thought was out of reach, on fire so maybe 2 feet wide. A couple of squirts with the fire extinguisher and it was out. No faster action could really have been taken on our part because if I was at the battery, I would then have had to run to the fire extinguisher and back. So here are the losses.

In the car- The receiver is melted the fan on the speed control is melted, the car stand is melted. The setup board has melt damage. It was not under the car but beside it. Chassis is probably OK.
In the bag. The big Nylon bag caught fire and melted off the body of my other pan car. Melted two stopwatches and a voltmeter inside. And there is probably hidden damage. Here is a pic. I have some pics of the scene of the crime coming, I'll post one if it come out.

Would the battery sock have prevented secondary damage. Probably most. The explosion may have been bigger though, someone did unplug the chargers. I supect the sock would have jetted out a flame quite some distance from the type of fire I saw. Aerosolized vapor already at the flash point jetted out under some good pressure.

Just a report here. Typical procedure. Chunk those weak packs. It looks like that Aluminum Shock body is melted in two.


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