Quote:
Originally Posted by andrewc
My RC stuff currently lives in my garage; is there a recommended temp range for storage?
I never leave mine unattended when charging or discharging, but am a little surprised to hear one has burst just sitting in storage.
Am I correct that a FIRE can only occur during charge or discharge?
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A fire is the unavoidable outcome of the pack fault allowing anode and cathode to touch each other creating a short circuit. It is more vigorous the higher the charge in the cell, but it is not something limited to it being on charge or discharge.
Above a range of 70°C to 90°C the Li-ion graphite anodes will start to self-heat. At about 130°C the separators will start to melt at which point the positive and negative electrodes will touch causing a short circuit. Now the temperature rises very quickly, the heat cannot be dissipated and the positive electrode burns releasing more oxygen that feeds the fire that results.
For fully charged cells, these temperatures can reach in excess of 600°C (1,110°F); case temperatures for lithium-iron phosphate cells are generally lower. The temperature rise is driven by reactions of the electrodes with electrolyte and release of stored energy.
Depending upon the environment around the cell, the cell vent gases may ignite. The gases are not “self-igniting.” There must be sufficient oxygen in the surrounding environment to sustain combustion of hydrocarbons and there must be a competent ignition source to ignite the vent gases. A burning cell would be a good ignition source.
The issue is that once something goes seriously wrong, the inevitable result is a thermal runaway. Cell puffing is also a cell failure, but it is non-energetic - nothing happens catastrophically.
I hope some information makes people more aware. This is not intended to scare anyone, just make people aware of the situation so they can take whatever action they need to for the risks they want to avoid. Judging by the posts above, peeps are aware and take steps to avoid risk.
HTH
