Re: Lifepo4 cells catch fire!
Posted: Mon Jun 25, 2012 10:14 am
I've seen Damiens video's. His cells have been tested strictly within the same voltage and temperature ranges of any LiFePo4. He follows the Jack Rickard School of battery testing and balancing.
It's said a CALB has been taken to 20C. I've seen a damage free 8C.
30C offers nobody any advantage unless they are at Santa Pod. Such rates are simply crazy!
Few speak of the Voltage at C which A123's excel at. Ideally, for safety a cell would deliver to a point then plummet. This is achieved with the cells Tesla uses. They have a PTC resistor mounted inside the end of each cell. They are set to resist at 1C (forgot the temp, I think 40~50 centigrade). Anything that makes them warm makes the cell series resistive. A zener/SCR with each cell could save them from over (dis)charging too but its all about the money work and volume.
However, large cells under load are easier to measure. Longer to heat up. Easier to balance. Disasters happen more slowly so can be caught. Fewer cells to maintain checks with and are proven to be far more consistent.
But like I said before. We have both made a similar decision. I've bought A123's that have quickly lost their lead over Sinopoly/CALB for energy density and all have a power density that I cannot really use.
It's said a CALB has been taken to 20C. I've seen a damage free 8C.
30C offers nobody any advantage unless they are at Santa Pod. Such rates are simply crazy!
Few speak of the Voltage at C which A123's excel at. Ideally, for safety a cell would deliver to a point then plummet. This is achieved with the cells Tesla uses. They have a PTC resistor mounted inside the end of each cell. They are set to resist at 1C (forgot the temp, I think 40~50 centigrade). Anything that makes them warm makes the cell series resistive. A zener/SCR with each cell could save them from over (dis)charging too but its all about the money work and volume.
However, large cells under load are easier to measure. Longer to heat up. Easier to balance. Disasters happen more slowly so can be caught. Fewer cells to maintain checks with and are proven to be far more consistent.
But like I said before. We have both made a similar decision. I've bought A123's that have quickly lost their lead over Sinopoly/CALB for energy density and all have a power density that I cannot really use.