Quote:
Originally Posted by lincpimp
They spec that cell for capacity at 490mah draw. That is 1/2 an amp. So 69 of those in parallel would only give 34.5amps worth of draw to maintain the rated capacity...
99 in series gives around 360volts nominal. So 360v at 34.5amps gives 12420watts or 16hp...
Maybe my math is wrong? Or I am looking at the specs incorrectly? 16hp is enough to keep a car rolling at speed, not enough to get it moving with any authority.
Even at 4.9amps per cell discharge at around 3.3v you only get about 140hp. And that will limit the capacity about 15% (of course you do not need full hp all of the time).
I am really trying to see the benefit of these cells, but I feel something a bit more powerful would enhance performance, and would also last longer as the pack would not be as stressed...
Maybe I am looking at this all wrong...?
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The 490mA is a discharge of about 0.20C and the 4900mA is a discharge of about 2C. The capacity is there, but the cell's ability to deliver the Amps needed just isn't there. Your math is correct, but the Tesla is asking for more Amps at hard starts. In one video I saw, they had a Amp meter and it was showing over 800A. At that level, yes the car would move, but the voltage drop would be huge and this is why I think the pack needs to be cooled. High power lithium cells usually needs to be heated to above 25 degrees C (Most are tested at 25 degrees C) to perform at its best.