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Old 11th Feb 2013, 09:15
  #761 (permalink)  
cwatters
 
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Someone on here mentioned peak loads of 700a when starting the APU
If the battery has a 75AH capacity (reported elsewhere) then the peak draw works out at about 9C (eg 700/75 = 9.3C).

I'm not sure this is the right data sheet (also reported elsewhere) because it's for a 65AH capacity but..

http://www.s399157097.onlinehome.us/...s/LVP10-65.pdf

It mentions a max discharge rate of 5C for the family. Obviously it's possible to trade off discharge rate vs time but 5C doesn't seem very high. I've seen other LI cells rated at 30C for model aircraft use.

The internal resistance for the 65AH cell is 0.3mohms. At 700A each cell would be dissipating 700 x 700 * 0.3 x10^-3 = 147W. There are 8 in the box so the battery might be dissipating >1kW for however long the APU is drawing 700A. Presumably it doesn't draw that much for long?

Is the battery ever used to start the APU in normal use or just emergency?

Last edited by cwatters; 11th Feb 2013 at 09:19.
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