Actually, I really wonder that what is the cycle mean? How to count the cycle? What is the real meaning of cycle life in the curve offered generally by manufacture. enter image description here

  • \$\begingroup\$ Many researchers argue that the cycle means full discharge/charge cycle, but as we know, it is not always true. In the real case, so many situation that battery discharge to 50% then recharge, so how to count the cycle in this kind of situation. \$\endgroup\$ – Hongchao Gao May 23 '17 at 4:57

Usually, a "cycle" corresponds to 100% of the nominal capacity of the battery consumed and re-charged.

For instance, with only 10% DOD, one "cycle" would comprise 10 discharge-charge cycles of 10% each. For 50% DOD, you have two cycles of discharge and recharge which together count as one "cycle" in the specifications.

If that wasn't the case, in your example diagram, 10% DOD would only yield the energy-equivalent of 700 full cycles, compared to 500 full cycles at 100% DOD.

  • \$\begingroup\$ The energy-equivalent in your words indicates that 10% DOD would yield 7000*full capacity energy or 7000*10%(DOD)*full capacity? \$\endgroup\$ – Hongchao Gao May 25 '17 at 0:10
  • \$\begingroup\$ I read it as 7000*full capacity, and 500*full capacity at 100% DOD. \$\endgroup\$ – JimmyB May 26 '17 at 9:41
  • \$\begingroup\$ Hmm. While failing to find the source I thought I had for my statement I have found some sources which seem to claim just the opposite. \$\endgroup\$ – JimmyB May 26 '17 at 11:02
  • \$\begingroup\$ In contrast, Apple explicitly states that one cycle equals 100% of the rated capacity, or 2x50%, ... See apple.com/batteries/why-lithium-ion \$\endgroup\$ – JimmyB May 26 '17 at 11:10

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