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SESK: Stuff Everyone Should Know · sesk.info/eng-capacity-vs-c-rate

Discharge a battery at a much higher C-rate. What happens to the amp-hours you get out?

Capacity goes down as the C-rate goes up.

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  1. It stays exactly the same
  2. It decreases ✔
  3. It increases

Why: Fast discharge wastes more energy as heat in the battery's internal resistance, and voltage hits cutoff sooner. So a capacity rating names the discharge rate used.

Huh, didn't know that: Usable energy in watt-hours also drops as the C-rate rises.

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My battery is like me at a buffet. Rush it and it gives up early.
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References

Answer: It decreases. Fast discharge wastes more energy as heat in the battery's internal resistance, and voltage hits cutoff sooner. So a capacity rating names the discharge rate used.

  1. MIT Electric Vehicle Team, A Guide to Understanding Battery Specifications web.mit.edu/evt/summary_battery_specifications.pdf
    Capacity is calculated by multiplying the discharge current (in Amps) by the discharge time (in hours) and decreases with increasing C-rate.
    Checked 2026-10-10.

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