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

A 100 amp-hour battery is discharged at a 1C rate. What current is that?

100 amps; 1C empties the full battery in 1 hour.

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  1. 1 amp
  2. 10 amps
  3. 100 amps ✔

Why: C-rate scales current to the battery's capacity. 1C means the current that would drain the whole battery in one hour, so for 100 Ah that is 100 A. C/2 would be 50 A.

Huh, didn't know that: A 5C rate on that same battery would be 500 amps, emptying it in about 12 minutes.

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Why did the battery go to therapy? It felt totally drained.
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References

Answer: 100 amps. C-rate scales current to the battery's capacity. 1C means the current that would drain the whole battery in one hour, so for 100 Ah that is 100 A. C/2 would be 50 A.

  1. MIT Electric Vehicle Team, A Guide to Understanding Battery Specifications web.mit.edu/evt/summary_battery_specifications.pdf
    A 1C rate means that the discharge current will discharge the entire battery in 1 hour.
    Checked 2026-10-10.

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