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A battery is drained each day down to 65% of its capacity. What is its depth of discharge?

35%, the share of capacity used.

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  1. 35% ✔
  2. 65%
  3. 100%

Why: Depth of discharge is the percentage of capacity used when a battery is discharged. Draining to 65% means 35% was used. NREL notes the relationship between depth of discharge and battery life is non-linear.

Huh, didn't know that: NREL says battery longevity depends mainly on DOD, cycle count, time at each charge level, and temperature.

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A laptop and a book were racing. After the race, a reporter asked the laptop how it won. The laptop said, I was charged up.
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References

Answer: 35%. Depth of discharge is the percentage of capacity used when a battery is discharged. Draining to 65% means 35% was used. NREL notes the relationship between depth of discharge and battery life is non-linear.

  1. NREL: Best Practices for Operation and Maintenance of Photovoltaic and Energy Storage Systems docs.nlr.gov/docs/fy19osti/73822.pdf
    discharged down to 65% of capacity has a DOD of 35%
    Checked 2026-10-10.

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