Capacity used is the numerator; nameplate capacity is the denominator. This guide shows how to calculate battery DoD % from capacity used—watt-hours consumed versus total pack Wh for an accurate discharge percentage.
Benefits
- DoD % = (capacity used ÷ total capacity) × 100 in Wh.
- Same ratio in Ah when voltage is constant across the cycle.
- Turns load logs and shunt readings into warranty-friendly DoD %.
How it works
- Sum energy used in Wh (battery monitor, inverter tally, or W × h).
- Enter total bank Wh at full charge (Ah × V or datasheet kWh).
- Multiply the ratio by 100—read DoD % for the cycle or day.
FAQ
How do I calculate battery DoD % from capacity used?
DoD % = (used ÷ total) × 100. Example: 840 Wh used from a 2,400 Wh bank → (840 ÷ 2,400) × 100 = 35% DoD. If you track Ah at steady voltage: used Ah ÷ total Ah gives the same percentage.
Can I use Ah instead of Wh for capacity used?
Yes when bus voltage is nearly constant during the discharge—used Ah ÷ total Ah equals DoD %. If voltage sags significantly, prefer Wh from a monitor or Ah × average V for better accuracy.
What if capacity used exceeds nameplate total?
Used cannot exceed total in the calculator—check whether total Wh was derated for age or whether the shunt includes inverter return energy. Regen or charging during the window reduces net used Wh.
Technical specifications
- DoD % = (capacity_used_Wh ÷ total_Wh) × 100.
- Ah method: used_Ah ÷ total_Ah (constant V).
- Remaining SoC % ≈ 100 − DoD %.
- Related: battery-depth-of-discharge-calculator, battery-energy.
Capacity used is the cycle story
State-of-charge displays summarize the present; capacity used explains the past. Calculate battery DoD % from capacity used by dividing energy withdrawn by nameplate energy. A van that pulls 1.8 kWh overnight from a 6 kWh bank hits 30% DoD—comfortable for LiFePO4, aggressive for a single flooded 12 V pair if repeated daily.
Wh accounting beats guesswork from voltage
Resting voltage maps poorly to SoC under load. Shunt-based Wh tallies or inverter cumulative draw give used capacity you can trust in the numerator. Align total Wh with the same full-charge reference the manufacturer uses—otherwise DoD % reads artificially high or low.
Log DoD % to protect cycle life
Track weekly average DoD from capacity used, not peak voltage alarms. When averages climb above chemistry guidance, add parallel capacity or shed load before capacity fade accelerates. Chain to Battery Runtime for expected Wh draw and Battery DoD to Energy Yield when planning usable kWh from nominal packs.