Depth of Discharge Calculator

Calculator

Compute DoD using energy inputs, or estimate remaining energy from voltage.

White theme • Responsive grid

Project name (optional)

Method

Energy method uses remaining kWh directly.

Nominal capacity

Converted internally to kWh for calculations.

Reserve setting (%)

Usable = nominal × (1 − reserve).

Usable capacity override (kWh)

Use if BMS reports usable energy directly.

Charge remaining (energy)

Used when Method = Energy-based.

Allow remaining above usable capacity

Useful for inputs including charging conditions.

Voltage method inputs (optional)

Battery chemistry

Affects accuracy note only, not the math.

Full voltage (V)

Per pack if series cells is provided.

Cutoff voltage (V)

Minimum recommended voltage.

Current voltage (V)

Must be between cutoff and full.

Series cells (optional)

If set, voltages are normalized per cell.

Optional cycle estimate

Estimate cycle life from DoD

Cycles at 80% DoD baseline

Placeholder baseline; replace with datasheet values.

Accuracy note

Voltage method is a screening estimate. Load, temperature, and curve shape can bias results. For reports, use measured kWh or BMS energy.

Example data table

Illustrative scenarios for site batteries and temporary power systems.

Scenario	Nominal (kWh)	Reserve (%)	Remaining (kWh)	Usable (kWh)	DoD (%)
Night lighting and security load	100.0	10	35.0	90.0	61.11
Concrete curing heaters, short duty cycle	60.0	15	22.0	51.0	56.86
Tool charging station, intermittent use	15.0	5	10.5	14.25	26.32

Numbers are examples only. Use measured data for acceptance.

Formula used

Depth of discharge is the portion of usable capacity that has been used.

1) Convert nominal and remaining energy to kWh

E(kWh) = Value × UnitFactor

UnitFactor: Wh=0.001, kWh=1, MWh=1000.

2) Compute usable energy after reserve

E_usable = E_nominal × (1 − r/100)

Or use the override if your system provides usable energy directly.

3) Energy discharged

E_discharged = max(0, E_usable − E_remaining)

4) Depth of discharge

DoD(%) = 100 × E_discharged / E_usable

Voltage method (approximate)

SOC ≈ (V − V_cutoff) / (V_full − V_cutoff)

E_remaining ≈ E_usable × SOC

This simplification ignores real chemistry curves.

How to use this calculator

Enter nominal capacity and select the correct unit.
Set a reserve percentage to protect battery health.
Choose the energy method and enter remaining kWh.
Use the voltage method only for quick screening.
Enable cycle estimate if you have a datasheet baseline.
Press Calculate to show results above the form.
Download CSV or PDF for logs and reports.

For construction power planning, pair DoD with load profiles, inverter efficiency, and battery temperature limits.

Depth of Discharge in Construction Power Systems

Use this guide to turn calculator outputs into reliable operational decisions.

1) What DoD means for site batteries

Depth of discharge (DoD) is the percentage of usable battery capacity that has been consumed. In temporary power and hybrid generator setups, DoD helps crews avoid over-discharge, which can trigger low-voltage shutdowns, nuisance alarms, and reduced battery service life. This calculator defines DoD against usable energy after applying a reserve.

2) Inputs that drive the result

Three values typically dominate the output: nominal capacity, reserve percentage, and remaining energy. For example, a 100 kWh pack with a 10% reserve has 90 kWh usable. If remaining energy is 35 kWh, discharged energy is 55 kWh and DoD is 61.11%. If you have a BMS-reported usable capacity, enter it as an override to reflect real-world limits and degradation.

3) Energy method versus voltage method

The energy method is preferred because it uses measured kWh remaining. The voltage method is a screening estimate that approximates state of charge (SOC) between cutoff and full voltage. Under load, temperature changes, and flat voltage curves (common in LFP), voltage-based SOC can be biased. Use voltage mainly when metered energy is not available.

4) Typical operating bands on construction sites

Many teams target mid-range DoD levels for daily cycling to balance runtime and longevity. As a practical planning band, 50–80% DoD is commonly used for routine operations, while deeper discharge may be reserved for exceptional situations. A reserve of 10–20% is often set to protect critical loads, support surge events, and reduce the risk of cutoff trips.

5) Practical actions from the DoD result

If DoD is high, schedule charging windows, reduce non-essential loads, or add parallel storage before the next shift. Track DoD alongside ambient temperature and inverter efficiency to explain deviations. For reporting, export CSV or PDF to attach calculation assumptions to commissioning and maintenance records. Consistent assumptions make trend analysis more defensible across weeks and phases of work.

FAQs

1) Is DoD the same as state of charge (SOC)?

They are complements. SOC is what remains, while DoD is what has been used. If SOC is 40% of usable energy, DoD is about 60%.

2) Why does the calculator apply a reserve?

A reserve protects battery health and avoids cutoff events. It defines the “usable” portion of nominal capacity so DoD reflects operational limits rather than nameplate ratings.

3) When should I use the usable capacity override?

Use it when your BMS, vendor, or commissioning tests provide usable energy directly. Overrides help reflect degradation, temperature limits, and control settings.

4) Can DoD exceed 100%?

Physically, usable DoD should not exceed 100%. If inputs exceed usable energy, disable “allow above usable” or check units and reserve assumptions.

5) Is the voltage method accurate for lithium batteries?

It is approximate. Voltage depends on load, temperature, and chemistry. Use it for quick screening, then confirm with metered kWh or BMS energy data for reports.

6) How do I estimate run time from DoD?

Convert remaining usable energy to hours using average load: hours ≈ remaining kWh ÷ average kW. Apply a margin for inverter losses and peak loads.

7) What DoD should I target for daily cycling?

It depends on the battery and warranty. As a planning band, many projects aim around 50–80% DoD for routine use, then adjust using datasheet guidance.