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kWh
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kW
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Zero leaves this cap inactive.
kW
Zero leaves this cap inactive.
kW
Use zero for a new or unknown pack.
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Choose Custom to enter a manual derate.
Applies only to the Custom condition.
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Use zero for an unshared charging path.
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Zero adds no queue or setup delay.
min
Zero adds no setup conditioning energy.
kW
Use recent vehicle consumption when available.
Zero suppresses the cost estimate.
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Use 3 to 6 letters, such as USD or EUR.
Enter both start and departure, or leave both blank.
Enter both times to compare against a parking window.
Keep above current SOC; values at or above the main target save no time.
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Likely bottleneck

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Quick-stop comparison

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Departure fit

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Planning boundary

This is a two-stage planning estimate, not a vehicle-specific charging curve. Pack temperature, station sharing, software limits, and upper-SOC taper can change during a real session.

Correct the charging inputs to render the power bottleneck chart.
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Battery Charge Time Calculator Estimate battery charge time across a chosen state-of-charge window using charger limits, efficiency and taper plus realistic derating and overhead.

Electric-vehicle charging time depends on the energy added to the battery and the rate at which the battery can accept it. A 75 kWh pack moving from 20% to 80% needs about 45 kWh at the battery when degradation is zero, but dividing 45 by the charger's nameplate power is only a first approximation.

The charging path is limited by its weakest power cap. The station may advertise more power than the vehicle accepts, the site may share capacity among several plugs, and battery temperature can reduce the usable rate. Conversion losses mean energy drawn from the grid is higher than energy stored in the pack.

  • AC Level 1 and Level 2 usually suit longer parking windows. Their lower power can make charging rate nearly steady across a moderate state-of-charge window.
  • DC fast charging can add energy rapidly at lower state of charge, but many vehicles reduce power as the battery fills. A high target can therefore take disproportionately longer.
  • Departure planning includes queue or setup time as well as active charging. A session can miss a departure even when the energy-only calculation appears to fit.

State of charge (SOC) is an estimate, not a laboratory measurement of available energy. Pack temperature, battery management, charger behavior, cabin conditioning, and the vehicle's own estimates can move real sessions away from a planning result. Recent charging data from the same vehicle and location is usually the best input.

Added driving range is also an estimate. It converts stored energy using the entered efficiency, so speed, weather, terrain, tyres, payload, and heating or cooling can change the distance actually gained. Charging time and range should be read as planning quantities rather than guarantees.

How to Use This Tool:

Model the battery window first, then refine the power path only as far as your vehicle and charging site data support.

  1. Enter Battery capacity, Current state of charge, and a higher Target state of charge. Use degradation only when you have a reasonable estimate of remaining pack capacity.
  2. Choose a Charging preset or set charger power, efficiency, taper start, and taper power manually. Add vehicle and site caps when either is lower than the charger rating.
  3. Select the closest Battery condition and enter any power-sharing reduction. Custom battery condition uses the manual climate derate; the other profiles use their fixed percentages.
  4. Add queue/setup time, conditioning load, driving efficiency, and electricity price only when those outputs matter. Enter both session start and departure time to check the available window, or leave both blank.
  5. Compare Total session time, Window margin, and the limiting-factor message. A shorter SOC target can reveal how much time the tapered upper portion adds.

Interpreting Results:

Battery energy added is energy stored in the usable pack window. Grid energy includes charging losses and any conditioning energy during setup, so cost should be based on grid energy rather than battery energy.

  • On time means available hours minus total session hours is zero or positive. Misses departure means the margin is negative.
  • A taper label means the upper-SOC stage is materially long relative to the lower stage. It does not claim that every vehicle follows the same two-level curve.
  • Added range inherits every uncertainty in the driving-efficiency input. Compare it with recent trip consumption before relying on it for a tight journey.

Technical Details:

The model uses two constant-power charging stages separated by a taper threshold. Before that threshold, battery power comes from the weakest charger, vehicle, or site cap after temperature and sharing derates and conversion efficiency. Above it, battery power is multiplied by the selected taper percentage.

Formula Core:

Energy, effective power, and time are calculated separately so losses and idle time are not hidden inside one efficiency guess.

Ce=C(1-d) Pb=min(Pcharger,Pvehicle,Psite)(1-c)(1-s)η E1=Cemax(0,min(Starget,Staper)-Sstart)100 E2=Cemax(0,Starget-max(Sstart,Staper))100 Tactive=E1Pb+E2Pbq

C is rated battery capacity, d is degradation ratio, Ce is effective capacity, c is climate derate, s is sharing derate, η is charging efficiency, and q is taper power ratio. A zero vehicle or site cap is inactive rather than a zero-power limit.

Active grid energy is battery energy divided by efficiency. Idle grid energy is setup hours multiplied by conditioning power. Total session time adds setup hours to active charging time, session cost multiplies total grid energy by the entered price, and departure margin is available time minus total session time.

Lookup and Rule Core:

PresetPowerEfficiencyTaper startsTaper power
Level 11.4 kW83%100%100%
Level 27.2 kW92%92%70%
DC 5050 kW90%78%48%
DC 150150 kW88%70%35%
DC 250250 kW87%64%30%

Preconditioned and mild battery profiles apply no climate derate; cold uses 12%, very cold 25%, and hot 10%. Custom uses the entered percentage. Driving efficiency accepts kWh/100 mi, kWh/100 km, mi/kWh, or km/kWh and converts with exactly 1 mile = 1.609344 km.

The target SOC and quick-stop SOC must both exceed the starting SOC. Date-time pairs must both be present and departure must be later. The limiting-factor label favors taper when upper-stage time is at least 0.2 hours and at least 25% of lower-stage time; otherwise it reports temperature or sharing when derated, then the weakest active power cap.

Accuracy and Privacy Notes:

This is a deterministic two-stage planning model, not a vehicle-specific charging curve. Real battery power can change continuously with SOC, temperature, charger voltage, battery protection, and station load management.

  • Preset values are planning assumptions. Replace them with reliable vehicle and charger observations when available.
  • Battery degradation changes effective capacity in the model; it does not diagnose battery health.
  • Local date-time values are compared as wall-clock minutes without timezone or daylight-saving adjustment.
  • Inputs and calculations stay in the browser. No live charger, vehicle, tariff, or station-availability data is queried.

Worked Examples:

DC session with an upper-SOC taper

A 60 kWh effective pack charging from 10% to 90% at a 50 kW cap and 90% efficiency stores 48 kWh. With taper beginning at 70% and power falling to 50%, the first 36 kWh take 0.8 hour and the last 12 kWh take about 0.53 hour. Total active time is about 1 hour 20 minutes, while stopping at 70% saves roughly 32 minutes.

References: