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Electric Vehicle (EV) Charging Time Calculator

Total usable capacity of your car battery.
Output of your home or public charger.
Usually 85-95% due to heat and conversion loss.

Charging Summary:

function calculateEVChargingTime() { var capacity = parseFloat(document.getElementById('batteryCapacity').value); var charger = parseFloat(document.getElementById('chargerPower').value); var start = parseFloat(document.getElementById('currentCharge').value); var end = parseFloat(document.getElementById('targetCharge').value); var eff = parseFloat(document.getElementById('efficiency').value) / 100; var resultDiv = document.getElementById('evResult'); if (isNaN(capacity) || isNaN(charger) || isNaN(start) || isNaN(end) || isNaN(eff)) { alert("Please fill in all fields with valid numbers."); return; } if (start >= end) { alert("Target charge must be higher than current charge."); return; } var energyToDeliver = (end – start) / 100 * capacity; var actualPower = charger * eff; var timeHours = energyToDeliver / actualPower; var hours = Math.floor(timeHours); var minutes = Math.round((timeHours – hours) * 60); resultDiv.style.display = "block"; document.getElementById('timeResult').innerText = "Estimated Time: " + hours + "h " + minutes + "m"; document.getElementById('energyNeeded').innerText = "Energy to be added: " + energyToDeliver.toFixed(2) + " kWh"; // Assume average efficiency of 4 miles per kWh for general range estimation var milesAdded = energyToDeliver * 4; document.getElementById('rangeAdded').innerText = "Estimated Range Added: ~" + Math.round(milesAdded) + " miles (at 4mi/kWh)"; }

How to Calculate EV Charging Time

Understanding how long it takes to charge an electric vehicle (EV) is essential for trip planning and managing your daily commute. The time it takes to charge depends on the battery's state of charge, the vehicle's onboard charger capacity, and the output of the charging station.

The Basic EV Charging Formula

To calculate the charging time manually, you can use the following formula:

Time (h) = (Battery Capacity Needed in kWh) / (Charging Power in kW × Efficiency)

Common Charging Levels

  • Level 1 (1.2kW – 1.4kW): Uses a standard 120V household outlet. Very slow, usually adding 3-5 miles of range per hour. Best for overnight charging of plug-in hybrids.
  • Level 2 (7kW – 22kW): Uses a 240V outlet (like a clothes dryer). This is the standard for home wallboxes and public "destination" chargers. A typical 7.2kW charger can fully charge a 60kWh battery in about 8-10 hours.
  • Level 3 (50kW – 350kW): Also known as DC Fast Charging. These can charge an EV from 10% to 80% in as little as 20 to 45 minutes. Note that charging speed slows down significantly after 80% to protect battery health.

Factors That Influence Charging Speed

Real-world charging times often vary from theoretical calculations due to several external factors:

  1. Onboard Charger Limit: If your car's onboard charger is limited to 7kW, plugging into a 22kW AC charger will still only charge at 7kW.
  2. Temperature: Cold weather increases internal resistance in the battery, slowing down the chemical reaction and the charging rate.
  3. State of Charge (SoC) Curve: Batteries charge faster when they are empty and slower as they get full. The "tapering" usually starts at 80%.
  4. Grid Load: If multiple EVs are charging at the same location, the available power might be shared, reducing your individual charging speed.

Practical Example

Imagine you have a Tesla Model 3 with a 75kWh battery. You arrive home with 20% charge and want to hit 80% for the next day using a 7.2kW Level 2 home charger. Assuming 90% efficiency:

  • Energy needed: 60% of 75kWh = 45kWh.
  • Effective Power: 7.2kW * 0.90 = 6.48kW.
  • Time: 45kWh / 6.48kW = 6 hours and 56 minutes.

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