How to use this calculator
- Enter usable battery capacity.
- Set starting and target charge.
- Enter charger power and expected efficiency.
- Add a high-SOC slowdown estimate, then calculate.
#1337 · Energy & Environment Tool
Electric Bus Charging Time Calculator
Estimate how long an electric bus will occupy a charger, including usable charger power and the slower charging that can occur near a high target state of charge. Use the result to plan vehicle turns, depot windows, and route readiness.
Calculator
Fleet scenario inputsFormula
Battery energy = capacity × (target SOC − start SOC). Base time = energy ÷ (charger power × efficiency). Taper time is added only for energy above 80% SOC.
What the result means
The main result is estimated plug-in time under steady availability. Queue time, battery conditioning, charger sharing, and power limits are outside the estimate.
Actual charging curves depend on vehicle, battery temperature, charger, and state of charge.
Example calculation
A 420 kWh battery charged from 20% to 90% adds 294 kWh. At 150 kW and 92% efficiency, with a 20% slowdown above 80%, estimated time is about 131 minutes.
Tips for better results
- Use the lower of vehicle and charger power limits.
- Allow time for connection and dispatch checks.
- Avoid unnecessarily high target SOC when turnaround matters.
- Measure actual sessions to refine efficiency and taper inputs.
Frequently asked questions
Why can charging take longer than the charger rating suggests?
The charger rating is a maximum; vehicle limits, losses, temperature, and high state of charge can reduce average power.
How does charging efficiency affect the estimate?
Lower efficiency means more grid energy and a longer session for the same battery energy added.
Why is charging above 80% treated separately?
Many vehicles reduce charging power at high state of charge to protect the battery, although the exact curve varies.
Does this include charger queue time?
No. The result estimates plug-in charging time only.
Can I use this for overnight depot charging?
Yes. Enter the available charger power and planned SOC window, then compare the result with the depot dwell window.
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Inputs and units
| Input | How it is used |
|---|---|
| Vehicle and battery values | Define the energy or capacity scenario. |
| Operating assumptions | Adjust the estimate to the fleet plan. |
| Result | Planning estimate; validate against vehicle and charger data. |