Charge Time Calculator

Only above 19.2 kW -- DC fast charging. That 19.2 kW figure is the U.S. DOE Alternative Fuels Data Center's published ceiling for SAE J1772 AC Level 2 charging (80 A at 240 V), so this calculator uses it as the phase-model boundary. There, this calculator models the last 20% of charge (above 80% SOC) as a constant-voltage phase that tapers to roughly half the effective power of the earlier constant-current phase, so delivering the same energy takes about twice as long. At or below 19.2 kW (AC Level 1/2, including this calculator's own 11 kW default), the onboard charger -- not the cell -- is almost always the bottleneck at any SOC, so the pronounced 80% "knee" is essentially absent: charging proceeds at full effective power the whole way, and this calculator models it that way.

The calculator reports zero Charge Time and zero Energy to Add. If your target state of charge is already met or exceeded by your current state of charge, there's nothing left to charge, so it correctly returns "no time needed" instead of a nonsensical negative duration implying you'd need to discharge the battery to reach a lower target.

Energy to Add is the energy that actually ends up stored in the battery -- Battery Capacity times the state-of-charge gap you're closing. Energy from Grid is larger: it divides Energy to Add by Charger Efficiency to show how much the wall outlet must supply once conversion losses are accounted for. The gap between the two, Charging Losses, is energy dissipated as heat in the charger and cabling, not stored energy.

Within a single charging phase, yes -- doubling effective charger power roughly halves the time to deliver the same energy in that phase. At or below 19.2 kW this calculator treats the whole session as one phase, so the halving is clean. Above 19.2 kW (DC fast charging) crossing 80% SOC, this calculator splits charging into a full-power constant-current phase and a half-power constant-voltage phase, so a charge that spans both phases doesn't scale by one single clean ratio; it's the sum of two separately-scaling phase times.