Just as EVs have different size battery packs, EV chargers charge at different speeds. Think of this in the same way you would the rate at which petrol flows from the petrol pump (EVs can’t charge as quickly as this, but the principle is the same).
A three-pin domestic plug would charge at 2.3 kiloWatts (kW), whereas an ultra-rapid public chargepoint like the kind you might find at a motorway services could deliver a charge at 150kW.
Determining how long an EV would take to charge up is therefore a simple question of dividing the battery size by the speed of the charge.
For example, a 100kWh battery would take 40 minutes to go from full to empty using a 150kWh charger. If the charger you found only delivered electricity at 50kW, it would take two hours; and if all you had was a three-pin socket it would take a little under 43.5 hours (100 divided by 2.3 = 43.48).
If the electric car in question had a smaller battery, let’s say a 50kWh pack, it would take 20 minutes to go from full to empty on a 150kW charger, 60 minutes on a 50kW charger, and 21.74 hours using a three-pin socket.