It's a limitation of the ac/dc transformer in the car. The batteries actually take dc to charge. Another way that Tesla innovated was having much bigger transfo

It's a limitation of the ac/dc transformer in the car. The batteries actually take dc to charge. Another way that Tesla innovated was having much bigger transformers in their cars. Charging capacity is in kw. batteries are hours of that (kwh). A regular us outlet has 1.44 kw charging capacity (120v * 12 amps). A high power car like a tesla has 85kwh or 100kwh of capacity, so 100kwh/1.44 = 69 hours, so it's not practical to drive 250 miles in a day and charge again; for that you need higher power chargers. A leaf is only 3.3 kwh (unless they increased it in the new models), tesla model s were 11 kwh or 22 kwh. Details The on board transformer has a limited capacity to charge the battery. If you only charge 120v you only need 1.44kw charger. But you'll never be able to charge faster. 220v 12 amps is 2.64 kw. Original tesla model s had either 11 kwh or double chargers, 22 kw. The model x split the difference with 11 or 17kw. 40 amp power is commonly available, 40 amp * 220 v = 8.8 kw, 71 amp * 220 = 15.6kw, 100 amps * 220 = 22kwh, the max that tesla has onboard. Did you know, a tesla supercharger is just a bank of regular car transformers that are combined to make the high power 140 kw charging power of top end superchargers (used to be around 90kw, they have kept increasing the top end, but the same plug). This page gives a nice breakdown of different models and shows the anemic charging limits of most non-teslas. https://www.clippercreek.com/three-things-determine-ev-charge-time/ https://www.clippercreek.com/three-things-determine-ev-charg...