Why does my car charge below the charger's maximum power?

The smallest limit applies: the car's battery, the station's converter or the site's grid connection. Most often the car sets the limit.

Explained in

EV charging fundamentals · Stop 04Why doesn't electricity flow immediately?Authorisation is approved, yet the display shows Preparing and power later falls on its own. Safety checks, the handshake and the charging curve explained.

A battery fills like a stadium: quickly while the rows are empty, more slowly once seats run out. As the battery fills, the battery management system lowers the power to protect the cells, most steeply above roughly 80%, so the last 20% take disproportionately long. That is why car manufacturers state fast-charging times from 10 to 80%.

From “Why the power falls around minute 20”, stop 04

Terms

  1. BMSBattery management system: the car's electronics that decide how much power the battery accepts at each moment.
  1. What happens in the seconds before charging starts?A safety check with insulation test and connector lock, a negotiation of voltage and current limits, and precharge. Only then does current flow.
  2. Why does charging power drop at 80%?Above roughly 80%, the battery management system lowers the power to protect the cells, so the last 20% take disproportionately long. That is why fast-charging times are usually stated from 10 to 80%.
  3. Why is charging at home slower than on the motorway?At home, the car's onboard charger converts AC to DC. At a fast charger, the station does this at much higher power, so minutes replace hours.
  4. Are most public chargers fast chargers?No. About three in five public charge points in Europe are AC chargers up to 22 kW. About one in five belongs to a site with 150 kW or more.