What is SoC in electric vehicles?

SoC state of charge in EVs

SoC stands for State of Charge, which is the amount of stored energy in the battery. For example, if you have an 80% charge, you have an 80% SoC.

SoC is not the total potential capacity of the battery; it merely signifies the energy in the battery relative to its capacity. A 20% SoC means the battery is 20% charged and a 0% SoC means the vehicle is fully discharged.

We measure SoC in all batteries as a percentage. If you have an iPhone or Android phone, you can set it to display the percentage. Your electric vehicle will also display your remaining battery as a percentage and calculate your range.

Battery health, charge times and SoC

When charging your electric vehicle, your charger – whether it is a public charger or home charger – will refer to the SoC with estimated charge times.

Most EV manufacturers recommended charging an electric car to 80% SoC and recharging when it drops to around 20%.

In our article about how long EV batteries last, we revealed that a 20-80% charge demonstrates the best capacity maintenance over a battery’s lifespan. This is based on a study of 6,000 EV batteries by GEOTAB .

The reason a 20-80% charge is better for the battery versus a 5-80% or 0-100% charge is that it produces less heat and reduces the charge cycle time.

When charging in public, you will also notice charge times drop off a cliff after 80% – this is because DC rapid chargers cut the power output at 80% to a much slower rate to protect the charger from heat.

For example, Car Magazine found that the Polestar 2 needs 36 minutes to charge from 10 to 80% at 150kW, but the last 20% takes another 87 minutes.

Summing up

  • SoC stands for State of Charge
  • SoC is the amount of stored energy in the battery relative to its capacity
  • A 70% charge means you have a 70% SoC
  • To preserve battery health in the long run, charging to 80% SoC is recommended.

Happy charging!

Alfred Maxwell
Alfred drives a Tesla Model 3 Standard Range Plus but has his eye on a fully-electric pick-up truck. He'd love an electric Ford Ranger, which should be a real thing in a few years!