Basic technical knowledge for charging EVs

How to calculate charging power, charging time and range

Three important basic concepts of e-mobility

Charging power

(single- or triple-phase)

For working out the charging power, you will need the number of phases, the voltage and amperage of your power connection for the charging station. For a triple-phase connection, the way in which the charging station is connected to the network is also important. It will depend on whether the voltage is 230 V or 400 V, arranged in a star or delta connection. If you have this information to hand, you can easily work out the values using the following formula:

Charging power (single-phase alternating current):

Charging Power (3.7 kW) = Phases (1) x Voltage (230 V) x Amperage (16 A)

Charging power (triple-phase alternating current), star connection:

Charging Power (22 kW) = Phases (3) x Voltage (230 V) x Amperage (32 A)

Alternatively: charging power (triple-phase alternating current), delta connection:

Charging Power (22 kW) = Root (3) x Voltage (400 V) x Amperage (32 A)

An example:

If you want to reach a charging power of 22 kW, your electric installation must be set up for triple-phase charging with an amperage of 32 A.

What influences the charging power?

Factors such as the temperature of the battery influence the charging power. If the temperature is too low or too high, the charging power is throttled to protect the battery. This can occur especially on cold winter days. We therefore advise charging the battery directly after driving for a long time and not the next day when the battery has cooled down again. The battery's state of charge also plays a role. The fuller it is, the slower the battery charges. Charging in the range between 20 and 80 percent SoC (State of Charge) is recommended so that high performance is achieved.

Charging time

You can work out the charging time simply by dividing the battery capacity by the charging power of your electric car. For the Tesla Model 3, this means: 75 kWh divided by 11 kW equals 7 h. However, the charging power is not constant during the charging process, but can be limited depending on the state of the battery. For this reason, we add at least half an hour in our calculations.

How is the charging time calculated?

Charging Time = Battery Capacity  / Charging Power

For example: 7 h = 75 kWh / 11 kW



How far you can get on one battery charge

For calculating the range, you simply divide the battery capacity by the energy usage and multiply the total by 100. Please bear in mind that this only concerns calculated values. The actual range depends on the mode of operation and the usage of electrical loads, such as heating, amongst other things. Moreover, the entire capacity is often unavailable, for the purposes of protecting the battery.

How is the range calculated?

Range = Battery Capacity / Energy Load  

For example: 469 km = 85 kWh / (18,1 kWh / 100 km) 

How can you increase the range?

Our 5 professional tips help you get the most out of your electric car's range.

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