What factors can affect electric vehicle charging?

26 August 2020

Onboard charger of an electric vehicle

An electric vehicle battery is charged with DC.
However, even though it is possible to charge the battery from the alternating current (AC) power grid, the electric vehicle’s onboard charger is used to convert AC to DC.
The capacity of this onboard charger and the electricity connection capacity will determine how quickly it will be possible to charge the electric vehicle’s battery.
When charging the electric vehicle battery with direct current (DC) “directly”, the electric vehicle’s onboard charger is no longer used.
Instead, the charging station already had a current converter that transforms alternating current into direct current.
In general, electric vehicle batteries can be charged several times more quickly at the direct current (DC) charging station, as alternating current charging is limited by the power of the onboard charger.

Fast charging will be affected by the capacity of the onboard charger of the electric vehicle.
Known models such as Nissan Leaf, Hyundai Ioniq, VW e-Golf have a 6-7 kW onboard charger.
If the electric vehicle is connected to a fast charging station of 11 kW or 22 kW, the charging speed will be equivalent to 3,7 – 7,4 kW unit.

Different electric vehicle models have different technical solutions for the charging process, which is designed to ensure uniform charging of each battery element, as well as to protect the batteries from overheating, both while charging and while driving when the battery returns energy to the electric engine.
Increased battery temperature reduces the charging speed and also the distance that can be travelled.
When purchasing an electric vehicle, it is important to draw attention to the design of the battery cooling system the model is equipped with.
Battery cooling design may be passive or active.
In the case of passive cooling, battery elements are cooled by an air flow, the design is cheaper and less efficient.
Active cooling occurs using a fluid circulation system; such systems provide a more uniform battery temperature and are more efficient, but their design is more expensive and affects the price of the electric vehicle.

If an electric vehicle equipped with a passive battery cooling system has been driving actively, long-term on the motorway or at high outdoor air temperatures, the charging process may be slower than in identical conditions with the active cooling system.
In some cases, if the battery temperature is too high, the electric vehicle system may prevent charging from starting immediately after connecting to the charging station.
Of course, the charging process will start, but this will happen some time later and will take longer.