The purpose of this article is to give you a clear overview of the 4 major components in a charging system of an electric vehicle (EV). And you will also learn the basics about the energy loss that occurs in the charging system.
Major components
The complete charging system consists of 4 major components. Each component will be responsible for some amount of energy loss. We will briefly describe the 4 components and their contribution to the energy loss between the energy level at the power output and the energy level in the car battery.
Power supply (<1%)
Higher power (rate of energy) generates higher heat, which means higher energy losses. Increasing cable thickness is one way to reduce this waste.
Charging cable (<1%)
Energy is lost flowing through the cable due to resistance from electrical components. Shorter cables can help reduce these losses. Importantly, the cable must be designed for a particular charging speed to minimize loss.
On-board charger (5-15%)
The on-board charger converts AC power into DC, because the battery in an EV can only store DC power. This conversion results in heat, which is lost to the environment (waste). Modern EV batteries include liquid-cooling to reduce these losses. The on-board charger is most efficient at higher currents.
Battery (<1%)
Delivered electrical energy is converted into chemical energy in the battery. This conversion produces heat waste. Modern EVs come with thermal management systems to reduce energy loss when the battery is changing temperatures.
In general we know that energy loss is happening in each component of the charging system. And most of the charging loss (5-15%) happens in the on-board charger in the car itself, where AC power is converted into DC power. You can read more details about this study in the article from ADAC.
And that is it?
No, the entire charging process, together with the hardware components and their losses, have several external factors that influence the energy loss case by case...
One of these factors is the ambient temperature in which you charge your vehicle. If you are charging your vehicle on a winter day when it’s freezing, you will notice that the process is slower than usual. The EV battery needs to warm up before it starts charging. The process requires some energy that would otherwise go directly into the battery. On the other hand, boiling summer days are not ideal for EV charging either. Luckily, most electric vehicles have a cooling circuit to reduce the temperature of the battery when charging in hot weather. These are not exactly power losses but rather way of additional power consumption. According to some experiments, the ideal temperature for EV charging and operating is 20-25°C.
Dear EV enthusiast, please keep one thing clearly in mind: even though this charging loss story sounds pretty horrifying, it’s nothing compared to the losses when burning petrol in an internal combustion engine to drive a car!