Approaches: How much load is available?
Load management determines how much power is available to the charging points. The approaches here can be divided into three categories:
- Without active management – It is debatable whether this form should make the list, since the charging points are not really controlled in this way. Each charging point is granted a constant maximum load. The individual charging points can charge with a given load at any time regardless of the current usage of the other charging points. To prevent overloads, the individual limit is set very low. As a result, peak loads are not actively reduced, nor is the total capacity optimally utilized.
- Static – The simple form. Here, a static value is set for the maximum load of all charging stations combined. Depending on the usage of the other charging points, the available power per point varies. This improves the utilization of the capacity. However, the utilization is not at the optimum and overloads are not ruled out.
- Dynamic – The more complex form. Here, the charging power is determined by the current base load. This has two advantages over the static variant. When the base load is low, more power is available for charging. When the base load is high, the charging power is adjusted so that there is no risk of overload and peak loads are actively reduced.
Strategies: Who charges when and how fast?
The approaches described above determine how much power is available to the charging points in total. However, they do not adjust how much power the individual charging point is entitled to. That is dependent on the charging strategies. There are various options here, which can be divided into three categories, although combinations are also possible:
- Serial – First come, first served. There is a maximum number of parallel charging processes. Once this number is reached, the next car cannot charge until a previous charging process has been completed.
- Balanced – The available power is distributed evenly among all charging points.
- Prioritized – Individual charging points enjoy priority. They always charge at full power. The remaining charging points either charge sequentially or share the remaining power.
Implementation: How are the charging points controlled?
Ultimately, the various solutions also differ in their technical implementation:
- Master-slave – One charging point (master) controls all other points (slaves). These are mostly systems by charging station manufacturers that are often only compatible with products from the same brand.
- Cloud systems – The charging points communicate with a server that centrally controls all charging points.
- Local systems – A local controller is installed. This controls all charging points on site and can also communicate with other systems in the cloud.
So what is the best solution?
It's impossible to make a blanket statement. Static load management is generally cheaper than dynamic – but does not offer a complete overload protection. The optimal charging strategy depends very much on the use case and individual mobility needs.
And when it comes to technical implementation, each variant has its advantages and disadvantages. Master-slave solutions are usually tied to one manufacturer but are seamlessly integrated into the charging stations. Cloud systems are prone to connection failures and have high latency. Local systems require additional hardware – but are robust against connection failures and control charging points in near real time.