The most common problem while choosing EVSE or charging cable is to find an optimal solution. Because of power supply limitations, especially in Europe (where a single phase is often restricted to 16-25A) choosing a proper charging unit may be tricky.
1. Why factory genuine charging cable has 8-12A limitation.
The charger delivered with your EV car is limited to 8-12A. This is more or less logical because car manufacturers must assume, that EV car owners may charge from a domestic wall socket, usually limited to 10A. Domestic wires to single wall sockets use 1,5 mm2 of wire diameter as standard. For such a diameter, 10A is a huge load. Overloading of the socket may cause melting it or even fire. People believe, that circuit breakers will switch off the current in such cases, but it is worth remembering, that one breaker serves more than one wall socket, so the limitation is usually higher – like 16A. In that case, charging 16A (power = 3,6kW) won’t activate breakers, but wires and socket will stay overloaded, for a long time – as car charging is not water boiling. It takes a much longer time, thus the risk of dangerous results arises.
Even 12A (like in BMW i3, i8 charging cable) is quite optimistic, as domestic sockets are in most cases limited to 10A, so 12A means 20% overloading.
2. Do you want to charge faster? The first step is to analyze your power sources.
Start your analysis from finding a total power delivery to home (for example – 11kW) and circuit breaker power limit at the input – for example, 20A, or 16A is common. This is typical for 3-phase home installations. Sometimes there are only one or two phases available. In that case, limits may be higher – like 32A.
3. Should I load a single phase fully? Or divide the load into phases?
*** 3-phase onboard charger EV cars.
This depends simply on your car. If your car is equipped with a 3-phase charger, it can be charged from single-phase or 3-phase. Connecting all 3 phases gives you an equalization of load, so 1/3 of power will be taken from each phase. Connecting the same power through single-phase will load it 3 times more.
For example – charging the 3-phase car at home with 16A delivery per phase, with 3,6 kW power:
16A single-phase will consume all available power. This phase cannot be used for any other load.
16/3 = 5,4A per phase for 3-phase – you can still use all your phases, but the maximum load per phase cannot be more than 10,6A, so around 2,4kW.
* single-phase onboard charger EV cars.
All cars with Type1 socket are single-phase. Most of the cars with Type2 socket are also single-phase. In that case, there is no possibility to load phases equally (except two known solutions: JuiceBooster Phaser and Evtun Accelev). In that case, it will be better to separate one phase and use it only for car charging.
Alternatively, you can install a power shedding capable EVSE. This may be more expensive, but such EVSE will reduce charging power or even – stop charging when another load at its phase is detected. Few producers are proposing domestic chargers with grid load monitoring and power shedding.