Simple clarification about EV charging

Question

After reading some docs about Electric Vehicles (EV), I learned that there are 4 differents charging modes.

For example, let's consider a slow recharge, where EV is connected to a single-phase domestic wall socket: its battery will absorb 16 A, so (considering a voltage of 230 V) about 3.7 kW.

3.7 kW is, often (depending on the type of contract with the grid operator), a value near the maximum power rating of an household.

So, I guess that 16 A is only the maximum current value allowed by that precise "charging mode", and that it's also possible to recharge the EV with a smaller value of current (so a smaller power). Otherwise, during EV charging, no other electric equipment (such as TVs, applicances, ...) could be supplied, without generating an electric overload.

Am I guessing right?

If it's possible to recharge an EV with a smaller power than 3.7 kW (in my case), how, and by which device, is this power value determined? Will this value be the maximum power value which doesn't cause an electric overload?

Is there anyone who could clear this?

Answer 1

On a 230 V system 16 A would be the circuit breaker rating for one circuit with a couple of sockets on it. A typical cooker would be 35 A. In Ireland the traditional connection is single-phase 63 A.

A quick web check says that the Nissan Leaf has a 40 kWh battery. Charging at your < 4 kW rating would mean an 11 hour charge, allowing for some losses.

I don't have an EV so I can't help you much further.

Answer 2

The listing in the provided link is a summary of generally accepted sources of power for EV charging systems. Your question appears to be what is allowed by those sources, which really is not related to EV charging.

Modes 1 and 2 indicate the use of a domestic socket. The power allowed is limited by the wiring, circuit breakers and for Mode 2, additional protective devices in the circuit.

Mode 3 is slightly ambiguous, although it does specify a dedicated circuit.

Mode 4 is over-simplified, in my opinion, as it appears to refer to a DC charging system, but the accompanying diagram shows an AC source and a DC load. In the real world, the AC source also includes the DC conversion integrated with the EVSE (electric vehicle service equipment).

The charging electronics for today's EVs are on-board and are relatively flexible when it comes to managing the source. An EV charger will typically accept/request the maximum current available from a given source.

In the case of Mode 1 and 2, you'll get as much current as the EVSE connected to the outlet will allow. It is the EVSE that determines the current/power.

The same applies to Mode 3 and 4, although the figures are much higher for available current.

I have a US Level 2 EVSE which is rated at 10 kW and connects to a dedicated circuit with a 50 ampere circuit breaker. The unit draws 40 amperes and fits the required 80% load rating for the breaker. I can charge at 30 miles per hour.

Generally, the public EVSE units are also managed with dedicated circuits, but typically provide only 3 kW power. This calculates to about 10 miles per hour.

Additionally, most EVs will come with a US Level 1 EVSE, which plugs into a standard 110v outlet. This results in a 3-4 mile per hour charge rate. I can't pin it down, as I've never had to suffer such a level. It's in storage bay for emergency use only, in my opinion.