I have created this basic overview for EV newbies. It is not intended to go into great detail or nuances but merely provide a basic overview of power sources, power storage, motor power supply and regeneration method and storage.
Energy in from charging
Alternating Current (AC)
When you connect an EV to an AC charging point which can be:
13a (2 -3kw) domestic charging cable
7kw home or public charging (fast)
11 or 22kw public charging (fast)
the cars inbuilt charger takes that AC input and converts it to DC (Direct Current) to enable that energy to be stored. The inbuilt charger will restrict the accepted AC input according to the cars design. Most common is around 7kw standard but 11kw is becoming more prevalent on newer vehicles
Around 7kw can be supplied as a single phase supply using a single phase 32amp cable
11kw upwards requires a three phase supply. A 32amp three phase cable type is required for 11/22kw charging. This cable can also be used on 7kw single phase chargers replacing the need for both types of cable.
The charge delivered at the car may be less than the advertised charging point delivery i.e 7kwh charging station could be measured for example at around 6.4kwh at the car, 11kw around 10 ish due to losses and inbuilt charger constraints.
The storage of that generated energy is held within the cars high voltage batteries.
Direct Current (DC) Rapid Charging (always tethered)
When you connect to a DC rapid or ultra rapid charger that energy is passed directly to the batteries in DC form, bypassing all of the limitations of the on-board charger and required AC conversion. The rate of DC charging is controlled by the cars battery management system design
Energy Storage
The stored energy is held in batteries in DC form. The battery types can materially be different but they fundamentally do the same job. You will see that advertised as Kwh for example 64kwh battery size. Almost all batteries have an upper and lower buffer so although, for example 64kwh is the headline figure, the usable figure will be slightly lower
Electric Motor
Most common EV motor types are AC. The stored energy (DC) requires conversion to AC to drive the motor. The car has an inbuilt inverter that takes that stored DC energy and converts it to AC for that purpose.
Regeneration
A feature of electric cars is energy regeneration. This is created using the momentum of the vehicle and the electric motor. Basically the motor reverses from drive to generation and feeds that generated energy back to the batteries. In most cases the inverter can take that generated energy and convert it to DC for storage within the batteries. The method of regeneration can vary but this is one of the most common forms. Regeneration can also occur when you use the brakes as blended braking uses the motor to slow the car down when braking normally and mechanical brakes when more force is applied. This blended braking allows regeneration during normal braking. Regeneration only occurs when the high voltage batteries have spare capacity.
12v Battery
The 12v battery is still a key part of an EV. It provides the power for the control systems and ancillary devices and without it the car is effectively dead. The 12v battery is charged from the EV HV battery using a DC/DC converter which drops the HV DC voltage down to around 14.5v. This is similar to how the alternator functions in an ICE car. The 12v battery is charged whilst in a ready to drive state, being driven and during the high voltage batteries charging or Vehicle to Load sessions. Some vehicles (including MG4) also have intelligent charging which can "top up" the 12v battery during periods of inactivity if required.
Energy in from charging
Alternating Current (AC)
When you connect an EV to an AC charging point which can be:
13a (2 -3kw) domestic charging cable
7kw home or public charging (fast)
11 or 22kw public charging (fast)
the cars inbuilt charger takes that AC input and converts it to DC (Direct Current) to enable that energy to be stored. The inbuilt charger will restrict the accepted AC input according to the cars design. Most common is around 7kw standard but 11kw is becoming more prevalent on newer vehicles
Around 7kw can be supplied as a single phase supply using a single phase 32amp cable
11kw upwards requires a three phase supply. A 32amp three phase cable type is required for 11/22kw charging. This cable can also be used on 7kw single phase chargers replacing the need for both types of cable.
The charge delivered at the car may be less than the advertised charging point delivery i.e 7kwh charging station could be measured for example at around 6.4kwh at the car, 11kw around 10 ish due to losses and inbuilt charger constraints.
The storage of that generated energy is held within the cars high voltage batteries.
Direct Current (DC) Rapid Charging (always tethered)
When you connect to a DC rapid or ultra rapid charger that energy is passed directly to the batteries in DC form, bypassing all of the limitations of the on-board charger and required AC conversion. The rate of DC charging is controlled by the cars battery management system design
Energy Storage
The stored energy is held in batteries in DC form. The battery types can materially be different but they fundamentally do the same job. You will see that advertised as Kwh for example 64kwh battery size. Almost all batteries have an upper and lower buffer so although, for example 64kwh is the headline figure, the usable figure will be slightly lower
Electric Motor
Most common EV motor types are AC. The stored energy (DC) requires conversion to AC to drive the motor. The car has an inbuilt inverter that takes that stored DC energy and converts it to AC for that purpose.
Regeneration
A feature of electric cars is energy regeneration. This is created using the momentum of the vehicle and the electric motor. Basically the motor reverses from drive to generation and feeds that generated energy back to the batteries. In most cases the inverter can take that generated energy and convert it to DC for storage within the batteries. The method of regeneration can vary but this is one of the most common forms. Regeneration can also occur when you use the brakes as blended braking uses the motor to slow the car down when braking normally and mechanical brakes when more force is applied. This blended braking allows regeneration during normal braking. Regeneration only occurs when the high voltage batteries have spare capacity.
12v Battery
The 12v battery is still a key part of an EV. It provides the power for the control systems and ancillary devices and without it the car is effectively dead. The 12v battery is charged from the EV HV battery using a DC/DC converter which drops the HV DC voltage down to around 14.5v. This is similar to how the alternator functions in an ICE car. The 12v battery is charged whilst in a ready to drive state, being driven and during the high voltage batteries charging or Vehicle to Load sessions. Some vehicles (including MG4) also have intelligent charging which can "top up" the 12v battery during periods of inactivity if required.
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