> []# Futuretron EV Course_CHAPTER7

# CHAPTER 8: CHARGERS

## 8.1 Battery Charger

A battery charger or recharger is a device used for transferring energy into a secondary cell or rechargeable battery by driving electrical current into it.Electric vehicles are equipped with a finite size battery which discharges when driving a certain range. The batteries need to be charged again for traveling further. The chargers used to charge the batteries could be mounted in houses, offices, or in public places.

### AC Charging
In alternating current, the movement of electric charges periodically changes its direction. AC is the most widely used and preferred power for domestic appliances, factories, and homes, etc.

* **Slow AC charging** is the most common form of electric vehicle charging. An EVSE supplies AC current to the onboard charger of the vehicle which in turn converts the AC power to DC allowing charging of the battery.

So when you use a 15 Amp socket or a smart charger to charge your Mahindra e2o or the e2o plus electric car or an e-Scooter with Lithium-Ion battery, when you are charging it as - AC charging.

As noted above, India 's electric 2-wheelers, 3-wheelers and 4-wheeler vehicles have on-board chargers that charge at a rate of around 2.5kW to 3kW.

* **Fast AC charging**
Global electric cars such as the Nissan Leaf or the Tesla have higher power-rating chargers on board.
This makes faster charging by AC, from 7.7 kw to 22 kw.

* **AC Plug Connectors**
There are two types of AC vehicle-side connectors which are usually used for top-up charging at home , at work and at destinations.

Used by Indian e-Rickshaws, Mahindra e2o, Mahindra e2o Plus.

Type 2 connector Nissan Leaf, Renault Zoe etc

Simple 3 pin connector coupled with a 15 Amp plug used in Indian e-Scooters.

Demonstration video: https://youtu.be/TCnLmEJW1Kw
source:pluginindia.com

### DC Charging

Unlike alternating current, the flow of current indirect current does not change periodically. In a steady voltage the current flows in a single direction. DC 's main use is to supply electrical devices with power, and also to charge batteries. For examples batteries for cell phones, flashlights, and electric vehicles.

In this charging method DC current is sent directly via the DC charging port to the battery of the electric car. The faster charging rate (usually 50 kiloWatts or more outside India) will provide 100 or more km of charging range per hour. The availability of a major quick charging network would make electric cars more appealing than others, and lead to higher adoption rates. And having such a network would ensure that an electric car driver will take actual road trips — blowing one of the derogatory myths of electric vehicles. (Like to be limited to a short drive from home). For cab companies and businesses that may have a fleet of electric cars, DC Fast chargers are essential too.

**DC Charging Specifications:**

Power rating of fast chargers are
* 10kW/15kW/30kW/50kW or even higher capacity.

Voltage rating at which fast charging has to be carried out
* 48V/72V for Indian electric cars like the Mahindra e2o Plus P8, Mahindra e-Verito and upcoming Tata electric cars
* Up to 750V or even higher used by global electric cars like Nissan Leaf and others

**Level 1 DC Chargers**
Public DC Chargers at output voltage of 48V / 72V, with power outputs of 10 kW / 15 kW with maximum current of up to 200A. these will be called Level 1 DC Chargers.

**Level 2 DC Chargers**
Public DC Chargers at output voltage up to 1000V, with power outputs of 30 kW / 150 kW. These will be called Level 2 DC Chargers.

**DC Plug Connectors**
There are four or so DC Fast Charging connectors currently being used by electric car manufacturers all over the world.

CHAdeMO connector-Nissan and other Japanese companies like Mitsubishi

CCS connector-(BMW, GM, VW, and other carmakers)

Supercharger – Tesla standard connector

GB/T connector-BYD,Mahindra and Tata electric cars use this as standard.

## 8.2 Charging Infrastructure

### 1. Home Charging

The home private chargers are usually used with a single-phase 230V/15A plug that can produce up to a capacity of about 2.5KW of power. Therefore the vehicles can only be charged at this rate. The power billing is a part of home-metering.


### 2. Public Charging

EV guidelines advises billing the electrical power outside the home premises, and receiving charge. The power providers can even prefer from time to time to control the electricity these chargers use.


https://upload.wikimedia.org/wikipedia/commons/9/93/Nissan_LEAF_got_thirsty.jpg

## 8.3 Charger Working

### Charging System Power Flow


### What is EVSE? and Why does your Electric Car need it?

Electric Vehicle Supply Equipment (EVSE) is a protocol that helps to keep you and your electric vehicle safe while charging. The appropriate charging current is set based on the maximum current the charger can supply as well as the maximum current the car can receive, using two-way contact between the charger and the vehicle.

EVSE also has a safety lock-out feature which prevents current from flowing from the system until the plug is physically inserted into the vehicle. Using EVSE's, ARAI and Bharat EV specs suggest charging any EV safely compared to a simple 15 Amp 240 V socket.

Additionally, EVSE can detect hardware faults, disconnect power, and avoid damage to the battery electrical shorts or in case of a fire accident.

For example, the Mahindra e2o charges at a rate of 2 kW. And that is the limit at which charging occurs. Even though the EVSE can send in more power, the car charges at 2 kW.

Most EVSE's also come with additional features like
• Authentication
• Integrated payment gateways
• Software for Remote monitoring

### On-Board Chargers and Charging Stations

On-board Charger (OBC) is used for charging the traction battery in an electric vehicle (EV). The On-Board charger transforms the AC input from the grid into a DC input charging the battery.


credits:https://www.researchgate.net/profile/Sebastien_Jacques/publication/316304577/figure/fig1/AS:581657933893632@1515689466152/Typical-EV-on-board-battery-charger-topology-based-on-a-totem-pole-PFC-Soft-start.png

**AC-to-DC:** A rectifier is an electrical device that converts alternating current ( AC) to direct current ( DC), which flows in one direction only, which periodically reverses direction. That process is referred to as rectification.

**Working:**

The full-wave rectifier circuit consists of two power diodes connected to a single load resistance, each diode being taken in turn to supply the load with the current. The diode D1 conducts in the forward direction as shown by the arrows while the transformer 's point A is positive with respect to point C.
If point B is positive (in the negative half of the cycle) with reference to point C, diode D2 is in forward direction and the current flowing via resistor R is in the same direction for both half-cycles. Since the output voltage over the resistor R is the combined phasor sum of the two waveforms, this type of full-wave rectifier circuit is also known as a "bi-phase" circuit.


credits:https://www.electronics-tutorials.ws/wp-content/uploads/2018/05/diode-diode18.gif


Working video: https://www.youtube.com/watch?v=ACpoRVF4yx0

**DC-to-DC:** The converter is an electronic circuit converting a direct current source (DC ) from one voltage level to another. It is a type of electric power converter.

**Working:**
Power levels range from very low (small batteries) to extremely high (transmission of high voltage). In the different electric vehicle configurations, DC-DC converters convert HV to 48V, HV to 12V, and 48V to 12V.Low losses, high performance, low volume and light weight is the main design criteria for DC-DC converters.

**AC-DC WAVEFORM:**


Working video: https://www.youtube.com/watch?v=vwJYIorz_Aw

### Fast-Charging Power Electronics

Fast-charging electronics consists of three stages as follows: an input filter for decreasing input harmonics, an AC-DC rectifier and, a DC-DC converter for transferring power to the battery as shown in Figure below for DC fast-charging of an electric vehicle.  For AC charging, the AC-DC rectifier and DC-DC converter are part of the onboard charger, which also illustrates an advantage of DC charging. The space inside the vehicle constrains the size of the onboard charging unit. Considering that the onboard converter is small, the amount of power it can deliver to the battery is usually low (3–6 kW). The DC charger, on the other hand, is external to the vehicle, and therefore not limited in size or cost. Additionally, DC quick chargers can interface with 3-phase power and allow the charge level to be adjusted to match the battery state.

Figure: DC fast-charging power electronics modules

## 8.4 Types of EV Charging Stations

There are two types of charging stations, AC charging station and DC charging station.

An AC charging station as the name suggests supplies AC power from the grid to the EV and is then converted to DC using the vehicle's on-board converter. Also known as the Level 1 and Level 2 Chargers used in residential and commercial locations.
The advantage of an AC charging station is that the on-board charger will regulate the voltage and current as required for the EV, so communication to the EV is not mandatory for the charging station. The downside is its low power output which increases the charge time. A typical  AC charging device is shown in the image below. As we can see the AC from the grid is supplied directly to OBC via EVSE, the OBC then converts it to DC and charges the battery through the BMS. The Pilot wire is used to sense the type of charger connected to the EV and to set the input current needed for the OBC.

A **DC charging Station** gets AC power from the grid and converts it to DC voltage and uses it to charge the battery pack directly by by-passing the On-board Charger (OBC). These chargers usually output a high voltage of up to 600V and a current of up to 400A which allows charging of the EV in less than 30 minutes compared to 8-16 hours on the AC charger. They are often referred to as level 3 chargers and usually referred to as DC Fast Chargers (DCFC) or SuperChargers. The benefit of this type of charger is its rapid charging time while the downside is its complex engineering where it needs to communicate with EV to efficiently and safely charge it.
Below is a standard DC charging device, as you can see that the EVSE provides DC directly to the OBC bypassing battery pack.


## 8.5 Battery Charging Stratergy

### 1.Constant Voltage method

Constant current chargers vary the voltage they apply to the battery to maintain a constant current flow, switching off when the voltage reaches the level of a full charge. This design is usually used for nickel-cadmium and nickel-metal hydride cells or batteries.

**WORKING**
In a constant voltage charge, the charging voltage is maintained at the maximum voltage that should be applied to a certain type of battery while the charging current slowly decreases as the full battery charge is approached. This is an effective method when using lower voltages, as temperature usually isn't an issue, but lengthy charge times are of concern.

### 2.Constant Current method

Constant current chargers vary the voltage they apply to the battery to maintain a constant current flow, switching off when the voltage reaches the level of a full charge. This design is usually used for nickel-cadmium and nickel-metal hydride cells or batteries.

**WORKING**
As the name implies, this charging method applies a constant current as the battery voltage builds up to its full charge value. Even if the constant current applied is within the rated current, the constant current to the battery can easily cause overheating and damage, compromising the life of the battery.

Figure: Constant current, constant voltage

### 3.Constant Current-Constant Voltage method (CC-CV)

Originally referred to as "Voltage Regulated Charging," **constant current-constant voltage charging is a usual method to battery charging where the charger applies a constant current until the battery reaches a predefined voltage potential, at which point voltage is kept constant and the current continues to decrease until maximum charging is achieved.** This is shown in the figure below and is the standard method of charging batteries, but in fast-charging applications, it is limited because battery polarization becomes a problem. As expected, the CC-CV method was further modified to include multiple constant current steps, thus further improving the charge rate.


credits:https://3.bp.blogspot.com/hhS5OkEyLz0/V0dxDYYBv7I/AAAAAAAAAlE/qrBmDp6rX3E9dBWndDpUMLjSl1hGJXeTQCKgB/s1600/B.png
Figure: Constant current-constant voltage battery charging

**Trickle charging** means charging a fully charged battery at a rate equal to its self-discharge rate, thus enabling the battery to remain at its fully charged level, this state occurs almost exclusively when the battery is not loaded, as trickle charging will not keep a battery charged if current is being drawn by a load. A battery under continuous float voltage charging is said to be **float-charging**

## 8.6 Charging Time

The time required to completely charge a battery pack of a vehicle/system. The time depends on your electric car's charging point and battery power. In general, charging time for an electric car battery can vary from 10 to half hours.

### Factors That Impact Charging Time
It takes most electric vehicles overnight to fully charge. However, there are several factors that can impact the charging time of your new electric car.

* The type of charger you are using.
* How empty the battery is.
* How long you have been driving.
* The max charging rate of your vehicle and the charger you are using. It will only charge as fast as it's allowed.

### How to calculate charging time

1. First calculate your load power (P ) , by multiplying the voltage (U in volts) by the current (I, in amps). You get a value in watts.
P = U x I
For example: 16 A x 230 V = 3,680 W
2. Divide the load power by 1,000 for a value in kilowatts.
For example: 3,680 W = 3.7 kilowatts
3. Divide the power of your battery (also in kW) by the figure obtained to get the charging time.
For example: 24 kW/ 3.7 kW= 6.5 hours

### Some variables that affect an electric car’s charge speed:

* **Ambient temperature**
Colder temperatures affect a battery’s electrochemical reactions, thus charge speeds will slow as the mercury drops. Likewise, range is affected negatively by cold weather.

* **Charger type**
They type of charger (see above) determines whether you’re in for a quick pit-stop or a long lunch.
Amount of EVs connected to a station
Generally, the more EVs connected to a charging station the slower the charge rate.

* **Vehicle’s battery size**
EVs are offered with a variety of battery sizes; the capacity of an EV’s battery (measured in kilowatt-hours) determines how quickly it charges. For example, the Tesla Model S and Model X are available with a high-capacity 100 kWh battery, while the base-model Hyundai Kona’s battery is 39.2 kWh.

* **Vehicle’s battery depletion**
A fully depleted battery will charge slower than a half-full battery. To ensure a battery’s longevity, an EV’s battery management system will retard the flow to protect the battery.

* **Time of day**
Depending on where you live, power delivery could be affected by the time of day you charge your EV. Peak usage hours may slow a charger’s rate as more electricity is drawn from the grid.