EV Charging Basics

Classification of EV Charging

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According to different current rating, basically there are three types of charger for EV charging.


Level 1 AC Charging

Comparatively, the charging speed is something like you walk forward, the slowest of the three. When you plug your EV into a standard wall outlet to charge, this is Level 1.

Typical power rating (1 KW)

Charge Time for 100 Miles Range (20 hrs+)

Use Case: Home, Workplace & Public Charging Stations 

Level 2 AC Charging

Comparatively, the charging speed is something like you run forward, the middle of the three. It utilizes a 208-240 volt circuit like the kind used for electric dryers.  

Typical power rating (5 KW)

Charge Time for 100 Miles Range (4 hrs)

Use Case: Home, Workplace & Public Charging Stations 

Level 3 DC Charging

Comparatively, the charging speed is something like you driving forward, the fastest of the three. It uses a much larger grid connection to DC power directly to the EV. 

Typical power rating (80 KW)

Charge Time for 100 Miles Range (40 Mins)

Use Case: On-the-go Public Charging Stations

Elements to Affect Charging Speed

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Inside an EV, there is a Battery Management System (BMS) which determines the reception of loads based on five major factors in order to protect and maximize the longevity of the battery. 


The State of Charge

How full is the battery? An empty battery charges much faster than when it is charged to 80%, starting to fall apparently to protect the battery.  

The Deterioration of the Battery

Battery deteriorates over time and lose charging capacity. A new healthy battery will charge faster.

The Temperature of the Battery

Too hot or too cold will cause the battery to charge slower. The BMS will protect the battery under extreme temperatures.

The Current & Voltage Limits of EV

Charger will match battery voltage to deliver current. At very high powers, the limitation on charging rate may become the vehicle’s battery management system rather than the charger’s capacity.

Lone or Connected Charging

For a lone charger, the max current will be poured onto it once plugged. The charging speed will be faster. For coordinated chargers, charging speed will be slower for the same current because the load is shared by chargers if there is a Load Management System in place. This is smart charging.

Internet for Chargers

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Chargers can be equipped with Internet ability for online services through the Open Charge Point Protocol (OCPP) version 1.6 or higher, which physically separates the appliance aspects of the charging infrastructure from the network backend component, the site host can easily switch charging networks without expensive equipment upgrades. 


Charging Infrastructure with Internet

Charging infrastructure can be built with a network function. By connecting to the Internet , chargers can send and receive data such as information on frequency of use to a network services provider and a site host. Online charging infrastructure allows the site host to offer radio-frequency identification (RFID), smart phone, electronic payment or membership management as well as other kinds of online customer support.

no internet

Charging Infrastructure without Internet

Non-networked charging infrastructure which is not connected to the Internet can only provide basic charging capabilities and built-in functions without advanced utilization monitoring or payment capabilities. 

Capex for Chargers

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New charging services need allot of investment. Capital expenditures (CapEx) is one of the major determinant to the selection and planning of a charging system. Before you bolt down onto a plan, you should first understand and consider the following items of cost.  

charging equipment

Equipment Cost

The cost of the charging equipment itself: hardware such as chargers, charging stations, related cables or software such as management system, operation system if any.

infrastucture cost

Electrical Infrastructure Cost

New charging services need extra electrical power. Power charging is bit for bit transmission and energy-wise in no way it can consume less to charge. Generally it requires the upgrade of the existing electrical installation for larger electrical capacity. Cost including switches, switchboards, meters or even transformer or generator and related space and civil works. This can be a large investment.

installation cost

Installation Cost

Installation cost can vary based on factors including the number and type of charging infrastructure, geographic location, site location and required trenching, existing wiring and required electrical upgrades to accommodate existing and future needs, labor costs and permitting cost.

Labor Cost

Labor cost includes the costs of the manpower for maintaining the normal operation of a charging system. Usually this labor cost is quite low because typically chargers are unattended and self-served. But chance is there you have to resolve a charging queue in dispute or a failed payment process.

Operation Cost

Operation cost includes electricity tariff, demand charges, cloud service and any network fees. Electricity tariff against different time session can be varied significantly in some regions, resulting in a much expensive electricity bill. Off-peak tariff is usually cheaper.

maintenance cost

Maintenance Cost

Maintenance cost incurs the expenditure on labor and materials for reset, repairs, updates, replacements, reinstatements or examinations of the equipment. This could also be large.


Although fast chargers are significantly more costly to build, their greater capacity means that their overall cost-to-serve (per KWH delivered) always compete with lower-capacity chargers even at lower utilizations. Refer to the “on-the-go” use case, third-party charging stations are significantly more costly than much slower charging at home or at work. It is expected that nearly all EV owners, therefore, will probably use home and work chargers whenever possible, leaving a relatively modest proportion of the market for roadside locations. In fact, the cost disparity is so large that the on-the-go use case will develop as an almost entirely distinct market. Roadside stations will likely then compete among themselves for the on-the-go market, with little consideration of the at-home market with lower charge-up prices.

What does 7.4kWh mean?

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Today, most passenger EV will take a maximum of 32A/7.4kW charging. This is indeed the fast charging standard. At 7.4kW, a Hyundai loniq (with 38.3kWh battery) can be charged from 10% to 90% in 4.5 hours, or 38km miles worth of charging in a hour. In one of our cases, the shadow power we harnessed were able to offer at least 6.7kW to turn all of the 200 parking lots into charging points. The fact tells that it is wise for you to count on this potential power for EV charging. 

In 2020, the average daily electricity consumption per Hong Kong family is only 13kWh. So 7.4kWh also means that the electrification of vehicles will push our society to build a significant amount of new electrical capacity to afford EV charging under the conventional way of power supply. It takes huge investment and imposes an insurmountable burden on our power grid that nobody will take it easy.

Obviously, we need a new way of power supply for EV charging in future. Shadow charging is the most inspiring and promising new way.