Types of charging piles 

The types of charging piles include AC charging piles and DC charging piles. People usually refer to AC charging as 'slow charging,' while DC charging is referred to as 'fast charging' and 'super charging'.

Even though commercial electricity has been around for more than a century, the EV revolution showed the need to explain the basic principles to a new generation of users. AC Charging and its variants should be the first step in understanding how charging works. It is one of the critical points in EV ownership and the proper functioning of an electric vehicle. So, here is what you need to know about AC Charging and why it is relevant and essential to all EV owners. 

What is AC Charging?

As you may know, electric power comes in two forms – AC and DC. AC stands for "alternating current" while DC stands for "direct current." The AC is an electric current that reverses its direction and magnitude over time while DC flows in one direction. It alternates, hence the name. Due to its nature, AC is the most common form of electricity, and it is used for powering homes, lights, electrical appliances, and of course, electric vehicles. The AC can be transmitted long distances over the power grid, making this type of electricity very practical. However, for charging electric vehicles, its principles of working are a little bit different.

AC Charging for Electric Vehicles

As explained, the electric power coming from the standard grid is always in AC form, so it means that most of the chargers you will find around the city, parking lots of the shopping centers, and homes will provide your EV with this form of electricity. However, even though the power is delivered in AC form, the energy stored in your battery pack is always in DC. That means every electric car has an onboard converter that converts AC to DC to fill your battery. The converter is an essential part of any electric car since it is crucial for the charging process. This principle is used in any battery-powered device, which we can see in smartphones, consumer electronics, and electric vehicles.

However, there are also DC-only chargers for electric vehicles, also known as 'fast chargers'. They are located near industrial compounds or along the highways and use DC instead of AC. Since feeding the battery directly with the same type of electricity and bypassing the OBC (On-Board Charger), both the DC fast chargers and DC super chargers are known to fill the battery much faster than regular AC chargers.

What is DC Charging?

DC charging is one of efficient charging modes of EV charging technology that can replenish a large amount of electrical energy in a short period of time, significantly improving charge efficiency. The types of DC charging piles include AC fast charging piles and DC super charging piles. The operation principle of DC fast-charging or super-charging is to convert AC into high-voltage DC (typically 300-900V), then replenishing DC energy to battery pack of EV directly. OBC of the EV is bypassed under fast charging and super charging mode. Super charging pile is capable to extend range of EV by 200KM through 5 minutes charging.

Composition of DC Charging System

- Power conversion module

- Control Module

- Cooling system

- Input-output protection component

The 'heart' of DC Charging

- Power conversion module

In fast charging piles and supercharging piles, the functions of the power conversion module include energy conversion and power output, which are the core units of the entire system. It directly determines the maximum power, conversion efficiency, and system stability of the fast charging piles and supercharging piles. 

The power conversion module is a basic AC-DC converter. It consists of a PFC (Power Factor Correction) stage, a DC bus, and a DC-DC module.

The basic process of DC Charging

Plug DC charging gun into your EV, then kick off constant large DC charging. Constant charging elevates EV battery voltage gradually until default nominal value, while SoC (State of Charge) reach to 95% or above (different battery different SoC). 

Then a portion of the total current from the source is diverted through the shunt control, and the rest of the current trickle charges the battery. Trickle current charges the battery at its self-discharge rate by applying a constant voltage and current until battery is fully replenished.

Why choose bus bars for your DC fast charging and super charging pile application?

It has always been one of the development missions for DC charging system to increase power transforming efficiency. The overall power transforming efficiency of DC charging pile is about 95% at present in the best case, with the main losses resulting from power conversion, cables （and or bus bar）, and transformers. In high power systems, such as DC fast charging piles and DC supercharging piles, even a 1% power loss will generate a large amount of heat, which has to be dissipated by thermal management module.

stray inductance

Since high power converters are more and more widely used in DC fast charging and DC super charging, and frequent IGBT turn on/off will lead to excessively high dv/dt and di/dt. 

Under high di/dt, stray inductance in commutation circuit will induce spike voltage which generated by IGBT. The more stray inductance, the higher spike voltage. 

Excessively high spike voltage might eliminate current tail suddenly while IGBT turning off, then lead to turn-off oscillation.

Turn-off oscillation might break through then damage IGBT Field-Stop structure. In another side, oscillation will lead to turn-off loss.

After optimization, a customized laminated bus bar for DC fast charging pile, can not only meet the performance requirements but also minimize stray inductance. In the meantime, an optimized laminated bus bar should be able to suppress and minimize spike voltage.

Why choose NORTHBRIDGES bus bars for your DC fast charging and super charging pile application?

NORTHBRIDGES pioneered introducing DC Fast-Charging and Super-Charging pile industries.

Our edge-closed laminated bus bar and powder-coated bus bar have been successfully used on many key projects in series production for European customer.

LBB for DC Fast-Charging and Super-Charging pile solution

- Compact, easy installation

- Low stray inductance, superior performance

- Higher current carrying capacity

An example of Super-Charging pile, inside which our bus bar is assembled. Our Engineers used the combination of NORTHBRIDGES edge-closed LBB and powder-painted LBB solutions. It is a compact design which effectively saved space while enhanced the electrical performance.