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The vehicle charger is a vehicle electrical device that converts alternating current (AC) from household socket into direct current (DC) to charge the EV battery pack. In recent years, vehicle chargers have become V2H compatible, which can be used as a power source in disaster situations or in cases where additional power is needed, and there are also modular types available. integrated with junction box.
The vehicle charger must operate normally even in the event of low voltage conditions, voltage distortions, temporary breakdowns, temporary low voltages or voltage fluctuations on the AC side, as well as providing power Stable power to the DC side and withstands voltage and current changes of other electrical components on the vehicle.
There are two basic types of charging, you can use direct current or alternating current. If using AC power, either from an outlet or from an AC charging station, the current will pass through the charging cable to the vehicle charger, which will convert the AC current into DC current and send it to the battery. through the Battery Management System (BMS).
Vehicle charger. Author: Toyota Motor Europe (CC BY-ND 2.0 License)
If the vehicle is charged with direct current, the on-board charger is bypassed and the current is sent via the BMS directly to the battery. Therefore, the vehicle charger is not used during DC charging, but this type of charging has higher requirements for the BMS.
On top of that, the built-in charger allows you to control the current and voltage at which the battery needs to be charged (Voltage or Current Control Mode), thus ensuring the longevity of the battery.
The charger offers constant current charging mode or constant voltage charging mode, both of which are easy to operate. And each mode has its own advantages and disadvantages. In the case of constant current charging, the charging efficiency and speed are high, but there is a risk that the battery will be overcharged at a later stage and the battery life will be reduced. In the case of constant voltage charging, there is a risk that too much current will flow into the battery in the first place, which will overheat the battery and again shorten its life.
Therefore, the charger ensures that it is initially charged with a constant current, thus maintaining speed and performance, and when the voltage at both ends of the battery reaches a certain amplitude, it switches to constant voltage charging. This system is called the charging strategy and is the most important function of the onboard charger.
The first stage is called the PFC (Power Factor Controller or Power Factor Correction) stage, which converts alternating current (AC) into direct current. This part of the charger decides whether it can use one, two, or all three phases of alternating current. The 700V output voltage then goes to the second phase.
The second stage is called the LLC converter. The input is the 700V mentioned above and the output is the voltage the battery needs at a given time of charging.
Vehicle chargers can be divided according to the number of phases they can use (one, two or three) and according to their output power. The output power of a vehicle charger typically ranges from 3.7 kW to 22 kW. These two characteristics determine the price of the charger and therefore the price of the entire electric vehicle.
The standard AVID charger has an output power of 7.3 kW for single-phase use or 22 kW for three-phase use. The charger can also detect whether it can use only single phase or three phase. When connected to home AC station , will also have an output power of 22 kW, then the charging time will depend only on the capacity of the battery.
The voltage that this on-board charger can accept is 110 – 260 V AC in case of single-phase connection only (and 360 – 440 V in case of three-phase use). The output voltage going to the battery is between 450 – 850 V.
Evaluate the AC side of the KIKUSUI onboard charger PCR-WEA/WEA2 line of high-power smart AC and DC power supplies can be used to evaluate the AC side of the on-board charger. There are several AC specifications for the onboard charger: single-phase 100 V, single-phase three-wire 200 V, and three-phase 200 V, and capacities of 7 kVA, 11 kVA, and 22 kVA, but the PCR-WEA/ series WEA2 can handle all of these parameters with just a single device.
PCR-WEA/WEA2 line has extremely compact dimensions, only about one-sixth the size of conventional models, so that one unit can output up to 36 kVA and the frequency can be varied up to 5 kHz, helping recreates electricity supply conditions in many countries around the world. It is also highly resistant to surge currents, capable of delivering peak currents up to 4 times the rated value and surge currents up to 500 ms or 1.4 times the rated value.
● Various outputs: 100 V/200 V single-phase voltage, three-wire single-phase voltage, and 200 V three-phase voltage can be output with a single device.
● Ultra-compact: Up to 36 kVA output power in a single device
● High inrush current resistance: Peak current up to 4 times, inrush current up to 1.4 times (500ms)
● Sequence function: Allows supply voltage fluctuation, output start phase setting, harmonic synthesis, etc.
● Proven track record with all Japanese domestic manufacturers
● Can reproduce or simulate the electricity supply situation in many countries around the world.
Because the charging speed of electric vehicles always depends on the capacity of the weakest link, there is a tendency to use more and more powerful on-board chargers. Current research is mainly focused on reducing the size and weight of chargers, focusing on high energy density, high charging efficiency, and good heat dissipation.
Research on the first part of the charger (PFC stage) has progressed well and now achieves 98% performance. So, the overall performance mainly depends on the design and performance of the second stage DC-DC converter.
In addition, electric vehicles are also equipped with their own drive system, capable of converting electricity from AC to DC. But about its functionality and future, we will find out in the next article about the powertrain.
SEMIKI is a leading company in the market providing battery testing system solutions, programmable DC power supplies... selected Semiki products can support many requirements of famous electric vehicle factories.
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