7/8/2025
1. Why do we need terminal intelligent fast charging?
For safety and battery life considerations, fast charging will only provide the fastest charging for vehicles in the middle stage. When the power is charged to 80% or even earlier, the charging pile will gradually reduce the power. This is not because the charging pile is "lazy", but it is determined by the physical characteristics of the battery.
Taking the data of Xingxing charging pile as an example, the charging curve is as follows:
0%-50% stage: battery activity gradually increases, charging power rises rapidly, and the speed is the fastest;
50%-80% stage: to avoid battery overheating or overvoltage, BMS (battery management system) gradually reduces the current and the power decreases slowly;
Above 80% stage: enter "trickle charging", balance the battery cell voltage with a small current to protect the battery life.
In the first 20 minutes of charging, the battery is in the preheating stage, the activity continues to increase, and the charging power continues to increase. When the SOC reaches about 50%, the power begins to decrease; when the SOC reaches 80%, the speed slows down further and enters the trickle charging stage.
Take the two models with the highest charging speed in 2023 as an example:
Model A: 30%-80% charging takes 21 minutes, 80%-100% takes 19 minutes;
Model B: 30%-80% charging takes 30 minutes, 80%-100% takes 21 minutes.
This is one of the important reasons why terminal intelligent fast charging technology is needed.
In addition, with the widespread adoption of Type 2 EV Plug (European standard AC plug) in the European market, efficient and intelligent charging technology is becoming the focus of major car companies and charging equipment suppliers. Type 2 EV Plug has become the mainstream AC charging interface in the world with its strong compatibility, support for higher power and safety and reliability.
2. Analysis of lithium battery charging and discharging process
2.1 Lithium battery structure
The internal structure of lithium battery (taking cylindrical battery as an example) is sandwich-shaped, consisting of positive electrode, negative electrode and electrolyte in the middle. The process of charging and discharging is the process of lithium ions repeatedly moving between positive and negative electrodes through electrolyte.
Positive plate: high-purity aluminum-containing metal oxide;
Negative plate: layered graphite;
Separator: avoids short circuit caused by direct contact between electrodes and supports lithium ion penetration;
Electrolyte: allows lithium ions to move freely.
2.2 Classification of lithium batteries
According to different positive electrode materials, lithium batteries are mainly divided into:
Ternary lithium battery: the positive electrode material is nickel-cobalt-manganese or nickel-cobalt-aluminum;
Lithium iron phosphate battery: the positive electrode material is lithium iron phosphate.
Both batteries use layered graphite as the negative electrode material.
2.3 Charging and discharging process of lithium batteries
Charging: lithium ions start from the positive plate, pass through the separator to the graphite layer of the negative plate, and are stored;
Discharging: lithium ions return from the negative electrode to the positive electrode, and electrons form current through the external circuit to drive the motor into mechanical energy.
As an important interface for AC charging, Type 2 EV Plug supports the efficient, safe and stable transmission of this energy conversion process and has been widely used in the field of electric vehicles.
3. Key factors limiting charging speed
The transmission speed of lithium ions is the key to determining charging efficiency, which is divided into the following stages:
Stage 1: lithium ions are released from the positive electrode material;
Stage 2: lithium ions move to the diaphragm in the electrolyte;
Stage 3: lithium ions pass through the diaphragm;
Stage 4: lithium ions continue to move to the negative electrode in the electrolyte;
Stage 5: lithium ions are embedded in the negative electrode material.
The efficiency of each stage will affect the overall charging speed, which is why the current Type 2 AC charging technology continues to upgrade.
4. BYD's solution - negative pulse charging to alleviate lithium ion accumulation
BYD optimizes the charging terminal speed and battery life through negative pulse technology:
4.1 Relieve concentration polarization
Improve the lithium ion transmission efficiency by dynamically balancing the electrolyte concentration gradient.
4.2 Inhibit lithium precipitation
Promote the uniform embedding of lithium ions into the negative electrode to prevent the formation of lithium dendrites.
4.3 Accelerate solid phase diffusion
Shorten the migration path of lithium ions in the solid phase.
4.4 Reduce interfacial impedance
Optimize the kinetics of the SEI film and improve the efficiency of the charge and discharge reactions.
4.5 Collaborative optimization of thermal management
Improve low-temperature charging performance through intelligent pulse self-heating technology.
Combined with the intelligent control of the Type 2 EV Plug, BYD's negative pulse technology can fully release the potential of fast charging and ensure safety and battery health.
5. Summary
BYD's intelligent pulse fast charging technology achieves multiple advantages in the high SOC range through the "charge-stop-reverse fine-tuning" strategy:
5.1 Shorten terminal charging time
Negative pulse discharge reduces concentration polarization, shortens the charging time of SOC 80%-100% from 30 minutes to 18 minutes, and increases the charging speed by 40%.
5.2 Improve low-temperature charging performance
The temperature rise rate in a -30℃ environment is increased by 230%, the charging time is shortened by 40%, and there is no need for long-term preheating. The charging efficiency is close to the normal temperature level.
5.3 Extend battery life
Pulse charging effectively suppresses lithium dendrites, and the battery capacity retention rate is increased to 90%.
Driven by the combination of smart fast charging technology and Type 2 EV Plug technology, the future electric vehicle charging experience will be faster, safer and more efficient. NexwayEV is committed to providing users with advanced and reliable EV charging solutions to help create a new future of green travel.
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