Analysis of BYD's dual-gun charging and dual BDU technology synergy design

The following article focuses on the dual BDU safety design of the distribution set, and conducts in-depth analysis from three aspects: technical principles, practical applications and synergistic value.

A. Introduction to dual-gun charging technology

1. Technical principles and implementation methods

Dual-circuit independent charging: Each charging port corresponds to a set of charging circuits, which can be charged with a single gun boost, and also supports dual-gun charging. After the dual guns are inserted, the current is merged through the high-voltage dual BDU distribution box, and the total power is doubled.

Compatibility design: Supports new and old charging national standard protocols, combined with dual boost technology (such as Tengshi N7), compatible with 500V low-voltage piles and 750V high-voltage piles, covering 95% of public DC piles. It is also compatible with level 1 EV Charger, providing home users with more charging scene options.

2. Performance and user experience

Power and efficiency: Taking the BYD N7 as an example, the power of a single gun is 150kW, the peak power of dual guns is 230kW, and it can replenish 350 kilometers in 15 minutes (CLTC working conditions), which is comparable to the efficiency of super charging piles.

Flexible replenishment strategy: advocate "dual guns with low power, single gun with high power", and support "multiple openings with one number" (single account starts dual guns) to optimize resource occupation conflicts.

3. Supporting thermal management technology

Composite direct cooling system: direct cooling plates are laid on both sides of the battery, the cooling area is increased by 100%, and the heat exchange capacity is increased by 85%, ensuring the temperature control safety when the dual guns are fast charged.

Pulse self-heating technology: in an extremely cold environment of -30℃, the battery heating rate is increased by 230%, and the full charging time is shortened by 30%, solving the bottleneck of low-temperature charging.

4. Positioning and scene adaptation

Transitional optimal solution: Under the current situation of low penetration rate of supercharging piles (current>300A piles currently account for less than 10%), BYD provides diversified energy replenishment options through "photovoltaic storage and charging integrated station" combined with existing public fast charging piles and home level 1 EV Charger.

By effectively reducing the load on the power grid and cooperating with mainstream charging pile companies, 15,000 flash charging stations (at least one pile with two guns) will be quickly built. If the dual-gun technology and megawatt flash charging technology are subsequently transferred to models within 200,000, the existing fast charging pile resources can be maximized, which can greatly reduce the time cost of user energy replenishment.

B. Coordinated control of dual BDUs, how dual BDUs control dual-channel charging and (four-wheel drive/two-wheel drive) boost charging

Early commercial vehicle dual-gun charging relied on external PDUs (power distribution units), and the space utilization rate was not considered due to the large body space (as shown in the figure below, new energy buses are directly arranged in the rear cabin).

However, passenger cars have to prioritize the space in the passenger compartment due to their small body. Traditional single-gun charging is controlled by the built-in BDU, but it is limited by the power limit of the single-gun of the national standard charging pile, and cannot achieve efficient and fast charging. Therefore, a solution that takes into account both space and charging efficiency is urgently needed.

1. System composition and connection

The battery pack includes the first BDU, the second BDU and the power battery:

First BDU: The first end is connected to the first charging port through the first charging circuit, and the second end is connected to the power battery;

Second BDU: The first end is connected to the second charging port through the second charging circuit, and the second end is connected to the power battery (or indirectly connected through the first BDU).

The dual charging circuits are controlled in parallel by the dual BDUs to achieve simultaneous charging of the dual guns. The dual BDUs are integrated in the battery pack to avoid the external PDU occupying space.

2. Internal structure of BDU

The first BDU: includes the first positive contactor and the first negative contactor, which are connected to the positive and negative poles of the first charging circuit and the positive and negative poles of the power battery respectively; there is also a first pre-charging unit (composed of the first pre-charging contactor and the pre-charging resistor in series) connected in parallel with the first positive contactor, which is used for current limiting pre-charging before charging to protect the battery.

The second BDU: The structure is similar, including the second positive and negative contactor and the second pre-charging unit, whose output end is connected to the input end of the first BDU to achieve dual-circuit parallel connection.

3. Charging circuit and space optimization

The first charging circuit: a boost circuit is set to support low-voltage DC charging or AC charging (accessed through the AC/DC integrated charging port and converted by the on-board charger). Supports AC slow charging methods such as level 1 EV Charger to meet the needs of different scenarios.

The second charging circuit: a DC charging circuit, directly connected to a high-voltage DC charging pile.

Space layout: Using the reserved copper bar in the battery pack of the four-wheel drive vehicle, the first BDU is arranged in the high-voltage connector space of the front motor, and the second BDU is arranged in the high-voltage connector space of the rear motor. Through the copper bar electrical connection, component reuse and space utilization are maximized.

Two-wheel drive vehicles can use the same battery pack. Only the high-voltage connector of the rear motor needs to be cancelled, and the dual BDU is retained to achieve dual-gun charging.

4. Advantages of dual BDU design

Charging efficiency is improved: the charging power of the dual guns is superimposed to reduce the charging time; the boost circuit is adapted to charging piles of different voltages and has strong compatibility.

Space utilization optimization: the dual BDU is integrated in the battery pack, no external PDU is required, and the reserved space of the four-wheel drive is used to meet the space requirements of the passenger compartment.

Platform design: compatible with four-wheel drive and two-wheel drive vehicles, the battery pack is universal, and the cost is reduced.

C. Summary

BYD has opened up a third technical path other than "high voltage + high current" through the collaborative innovation of dual-gun charging and dual BDU, breaking the industry's dependence on a single technical route.

Its megawatt flash charging technology not only promotes the upgrading of the industrial chain of battery materials, liquid cooling gun lines, silicon carbide devices, etc., but also promotes the standardization of industry technology through the opening of flash charging technology standards.

In addition, this kind of technical collaboration has also driven the exploration of emerging fields such as integrated photovoltaic storage and charging, promoted the evolution of the new energy vehicle energy replenishment ecosystem towards intelligence and low carbonization, and truly achieved "full-scenario adaptation" by supporting different charging methods such as level 1 EV Charger to meet the diverse needs of users.