Active Balancing Technology

Energy Transfer Balancing Voltage Difference 

Active balancing technology transfers energy between cells, taking from high and supplementing low, achieving fast balancing with higher efficiency!

Passive balancing relies on discharging and heating to consume high-voltage cells to buy time for low-voltage cells, and the balanced power is wasted.

Multi-scenario applications

Widely used in batteries for small sightseeing vehicles, mobility scooters, car-sharing, high-power

Energy storage, base station backup power, solar power stations, etc.

Also can be used in battery packs for balancing maintenance, repair, etc.

Application fields: Power lithium batteries, energy storage lithium batteries

Same-port Protection Board Five-Step Wiring Method

(Taking one string connection as an example, the same can be applied to other string protection boards)

1. What is same port and what is separate port?

For example, a 20-string 64V 100A protection board. Same port means that your charging negative and discharging negative are connected to the same point on the protection board (P-), the charging and discharging negatives share one interface, so its charging current and discharging current are both the same 100A. Separate port is just the opposite, the charging negative (C-) and discharging negative (P-) are separated, connected to different points on the protection board, so the charging and discharging currents are different, discharge 100A, charge 100A.

2.The relationship between battery capacity and protection board current.

The size of the battery capacity is not directly related to the current size of the board used. Large capacity does not mean large battery, it mainly depends on the continuous current, that is, the larger the current limit of your controller, the larger the continuous current of the selected protection board, and it has no direct relationship with your battery capacity.

3.What kind of charger should I choose?

Lithium batteries must be charged with a lithium battery-specific charger, never use a lead-acid battery charger. Using a lead-acid charger may cause high voltage to break down the MOS tube of the protection board, resulting in the protection board not protecting against overcharge. Iron lithium battery charger voltage = number of battery strings *3.65V; Ternary battery charger = number of battery strings *4.25V.

4.What current protection board should I choose?

The current of the protection board depends on the current limit of the controller, and the current limit of the controller depends on the power of the motor. For example, if the motor is 64V, 1000W, then the current is 1000/64=15.6A. At this time, the controller current limit must be greater than 15.6A, and the protection board's current limit must be greater than the controller's current limit. In practice, a margin must be left during selection.

Common Protection Board Faults and Troubleshooting Methods

Does not power on

1. Ensure that the last wire "B+" of the wiring harness is connected to the battery total positive;

2. Charge to activate and power on, ensure the charger voltage is more than 4V higher than the battery pack voltage to activate;

3. Check if the charger has voltage output;

Voltage inaccurate

1. Use a multimeter to measure the actual total voltage of the battery pack, and fill in the actual total voltage in the parameter setting page under "Voltage calibration";

Current inaccurate

1. The B- and P- of the protection board are both 2 7AWG wires, both need to be connected in parallel, otherwise it will cause current error;

2. Use a clamp meter to measure the actual current of the battery pack, and fill in the actual current in the parameter setting page under "Current calibration"; the larger the actual current, the higher the calibration accuracy;

Capacity inaccurate 

Step 1: First set the battery capacity, set it to the original capacity of the battery,

you can set it slightly larger, for example, if the battery capacity is 100AH, you can set it to 120AH

or 150AH.

Step 2: Discharge the battery through the instrument until the battery is completely discharged, until the protection board prompts single undervoltage protection.

Step 3: Charge the battery, do not interrupt during charging, until the protection board prompts single overvoltage protection.

After completing the above steps, the capacity will be automatically updated, and the battery capacity displayed in the APP will be the actual capacity of the battery. At this time, the SOC will also be accurate, and all capacity-related information will be accurate.

Knowledge about Battery Balancing

 Why do batteries need balancing?

The battery itself still has available capacity, but due to imbalance between batteries and the limitation of safety voltage set to protect the battery, the battery system cannot continue to perform as expected. In addition, the service life of the battery in the vehicle is shorter than the life of the vehicle itself. Even if the vehicle has not reached the scrappage age, the battery must be replaced to meet power performance requirements. However, the cost of replacing the battery is quite high, which greatly restricts the development of electric vehicles.

The main cause of battery imbalance is temperature. Generally, when the operating environment temperature of lithium-ion batteries is 10°C higher than their optimal temperature, the life of lithium-ion batteries will be reduced by half. Due to the large number of series connections in vehicle battery systems, generally between 88 and 100 series, and the capacity is generally between 20 and 60 kWh, the different positions of each string of batteries may cause temperature differences. Even within the same battery box, temperature differences can occur due to different positions and heat exposure of the batteries, and this temperature difference will have a significant negative impact on battery life, causing battery imbalance, reducing range, and shortening cycle life. It is precisely these problems that lead to the inability to fully use the capacity of the entire battery system, resulting in battery system loss, and mitigating such system loss will greatly extend the service life of the battery system.

As shown in the figure, the initial capacity of the battery system is 100%. During use, the battery will gradually decay due to various reasons (mainly temperature), which is a characteristic of lithium batteries. This part of the decay cannot be recovered by balancing. The main reason for the decrease in system capacity is system loss caused by battery capacity imbalance. System loss does not mean that all battery capacity is reduced, but that the battery system has capacity but cannot use it due to imbalance.

Generally, when the battery capacity drops to 70%~80%, the battery will be replaced to maintain range. The longer the battery capacity remains above 70%, the lower the cost of electric vehicles. Without balancing and with general passive balancing technology, the capacity of the battery system will drop below 70% in less than 3 years (with one full charge and discharge per day). Well-done passive balancing can barely maintain the battery capacity at 70%. In stark contrast, well-done active balancing can minimize system loss. This active balancing can effectively reduce system loss caused by capacity imbalance, thereby extending the service life of the battery system, delaying the battery system replacement cycle, and increasing range.

What is passive balancing?

As shown in the figure, in addition to overcharge having a serious impact on the battery, overdischarge can also cause severe damage to the battery. Similarly, the BMS has an overdischarge protection function. During discharge, when the voltage of battery No. 2 reaches the discharge protection value, the BMS protection mechanism is triggered, stopping the system discharge, directly causing the remaining capacity of batteries No. 1 and No. 3 to be unusable. After balancing is activated, it will improve system overdischarge.

The advantages of passive balancing are low cost and simple circuit design; the disadvantages are that it balances based on the lowest battery residual capacity, cannot increase the capacity of cells with low residual capacity, and 100% of the balanced power is wasted as heat.

What is active balancing?

Active balancing balances by transferring power, with high efficiency and low loss. Methods vary by manufacturer, and balancing currents range from 1 to 10A.

As shown in the figure, every 6 strings of batteries form a group, and the total power of the 6 strings is transferred to the cells with small capacity. Active balancing is based on physical conversion, integrating power switches and micro inductors, using bidirectional balancing, balancing batteries through charge transfer between similar or adjacent cells, and can balance regardless of whether the battery is in discharge, charge, or idle state, with high balancing efficiency.

As shown in the figure for the working principle of active balancing charging, battery No. 2 transfers power to batteries No. 1 and No. 3. Efficient charge transfer keeps the voltages of the three batteries balanced during charging, so all batteries can be fully charged.

As shown in the figure, active balancing can also balance the battery during discharge. Cells 1 and 3 transfer power to cell 2, and the three cells discharge while maintaining a balanced voltage, ensuring that the power of all cells can be fully utilized.

Is a Higher Balancing Current Always Better?

Many people believe that the balancing current must be large enough to balance the battery, but this is actually a misunderstanding. If the cells within a battery system maintain consistent capacity during use, or if the cells are repaired before the imbalance worsens, then there is no need to use such a large balancing current.

The balancing current for active balancing does not actually need to be very large; a balancing current of 1~1.5A is sufficient. The calculation formula is:

Required balancing current=Capacity difference between cells  ÷  Time available for balancing

The capacity difference between cells refers to the difference in capacity between adjacent or neighboring cells within a battery system. Taking a battery capacity of 100AH as an example, when there is a 3% difference in SOC, balancing with a 1.5A current can achieve balance in 2 hours. Even with a 10% difference, it only takes 6.6 hours. Therefore, a 1.5A balancing current is more than enough. The larger the balancing current, the larger the volume of surrounding electronic components will become, and the price will also increase accordingly. So, adopting a large balancing current not only increases the product size but also adds to the cost.

1. Do not modify without authorization.  

2. Avoid charging indoors and in hallways; when charging outdoors, pay attention to weather conditions to prevent the battery from getting wet.  

3. Choose a matching and suitable charger, and pay attention to the use of positive and negative terminals. Avoid overcharging and disconnect the power supply in time. 

4. Avoid storing in damp, high-temperature places, and keep away from flammable and combustible materials as much as possible.

Automated Workshop

Ensuring that every product reaching the customer's hands can be used with confidence.