Off Grid Solar System Lifepo4 Battery System

- Apr 24, 2018-

With the rapid development of wind power, photovoltaic and other renewable energy power generation industries, the issue of abandoning and rejecting wind caused by interference, pollution, and randomness of power grids has become increasingly serious. Since 2011, GSLIBATT has developed and tested the use of chemical energy storage systems based on lithium iron phosphate batteries, and has overcome and continuously overcome one application difficulty in energy storage systems.


Gslibatt try to reduce costs and achieve large-scale applications

In the lithium-ion battery cost structure, the material cost accounted for nearly 75% of the total cost, including labor costs, manufacturing costs, and other costs, accounting for 25% of the total. According to the cost distribution, Gslibatt (hereinafter referred to as Gslibatt) has adopted targeted cost-reduction measures:

Gslibatt uses fully automated equipment. This is a measure taken to reduce manufacturing costs and labor costs. Compared with pure hand-made products, production efficiency has increased by more than 50%, manufacturing costs have dropped by more than 7%, and labor costs have dropped by about 2%. The application of automation equipment has reduced the overall cost of lithium iron phosphate batteries by about 10%.

The standardization of other materials and continuous optimization of the process. In addition to other battery materials such as positive and negative electrode materials and separators, and PACK materials, Gslibatt uses standard materials as much as possible, so that when batteries and battery packs are mass-produced, the cost can be greatly reduced, and in the process On the constant optimization. In 2015, Gslibatt reduced overall costs by about 12% in material standardization and process optimization.


Through the improvement of the main raw materials, the cost of the main material is reduced. Through the improvement of formula and process improvement, Gslibatt continuously improved the utilization rate of main materials, and the cost of main materials also decreased greatly. Although the prices of main materials have continued to rise since 2015, the cost ratio of Gslibatt's main materials has not risen and has declined slightly.


The good consistency and long service life play a key role in the cost reduction of the energy storage system during actual use. Because Gslibatt uses full-automation equipment, it has been guaranteed in consistency and matchmaking. In addition, Gslibatt and other original technologies have made the lifespan of energy storage systems more than 5,000 times, which greatly reduces the actual operating costs.


Gslibatt has also obtained key technology, and our lifepo4 battery pack system has greater advantages.

In addition to the above-mentioned targeted cost-cutting measures,Gslibatt has also formulated a corresponding system on how to reduce quality costs and after-sales costs. With the reduction of all costs, Lithium Iron Phosphate Energy Storage System has greater advantages and lays a good foundation for more extensive use of energy storage systems.

The energy storage system scheduling algorithm is the key to whether it can play the best role of the energy storage system. The general battery energy storage system is mainly composed of an energy storage battery, a converter, a control device and a transformer. Figure 2 shows the circuit topology of the energy storage system.

Taking the peak load filling function of the battery energy storage system as an example to illustrate the control algorithm, the first is to forecast the daily load curve and optimize the optimal charge and discharge strategy for 24 hours, ie, whether the battery is charged and discharged at each moment, and the charging and discharging What is the power size? The second is real-time control. According to the charge-discharge strategy given in the current optimization, as well as the current load value and battery status, the charge-discharge power command is calculated and issued to each group of batteries.


The simpler method of peak load shifting is based on the constant power charge and discharge method, which means that the battery energy storage station is charged and discharged at a constant power during the charge and discharge phase. The general step of the constant power charge and discharge mode is to calculate the total charge time and the total discharge time T=S/P according to the battery capacity S and the set charge/discharge power P. Then find the minimum load point and the maximum load point in the load curve, and determine the charging and discharging time.


If it is necessary to flexibly formulate the operation strategy of the energy storage power station according to actual conditions, and if it is reasonably accurate, it is necessary to use the peak-differentiation and valley-filling method based on the power differential charge-discharge method. The power differential charging and discharging method is based on the existing load forecasting curve. Considering the limitation of the battery capacity and the charging and discharging power, the upper and lower limit values of the charging and discharging power for peak load filling and valley filling are first determined, and then performed with the predicted load power curve. Based on this comparison, the charge and discharge power in each period can be determined.

The above is just an explanation of the need for a reasonable algorithm for peak load filling. In addition, there are many control strategies to consider in energy storage systems:

(1) Complementary control strategies for intermittent renewable energy sources and energy storage systems;

(2) Control strategies for island-type energy storage systems;

(3) (3) Neural network algorithms for regional load prediction...

A series of control algorithm strategies for energy and energy, energy, and load are the prerequisites for ensuring stable and reliable operation of energy storage systems and reducing abandonment of wind. Gslibatt has designed targeted algorithms in this respect to deal with energy storage systems under different application conditions.


The selection of single cells and the choice of series and parallel connections determine the reliability and life of the energy storage system. In the battery energy storage power station system, the energy storage battery is connected to the DC bus by a plurality of batteries after being connected in series and then the DC bus is connected to the transformer via the DC/AC inverter, and the AC bus is connected to the grid. In general DC/AC inverter input DC voltage is more than DC500V. When using lithium iron phosphate battery as energy storage battery, the number of strings is about 200 strings. The energy storage capacity required for a MW-class energy storage system may reach more than 1000 Ah. At present, lithium iron phosphate single-cell batteries are mainly dozens of Ah. Therefore, when a higher-capacity energy storage battery pack is to be obtained, a plurality of battery packs need to be connected in series, and a parallel connection method must be adopted to increase the capacity.

In the process of series-parallel connection of the battery module groups, since the series batteries are charged or discharged at the same time, the consistency of the batteries in the series process is very important. When used in parallel, when power changes, start-stops, and other protection mechanisms work in the charge-discharge process, cross-charges between parallel modules and other effects occur. Therefore, the points considered by the Gslibatt Storage System battery include:

(1) Whether the single battery can meet the performance requirements of the working process;

(2) How to achieve the consistency between the battery module and the entire battery;

(3) Whether the single battery and the battery module can meet the power during charge and discharge When changes, start-stops, and other protection mechanisms work, the effects of paralleling cells and modules are suppressed;

(4) When the battery's internal mechanism changes with the passage of time, it can meet the above-mentioned process performance requirements;

( 5) Use the first string and then the first string and then the first string.


After taking the first string and the first and second string, there is a big difference. According to Fig. 3, it can be seen that the first string is followed by security and reliability; and the capacity is smaller and the self-discharge is greater, and the BMS is more demanding. If you use first and then after the string is the opposite.

Gslibatt has a professional single cell battery testing and module PACK team. It has been doing in-depth research on battery strings and parallel connections in energy storage systems. Taking the above considerations as the starting point for the project, the battery string parallel connection and assembly process are systematically defined.

How the Battery Management System (BMS) balances the individual cells should be solved. The above-mentioned consistency of the battery is very critical, but there will always be differences among the battery cells, and the difference will increase with the use of time. As an important part of the battery pack, how the battery management system (BMS) should balance the cells is an indicator of the longevity of the energy storage system.


The long-term research of Gslibatt Energy Storage shows that the consistency of the battery is determined by the consistency of many parameters; the consistency presented at different operating currents is not the same; the consistency caused by differences in materials and processes is very different; There are essential differences between batteries at different times and using different experiences.

According to the above research findings, targeted design of BMS equalization function is targeted, which avoids the imbalance caused by the differences in this system, rather than simple passive equilibrium or active equilibrium. Because the so-called passive or active equilibrium is only based on the monitoring voltage, there is a deviation from the source. Of course, the hardware and algorithm of the balanced part of the BMS designed by Gslibatt must be properly adjusted in accordance with the actual work requirements, usage, and environmental requirements of the energy storage system.

Lithium-ion battery and BMS system and PCS matching problem. The energy storage converter (PCS) serves as an energy execution system and is responsible for various energy conversions and charging the battery system. Therefore, how to better match the battery system during use is the key to making the energy storage system safe, stable, and reliable. Usually the PCS mode is:

1) Power mode: reference to the set active power and reactive output power;

2) FM mode: set the frequency, absorb or send active power according to the frequency setting value to adjust the system frequency;

 3) regulator mode: set Set the reference voltage and inject capacitive or inductive reactive power according to the voltage setting (low voltage ride through, STATCOM);


Island mode: from the big grid, self-networking operation, frequency regulation, synchronization and synchronization. In different modes, the battery and the BMS are in different working conditions, and may have different special conditions such as charge, release, standstill, balance, and pulse exchange. Therefore, how to control the voltage and current in the BMS to stabilize the transition, how to balance the PCS charge and discharge, how to use the communication and control strategy between the BMS and the PCS, how to make the BMS and PCS their respective protection mechanisms accurately and cleanly implemented, etc. Must be fully considered. Gslibatt is embarking on the establishment of various large databases for continuous analysis and summary, so that lithium-ion batteries and BMS can be more effectively matched with PCS.


During the continuous development and practice of energy storage systems, Gslibatt designed corresponding solutions to some of the above practical problems, and further implemented other remote monitoring, cloud management systems, big data collection and analysis, and energy storage battery recycling. The actual development and application. This will continue to be applied and promoted in future power station energy storage, home energy storage, communication energy storage and other different energy storage systems.


Normally battery pack capacity for the storage system is24v 200ah 5kwh, 48v 100ah 5kwh, 48v 200ah 10kwh,48v 300ah 15kwh. Or ESS 48V 10AH ,ESS 48V 20AH ,ESS 48V 30AH , ESS 48V 50AH,etc.