Abstract: with the rapid growth of electric vehicles, a magnitude of power lithium batteries have been the industry opportunity, also the main way to decline the cost of user energy storage system. GMDE’s energy storage system with second-life batteries recycled from vehicle has successfully put into operation, which indicates the cost of energy storage system can decline to 1RMB/Wh, the application of user side energy storage really has commercial value.
Under the background of green energy, electric vehicles have entered the rapid development. As the core component of vehicles, once the capacity of batteries reduce to 80% of the initial, continue voyage course will plummet, so the batteries of electric vehicles must replace in 3 to 5 years. In that case, the use of second-life batteries will also become a hot topic gradually.
According to the national standards, when the EV batteries remove from the vehicles, there also have considerable capacity existed. If these batteries can be re-used in other fields, it will be a good choice whether in economy or environment. But these decommissioned batteries cannot be used directly as imagined. Due to some obstacles of technology, the battery consistency is different from new batteries, which will be a big challenge in packing.
Based on the industrial know-how and technological advantage, GMDE has taken the lead in achieving energy storage projects with second-life EV battery packs in several provinces, such as shanghai, Jiangsu and Zhejiang etc. GMDE General Manager Jianduo Li pointed out that the successful use of second-life EV battery depends on three essentials: without disassembling, group string distributed architecture, shallow charging and shallow discharging.
The primary factor to influence the economy of second-life EV batteries is the degree of disassembly of the battery pack. According to the current production experience, disassembling the whole battery packs into single cell, then screening, matching and reorganizing, due to the complex craft, the cost of recycling will be as high as new batteries, which is not economical to adopt this method. GMDE General Manager Jianduo Li proposed to use the second-life EV battery packs directly, constitute the fundamental energy storage unit through an appropriate control strategy. This method not only simplifies the process, but also saves more than half of the cost compared to new lithium battery.
In technology, solving the consistency of EV batteries through group string distributed architecture. Now large and medium-sized energy storage batteries are basically centralized, but the environment used、charge and discharge intensity, instantaneous discharge and other parameters are various, and the quality of batteries are different, if put them in parallel, there will be many problems. Through group string distributed architecture, put the batteries from the same vehicle into battery packs, with PCS, monitor in string, composed to a basic energy storage unit, then put the units in parallel, forming large and medium-sized energy storage system with different power, which not only can manage the battery packs separately, also can maximum the consistency of batteries.
Secondly, ensure the security and reliable long service life of batteries by shallow charging and shallow discharging. The capacity, voltage and internal resistance etc. of second-life EV batteries will drop quickly under less cycles, the key reason is that SOC and DOD are not controlled well. By controlling the SOC to ensure the stability of single cell voltage and controlling the DOD to realize the stability of the voltage difference between the highest cell voltage and the lowest cell voltage, thus ensuring the long-term stable operation, objectively increasing the security of the energy storage system.
Energy storage system with second-life EV batteries marks the cost of energy storage into 1RMB/WH era. The application of user side energy storage really has a commercial propaganda value.
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