The productivity and reliability of an energy storage system is largely dictated by the quality of its various components, not least the battery cells themselves. Prismatic cells are a popular choice in energy storage systems (ESS), and if the companies that install them want their systems operating at maximum effectiveness, they will want to sort cells before they are integrated into cells. In this article we find out why it’s important for energy storage companies to sort prismatic cells before they complete their systems.
The Low Down on Prismatic Cells
Prismatic cells are widely used in energy storage systems where space is at a premium and higher density, higher power output cells are needed. The rectangular shape of these prismatic cells allows these cells to be arranged more efficiently than the less space efficient cylindrical cells of similar chemistry. Prismatic cells are found in electric vehicles (EVs) and for other places where high-performance energy storage systems can fit.
As you can imagine, slight variances in battery construction, in materials of various cells, and in environmental conditions lead to small variations from identical cells in terms of thing like capacity, voltage, and internal resistance from cell to cell. Though these discrepancies are small in sections, they make a significant difference in performance given the rest of the conditions described. This is where sorting comes in.
1. Voltage and Capacity UniformityDo Cells with Different Capacities yield the same Voltage?
Cells having unequal charges may not discharge and charge correctly. Cells with a smaller capacity may be wrongly charged with too much current or deep discharged, equalising thereby their lower charge, thereby destroying their capacity at the expense of the whole system; by sorting the cells according to their volts and capacity, each pack is gotten up, if not all of the same height, at least using all cells working at maximum, instead of cells that are not.
2nd. To Make the Battery Pack Safe
Lithium-ion batteries are getting into more general use; as we all know, they are hot temperature cells, and unless careful may damage by not having their heat properly arranged. By prismatic cells if sorted and matched according to their resistance and coefficient of capacity will not be unequally warmed, as they are suited to their work by being themselves equal. Cells that may have made the same number of yards run in good time will not have the same tendency to augument heat. Savers of heat are therefore made good batteries for energy storage applications.
3rd. Cause Cell to have a Longer Life
The tendency in energy storage systems is to charge and discharge frequently, and is necessary, especially for light work. The more these cells are kept to this work, and to their value, accomplished without rubbish, the better. To have prismatic cells sidelonged (closely matched) to quite indefinable fractions. By laying them together of the same size, side by side, in a symmetrical manner, this equable application of work will be longer from the cells, and also these cells at equal charge and discharge rates exactly accomplish their work with less wear.Easier Battery Management
Data about the condition and performance of individual cells in a battery pack is vital to battery management systems (BMS). If you start out with prismatic cells that are already sorted to have those characteristics, then the BMS is much better positioned to know what each individual cell is doing. Consequently, the BMS can do a better job overall of managing the system and detecting when something is going wrong from that clear baseline.
Performance in Different Operating Conditions
Energy storage systems are often subjected to the wide variety of conditions typically associated with energy storage from extreme temperatures to widely varying loads. By sorting prismatic cells, energy storage companies ensure that the cells within a system are thermally compatible and generally able to produce the same sort of performance profiles. For example, if some prismatic cells will provide 100A continuously at 25ºC and the others will only do that at 40C, those batteries may end up being prematurely shut down because they will become too hot at that discharge rate. So, for several reasons (both thermal and electrical) sorting fist sized cells is vital. Herein lies the beauty of the generic and matched prismatic cells. If some have lower internal resistance and some of a higher value, they can be sorted, and only those with lower resistance used for metered high drain applications with confidence that they will supply current until all the available energy in the system has been depleted.
The Mechanics of Sorting
Sorting prismatic cells involves measuring voltage, capacity, perhaps internal resistance (though this is beginning to become less relevant) or some measure of impedance and classifying them into categories using an automated machine to do so. Battery sorting and testing machines generally take multiple data points across a range of cells and allow the operator to select good cells to assemble from a group of 12 down to individual cells graded 150Ah, good/better/best.
In their prismatic IC engineered prismatic cells, Lishen use sophisticated smart sorting machines with the best precisiotestable features. These guarantee the thinnest cell design, the lowest space occupation for battery, maximum lifetime; battery sorting and testing.
