First, take a look at the battery cells whether they are of grade A quality or not. The quality of the cells determines the quality of the battery pack. Cells parameters such as voltage, capacity, resistance, etc, the more consistent are, the better quality the cells are. And the cells are better produced by big cell manufacturers. Big cell manufacturers have advanced production equipment, qualified technical staff, and standard management. All these contribute to cell quality.
Second, a good BMS is also an important indicator to measure the performance of lithium-ion battery packs. BMS has the basic function of over-charge protection, over-discharge protection, over-current protection, over-temperature protection, anti-reverse charging protection, and cell balancing function. BMS has a hardware version and software version. The hardware version does not have the function of communication which is suitable for light-duty electric vehicles, such as electric bikes, electric scooters, etc. Software BMS has the function of communication, usually by RS485 or CAN. No matter the hardware version or software version, you'd better buy from big BMS manufacturers.
Third, find a big lithium battery pack manufacturer because of its stable supply chain, mature production technology, and after-sale service is guaranteed.
Four, take a look at the price. The reference price of lithium battery packs by 2021 is 1300-2000 RMB/KWH. Below 1100 RMB/KWH is not grade A quality. Well, the price of lithium-ion batteries will decrease gradually over time. But in the year 2021, the price seems won't go down since every material cost is increasingly going up. YM Power Tech Limited will keep updating the info in later news.