The rechargeable lithium batteries evaluation is divided into two parameter systems: self-evaluation and comparative evaluation. Self-evaluation is to evaluate part of the performance of a brand of rechargeable batteries, while comparison evaluation is to compare two or more brands of batteries with the same nominal capacity on a certain performance parameter. Rechargeable battery evaluation is an important means to describe the objective condition of the battery. In general, rechargeable battery evaluation requires special testing equipment, so it is better to test it in the laboratory, which can reduce errors.
Whether it is self-evaluation or comparison evaluation, there are two prerequisites for rechargeable battery evaluation. One is that the working temperature is within the normal temperature range, and the other is that the rechargeable battery must be new.
For self-evaluation in rechargeable battery evaluation, the focus of battery manufacturers is often not exactly the same: some include all performance parameters, some only test parameters related to capacity, and some will add safety performance on this basis. test.
However, for the comparative evaluation, it basically revolves around the parameters related to capacity. The prerequisites at this time, in addition to all new batteries, should pay attention to the consistency of all setting conditions, such as temperature, current, voltage, rest time, number of cycles, test cabinet model, etc. All rechargeable battery evaluation environments must be the same of.
In the comparative evaluation, three parameters are mainly tested:
- The actual capacity of the battery and its difference from the nominal capacity. The actual capacity of the evaluation is based on 0.2C discharge. Within the specified number of cycles, the weighted average of each recorded power is used as the actual capacity. The closer the actual capacity is to the nominal capacity, the more “true” the battery is.
- Evaluate battery life. On the basis of the actual battery capacity evaluation, the actual capacity of each battery is compared with the nominal capacity one by one, and the respective capacity decay rate is obtained to evaluate the battery life.
- Evaluation of self-discharge: take a certain period of time as a rechargeable battery evaluation cycle, and keep it to the cut-off voltage of the rechargeable battery to see the battery capacity change during the period. Attention should be paid to this process: each brand should select several batteries, because there is a problem of battery discharge balance. Even if the overall self-discharge of different brands of rechargeable batteries is similar in the rechargeable battery evaluation results, a battery with poor consistency can be considered to have poor long-term capacity to retain power.
Rechargeable battery evaluation is a serious and scientific work. The staff should not only record the data of rechargeable battery evaluation, but also strengthen the data processing and digital analysis capabilities of rechargeable battery evaluation, so as to better provide accurate services for battery users.