Power battery self-discharge detecting and grading process

Abstract

The invention relates to a power battery self-discharge detecting and grading process. The process comprises the following steps of: carrying out capacity grading on formed batteries and recording discharge capacities as C1; carrying out high-temperature aging on the capacity graded batteries at a temperature of 40-80 DEG C for 3-7 days; carrying out capacity keeping rate test on the high-temperature aged batteries, recording the discharge capacities as C2, calculating ratios K of C2 to C1, selecting batteries with relative large self-discharge through the K and grading the other batteries, wherein the batteries, the K of which is smaller than or equal to R, are batteries with large self-discharge, namely, unqualified batteries, and the batteries, the K of which is between R and 100, are divided into N grades according to the K; and carrying out stock removal on the graded batteries according to the grades. According to the process, batteries with relatively large self-discharge can berapidly and effectively selected, and the batteries are divided into different grades during the detection, so that the grading process of module grouping sections is saved.

Description

technical field [0001] The invention relates to the screening and grouping of lithium ion batteries, in particular to a lithium ion battery self-discharge detection and grouping process. Background technique [0002] Lithium batteries are more and more widely used in mobile phones, power tools and other products. Due to the low voltage and capacity of lithium battery cells, multiple lithium batteries must be connected in series when used in tools to meet the requirements of these tools. This requires that the consistency of these single cells connected in series is very high. [0003] When the battery is not connected to the external circuit, the battery capacity loss caused by the internal polarization reaction is generally called self-discharge. Expressed by the percentage of capacity lost per year or per month, for example, the self-discharge of various lithium-ion batteries is very small, about 1-2% per month, and that of metal hydride batteries is as high as more than...

AI Technical Summary

Problems solved by technology

[0004] In the production process of lithium batteries, there are currently two ways to screen batteries: 1. The battery is charged to a half-electric state, and it is selected after storage for a period of time. Obviously, it is difficult to pick out, and the required storage time is long; 2. After the battery is divided and discharged (discharged to 2.0 or 2.5V), after a period of storage, the rebound voltage is detected and selected. This method has a short storage time. The process time can be shortened, but this method has high requirements for product processing consistency. Due to the inconsistent polarization state during the battery discharge process, some batteries cannot judge self-discharge by rebound voltage.

[0005] Patent 2014103502724 discloses a lithium battery self-discharge screening method. The invention precharges the lithium battery and records the total battery capacity C1; the battery is aged at a constant temperature; the aged battery is discharged at a constant current in a normal temperature environment, and then Charge the battery with the same constant current, respectively record the capacity C2 after constant current discharge and the capacity C3 after charging; calculate the capacity difference δ1=C2-C1, and then calculate K1=δ1 / T1; directly transfer K1 within the qualified range Go to the next process; aging the normal circulation battery at constant temperature; discharge the aged battery at a constant current at normal temperature and pressure, and record the capacity C4 after discharge; calculate δ2=C4-C3, and then calculate K2=δ2 / T2, K2 The battery within the qualified process range is a battery with small self-discharge. This invention uses the change of battery capacity within a certain period of time to effectively select lithium batteries with large self-discharge through two screenings. The process steps are complicated and the screening time is long.

[0006] Patent 201410801779 7 discloses a lead-acid battery formation and assembly process. This invention repeats the charge and discharge of the assembled and internalized battery several times; the battery is charged with constant voltage and current limit, and the battery is pumped during the process; After the acid extraction is completed, put a rubber cap on the acid injection port, connect a group of batteries in series, discharge at a constant current until the average voltage reaches the cut-off voltage, and record the discharge time; the battery packs whose discharge time difference is less than the set value are classified as the first file , detect the battery voltage, group the batteries of the same level according to the voltage; after the grouping is completed, charge the battery pack, the invention selects the battery in the range of flat voltage, but the voltage and capacity of the battery in this range do not change significantly , it is difficult to pick out, and the required storage time is long