How To Test A Ni-Cd Battery?

Battery Detection Standards

Nickel-cadmium (NiCd) batteries, a robust and widely-utilized type of rechargeable battery, have specific voltage criteria that must be adhered to for quality assurance. For NiCd batteries entering the inspection area, each cell's open-circuit voltage must exceed 1.2V for uncharged cells or 1.25V for charged ones. This voltage standard is critical as it ensures that only batteries meeting these minimum energy levels proceed further in the evaluation process. Moreover, the voltage range for qualification is defined such that a NiCd cell with a voltage greater than 1.15V per cell is considered qualified, while those within the 0.8V-1.14V range are classified as second grade. Cells with voltages between 0.8V and 0.5V are marked as defective, and any cell below 0.5V is categorized as waste. The stringent voltage requirements for NiCd batteries ensure their reliability and performance in various applications.

In addition to the initial voltage checks, ongoing tests on NiCd batteries include capacity detection and self-discharge assessments. During capacity testing, after numbering the batteries and ensuring no signs of alkali crawling or liquid leakage are present, the batteries undergo a series of charge and discharge cycles to evaluate their performance. After the third cycle, the internal resistance of the NiCd battery is measured, which should not exceed 8 mΩ for superior SC batteries. Furthermore, the self-discharge test evaluates the battery's ability to retain its charge over time. A NiCd battery that has been fully charged and left undisturbed for 72 hours should show no more than a 10% decrease in capacity when discharged back to 1.0V per cell. These rigorous testing protocols guarantee that NiCd batteries maintain optimal performance throughout their lifecycle, from initial voltage checks through to final capacity and life tests.

1. Sampling method and Quantity:

Batteries placed in the inspection area are sampled at the AQL-J1 level specified in the sampling standard.The minimum sample quantity of each lot shall not be less than 30 PCS.

2. Battery Appearance inspection:

a. All incoming batteries must be packed in accordance with the requirements of the order, no damage or mismarked or unclear;

b. Printing contents of all battery jackets must meet the requirements of the order, no printing error, backjet, jacket breakage and other undesirable phenomena are allowed.

3. Open-circuit voltage Detection:

A. All incoming battery open circuit voltage must be greater than 1.2V/ CELL (not charged) or greater than 1.25V CELL (charged) (for NI-CD batteries).

B. Battery voltage greater than 1.15V/ CELL is qualified, 0.8V-1.14V/ CELL is second grade, 0.8V-0.5V is defective, and 0.5V is waste (applicable to Ni-CD battery).

C. The open-circuit voltage of ni-MH batteries must be greater than 1.25V when all batteries in stock are shelved for more than 15 days.1.0-1.24V is grade TWO, and below 1.0V is waste.

4. Battery capacity detection:

A. Before the test, the battery should be numbered on the battery first, and phenolphthalein should be used to test whether the battery has alkali crawling, liquid leakage (i.e. redness around the positive electrode cap) and record the open circuit voltage. Before the first charge, the battery should be discharged to a single 1.0V, and then the battery should be charged for testing 0.2C.

B. Charge the battery for 90 minutes and record the highest voltage when charging, set aside for 30 minutes and then discharge to 1.0V/ CELL. Cycle three times to calculate the last discharge capacity.

5.Detection of battery internal resistance:

    A. After charging for 90 minutes for the third time, the battery should be used for 30 minutes to measure its internal resistance with the battery internal resistance tester.

    B. The internal resistance of superior SC batteries shall not be greater than 8 mΩ; The internal resistance of ordinary SC batteries should not be greater than 10 mΩ, and the second level: 12mΩ.

    C. The internal resistance of a premium AA battery must not be greater than 22mΩ, and that of a common AA battery must not be greater than 25mΩ.

6.Battery Self-discharge Detection

A. Charge the battery for 90 minutes and leave it for 72 hours before discharging it to 1.0V/ CE11 to calculate the discharge capacity.1C1C

B. If the actual capacity of the battery is subtracted from the capacity of the battery used for discharge, the capacity decrease shall not be more than 10%.

C. Charge the batteries that pass the capacity test continuously for one month, and then discharge them to 1.0V/ CE11 for more than 56 minutes.

7. Battery overcharge Test:

A. Charge the batteries with qualified capacity for 105 minutes (1C), and test the batteries with phenolphthalein test solution for alkali crawling and liquid leakage.

Discharge(1C) the battery to 1.0V/ CE11 for normal (For NI-CD)

B. After charging 1C for 6 hours, the battery is allowed to have alkali crawling and leakage, but not allowed to have explosion and deformation. Then discharge 1C to 1.0V/CELL. This battery shall be scrapped (no more than 5 batteries shall be sampled each time) (NI-CD)

8.The qualified battery should be charged 1C for 90 minutes, put aside for 30 minutes, and discharge at the following rate (unit: minute)1C

9. Life test standard:

a. The qualified batteries in capacity test should be charged for 75 minutes and shelved for 30 minutes, and then discharged to 0.8V/ CELL with 2C/5C/10C. When the cycle is 100 times, the capacity loss of first-level batteries should not be greater than 5% of the initial capacity.The second best is not more than 10%.(Generally AA type by discharge 2C /SC type by discharge 5C)

b. For the final discharge test life of the battery, continue the test by charging cycle A until the capacity test is less than 85% of the initial capacity.

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