How to detect the capacity of a lithium battery pack in Nope Lithium Battery

The application of lithium battery packs is becoming increasingly widespread, involving power and energy storage sources, mobile power sources, and backup power sources. Whether the capacity configuration of lithium battery packs is reasonable directly affects the various technical indicators and service life of the batteries. So, how to detect the capacity of lithium battery packs and what standards should be used for detection?

How to check the capacity of a lithium battery pack?

A multimeter, charger, and battery can measure the true capacity of a lithium battery pack. The capacity test is based on the full charge voltage and the set termination voltage as parameters, because the minimum discharge voltage of lithium batteries is 2.75V, so voltages less than 3V are no longer meaningful for lithium battery testing. Fixed current discharge is generally expressed in C, while lithium batteries are typically tested with 0.5C discharge.

Capacity testing method for lithium battery pack:

The first step is to fully charge the lithium battery, and the voltage of a single lithium battery after being fully charged is 4.2V;

Step 2: Use a multimeter to discharge the battery at a constant current (0.5C, relative to battery capacity), with a termination voltage set to 3V;

The third step is to multiply the discharge current by the time of constant current discharge to obtain the capacity of the lithium battery pack;

Inspection: If the constant current discharge cannot reach two hours, then the nominal voltage is not enough. There is a possibility of counterfeit batteries. ：

Multimeter testing method:

1. Charging termination voltage: It is also the no-load voltage, which is the highest voltage when not in operation, usually 4.2V.

2. Working/nominal voltage: It is also the load voltage, and the voltage during normal operation is generally 3.7V.

3. Discharge termination voltage: the voltage at which the battery cannot operate, with different designs of 3V and 2.75V.

To start the test, first use a charger to fully charge the battery, with a full charge voltage of 4.2V. Then use a multimeter as a constant current load, discharge at 0.2C (i.e. 1000 × 0.2=200mA), and set the discharge voltage of the multimeter to 3V. If the discharge time reaches 5 hours, the battery is qualified. Nowadays, lithium batteries can generally discharge up to 2.75V, which is 80% of the discharge depth with 3V as the termination voltage, but can last for 8 hours, indicating that the power of lithium battery packs has been improved.

0.2C is an international standard testing method, but in reality, 0.5C is usually used for testing. In this case, setting the multimeter to a constant current load of 500mA, it takes more than two hours to reach a voltage of 3V to be considered qualified.

The so-called qualified or unqualified mentioned above is relative to the nominal capacity. And nominal capacity=discharge current x discharge time. If the above discharge time is not sufficient, it indicates that the capacity marked on the lithium battery pack is not enough for 1000mAh, which is a false capacity marking behavior and a deception to consumers. Capacity is the core parameter of lithium batteries, and lithium battery manufacturers generally have dedicated equipment for testing to ensure the quality of the shipped products is qualified.

Measuring the capacity of a lithium battery pack usually involves measuring the battery voltage. The charger detects the battery voltage during charging and considers it fully charged when the voltage reaches the specified value. When the voltage of a lithium battery reaches 4.2V, it is considered fully charged. The accuracy of the voltmeter for detecting voltage should reach a precision of plus or minus 1%. Due to overcharging, the lithium battery may be damaged. If you want to monitor battery charging and discharging, there are mature circuits in the book for reference. If you only need to measure it, it's easy to do. Calculate the load resistance based on the capacity, discharge it with standard discharge current, and then check the voltage. As long as it can reach or approach the nominal discharge time, it's fine.

The above is the method for quickly testing the capacity of lithium battery packs. The capacity detection of lithium batteries is carried out through a battery capacity divider cabinet. The capacity of lithium batteries determines the quality of the batteries. We hope that after learning, everyone can arm themselves and buy legitimate, safe, and long-lasting lithium battery pack products.