Method of Measuring the Capacity of Lithium - ion Batteries with a Multimeter
Strictly speaking, a multimeter can only measure current, voltage, and resistance, and it cannot measure the capacity. However, it can be used to roughly determine whether a lithium-ion battery has insufficient capacity. That is, use the DC current range of the multimeter (a pointer multimeter is preferably used). Instantly measure the positive and negative polarities of the battery. If the current shown on the meter is large, it indicates that the battery has capacity. If the displayed current is very small, it means that the battery has insufficient capacity. But this method is a destructive measurement method. In fact, it is equivalent to short-circuiting the battery for a look. Therefore, the contact should be made and broken at any time during the measurement. It is absolutely not allowed to keep it connected for a long time. Otherwise, even a good battery will have its power drained.
Originally, a multimeter is not suitable for measuring the capacity of lithium-ion batteries, but it is not impossible to measure, just that it is not professional. Here is an introduction to the method of measuring the capacity of lithium-ion batteries with a multimeter.
Equipment: Multimeter, small light bulb or high-power resistor, timer or mobile phone.
After the battery is fully charged, leave it idle for 2 hours, measure the no-load voltage and record it. Connect a small light bulb or resistor and measure the current. It is best to control the current to about 1/10 of the capacity. Measure the current every 1 hour. You can also measure the voltage and then convert it into current. When the voltage is approaching 3.2V, measure the current and voltage every 10 minutes. Stop the measurement until the voltage drops to the protection voltage to prevent damage to the battery caused by over-discharging.
Add up all the products of current and time, and then you can get the capacity of the lithium-ion battery.
This is a more accurate measurement. For a rough measurement, you can consider the current as constant and directly use the middle value of the current multiplied by the discharge time.
A multimeter cannot accurately measure the capacity of a battery.
However, some people will use a multimeter to test the magnitude of the short-circuit current of the battery to roughly determine the capacity of the battery, and use this method to pair battery packs of the same specification, and the effect is acceptable. But for some batteries, the open-circuit voltage is normal, and once the short-circuit current is measured, their true situation will be revealed.
Measuring the short-circuit current (assuming that the current value is within the allowable range of both the multimeter and the battery) can only be used to compare the power levels of batteries of the same model. Batteries of different models cannot be compared because the standard internal resistances of batteries of different models are different. Even if the stored power is the same, their short-circuit currents are different.
