Introduction to lithium ion battery internal resistance and capacity detection method

Forfatter: Iflowpower – Fournisseur de centrales électriques portables

Detecting the meaning of lithium-ion battery: 1, one of the projects of the factory inspection; The larger the internal resistance, the smaller the internal resistance, can be determined according to the internal resistance size; 4, the aging manifestation of lithium ion battery after the aging and expiration of the expiration is increased in internal resistance, so detecting the battery internal resistance can quickly determine the battery. The degree of aging; 5, during the maintenance of the lithium ion battery pack, the internal resistance of each battery unit is often detected, so that the unit of the internal resistance is picked up, change it. Lithium-ion battery internal obstruction method: According to physical formula R = U / I, the detection device allows lithium-ion batteries to force the lithium ion battery to force through a large constant DC current (currently 40A ~ 80A's large current, measure the voltage at both ends of the lithium ion battery at this time, and calculate the current lithium-ion battery in accordance with the formula.

1. Measuring the open circuit voltage of the battery: U12, the battery is connected in parallel: R, discharge; 3, measure the voltage between the battery during discharge of lithium ion battery: u2; 4, calculate the internal resistance: r = (U1-U2) / (U2 / R) For example, a battery open voltage is 12V, and a 10 ohmic resistor is lowered to 10V, the internal resistance of the battery is: r = (U1-U2) / (U2 / R) = (12-10) / (10/10) = 2 ohms. Normally, the larger the internal resistance r of the lithium-ion battery, the worse the load of the battery, and the internal resistance R of high-power batteries (such as the battery) is usually very small.

The internal resistance of small power batteries (such as 9V stacking batteries) is usually relatively large. AC pressure drop internal resistance method: Because the lithium ion battery is actually equivalent to an active resistance, we apply a fixed frequency and fixed current to a lithium ion battery (currently using a 1kHz frequency, 50mA small current), and then The voltage is sampled, and the internal resistance value of the lithium ion battery is calculated after a series of resolution of rectification and filtering. The lithium-ion battery measurement time of the alternating internal resistance measurement method is extremely short, usually about 100 milliseconds.

The accuracy of this measurement method is also good, and the measurement accuracy error is generally between 1% to 2%. Lithium-ion battery capacity detection method: lithium ion battery capacity detection is parameter with a full charge voltage and setting, because the lowest discharge voltage of the lithium ion battery is 2.75V, so the voltage of less than 3V has been pair of lithium ion batteries It is meaningless; the fixed current discharge is generally used, and the lithium ion battery is generally detected by 0.

5C discharge. 1. Ocean the battery, the voltage after the single lithium ion battery is filled with 4.

2V; 2, use the multimeter to make the lithium ion battery constant current 0.5c, and the corresponding battery capacity is discharged, the termination voltage is set to 3V; 3, multiplying the time of the discharge of constant current is the battery capacity; inspection: If the constant current discharge does not reach two hours, the nominal voltage is not enough, the lithium ion battery has the possibility of counterfeiting. .