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# Analysis of the method of determination of battery capacity

2022/04/08

Author ：Iflowpower – Portable Power Station Supplier

Different industries have different detection standards based on the use conditions. Lithium-ion batteries for 3C products, based on national standard "GB / T18287-2000 cellular telephone lithium ion battery general specification", battery rated capacity detection method is: a) charging: 0.2c5a charge; b) discharge: 0.

2c5a discharge ; c) Five cycles, once it is determined to be qualified. According to the electric vehicle industry, according to the national standard "GB / T31486-2015 electric vehicle power storage battery electrical performance requirements and experimental methods", the rated capacity of the battery refers to the chamber temperature battery with 1i1 (a) current, and reaches the termination voltage. Capacity (AH), wherein I1 is 1 hour rate discharge current, and its numerical value is equal to C1 (a).

The detection method is: a) at room temperature, transdermal press charging when charging at 1I1 (a) current constant flow to the company's predetermined charge, to the charging termination current to stop charging when the charging is reduced to 0.05i1 (a), and then put it on hold after charging 1h. b) At room temperature, the battery is discharged at 1i1 (a), until discharged to the discharge termination voltage specified in the company's technical conditions; c) Meter discharge capacity (in a AH meter), calculate the discharge ratio energy (with a WH / kg); d) Repeat step a) -c) 5 times, when the extract of 3 experimental results is less than 3% of the rated capacity, the experiment can be completed in advance, and the final 3 experimental results are uniform value.

(3) The charge state SOCSOC (StateOfcharge) is a state of charge, indicating the ratio of the capacity of the battery with the capacity of the battery and its fully charged state after a certain discharge magnification. Open-circuit voltage + safety integration method utilizes an open circuit voltage method to estimate the battery initial state charge capacity SOC0, and then utilize the electricity consumption of the battery to operate, the power consumption is the product of the discharge current and the discharge time, then the remaining power is equal to the product. Difference value of initial power and consumption.

Opening voltage and safety integral combination estimation SOC mathematical expression is: where CN is rated;ηFor charging and discharge efficiency; T is battery usage temperature; i is a battery current; T is battery discharge time. DOD (DEPTHOFDISCHARGE) is a discharge depth, indicating a measure of the degree of discharge, which is percentage of discharge capacity and total discharge capacity. The high and low discharge depth is a big relationship with the life of the battery: the deeper the discharge depth, the shorter its life.

Both relationships are SOC = 100% -DOD4) Energy and comparison cells The energy output from the external work is called the energy of the battery, and the unit generally uses WH. In the discharge curve, the calculation formula of energy is: W = u (t) * i (t) DT. When constant current discharges, W = i * u (t) DT = it *ü(üIn order to discharge the uniform voltage, T is the discharge time) a.

The discharge process of the theoretical energy battery is in a balanced state, the discharge voltage retention electric potential (E) value, and the active material utilization is 100%, and the output energy of the battery under this condition is theoretical. Energy, that is, the maximum work made by the inverter battery in constant temperature. b.

Energy actually output when the actual energy battery is discharged is called actual energy, electric vehicle industry regulations ("Dynamic capacity requirements for electric vehicles with GB / T31486-2015 electric vehicles and experimental methods") Discharge, the energy (WH) that is released when the voltage is terminated, and rated energy. c. The energy given by the energy unit mass and the unit volume of the battery, the mass ratio energy or volume ratio energy, also known as the energy density.

The unit is WH / kg or WH / L. The most basic form of the discharge curve is the voltage-time and current time curve, by transforming the time axis, the common discharge curve also has a voltage-capacity (specific capacity) curve, voltage-energy (specific energy) curve, voltage-SOC Curve, etc.