How to calculate the capacity of the battery

Calculation method

Battery capacity is now typically calculated using a 10 hour discharge rate. The discharge current is set to I10 (10% of the nominal capacity), the discharge termination voltage is set to 90% U (90% of the nominal voltage), and the discharge starts. If the battery does not reach the termination voltage after 10 hours, the battery capacity is 100%, if it reaches 5 hours and reach the termination voltage, indicating that the capacity is only 50%, and so on.

Battery Introduction

A device that converts chemical energy into electrical energy is called a chemical battery, and is generally referred to as a battery. After discharge, the internal active material can be regenerated by charging - storing electrical energy as chemical energy; and converting the chemical energy into electrical energy when discharging is required. Such a battery is called a battery (storage battery), which is also called a secondary battery. The so-called battery is an electrical chemical device that stores chemical energy and discharges electric energy when necessary.

Battery capacity calculation method

The capacity of the battery must be the capacity that can be supplied to the load at a given voltage and for a predetermined period of time.

The capacity calculation method will be described below.

1. The necessary conditions for calculating the capacity

A, discharge current

It is necessary to clarify the increase and decrease of the load current during discharge and its change with time.

B, discharge time

The maximum time the load can be expected.

C, the lowest battery temperature

The temperature condition of the battery placement place is estimated in advance, and the minimum value of the battery temperature is determined. It is generally 50C when it is indoors, and it is -50C when it is set indoors in a particularly cold area. When the indoor temperature is used to ensure the indoor temperature, the actual temperature is taken as the lowest temperature.

D, the lowest voltage allowed

The minimum voltage allowed in the cell (V/single cell) = (the lowest voltage allowed by the load + the voltage loss of the wire) / series number

2. The calculation formula of capacity

C=1*[K1I1+K2(I2-I1), ,,KN(IN-IN-1)]/L

C: 250C rated discharge rate conversion capacity (AH), UXL battery is 10HR capacity.

L: Use for capacity changes due to changes in maintenance factor, number of years of use, and usage conditions

Corrected value: The general L value is 0.8.

K: capacity determined by the discharge time T, the minimum use temperature of the battery, and the minimum allowable voltage

Conversion time

I: discharge current

Subscript 1, 2 to N: sequentially added to T, K, I in the order of discharge current change

3. Calculation example of capacity

A, discharge current 140A (certain)

B, discharge time 30 minutes

C, the lowest battery temperature -550C

D, the minimum voltage allowed is 1.6V/single grid

According to the above conditions, from Figure-11, K = 1.1

C=1X1.1X140=192(AH/10HR)/0.8

Therefore, the UXL220-2 can be used.

Note: The above example is for the calculation of the battery capacity of a simple load type with a constant discharge current. For the calculation of other load types, please refer to the Japanese battery industry standard [SBA6001].

The capacity of the battery is usually expressed in amps and hours (abbreviated as AH, 1A.h=36000C). The calculation formula of the battery capacity C is C=I∫t0tdt. The battery capacity is divided into actual capacity, theoretical capacity and rated according to different conditions capacity. The minimum capacity to be discharged at a certain discharge rate at 25 ° C to the termination voltage is the capacity of the specified battery at the time of design and production. This is called the rated capacity of a certain discharge rate RH. The battery capacity is generally calculated in AH (ampere-hours), and the other is calculated in CELL (unit plate) several watts (W). (W/CELL) 1. AH (ampere hour) calculation, defined as 20 hours. For example, a 7AH battery refers to a continuous discharge current of 0.35 A for 20 hours in a row. 2. W (power consumption) / CELL (unit plate)) calculation, the definition is based on 15 minutes. For example, 1221W battery is 12V (6CELL), each CELL power supply 21W can supply power for 15 minutes. 3. The charging time is based on 10 hours, and the charging current is 1/10 of the battery capacity. Fast charging will reduce battery life. Battery capacity refers to the amount of battery storage. The unit of battery capacity is “MAH”, and the Chinese name is MAH (when measuring large-capacity batteries such as lead storage batteries, for the sake of convenience, it is generally indicated by “Ah”, the Chinese name is Anshi, 1Ah=1000mAh). If the rated capacity of the battery is 1300mAh, if the battery is discharged with 0.1C (C is the battery capacity), that is, 130mA, then the battery can work for 10 hours (1300mAh/130mA=10h); if the discharge current is 1300mA, then the power supply The time is only about 1 hour (the actual working time varies depending on the individual differences in the actual capacity of the battery). This is an analysis under ideal conditions. The current of a digital device in actual operation cannot always be constant at a certain value. (Take digital camera as an example, the working current will change greatly due to the opening or closing of LCD display, flash and other components), so the battery can only provide a certain value for the power supply time of a device, and this value can only be estimated through practical experience.

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