Maintenance free battery capacity calculation

Battery capacity is one of the important performance indicators to measure battery performance. It indicates the amount of electricity discharged by the battery under certain conditions (discharge rate, temperature, termination voltage, etc.) (discharge test can be performed with js - 150 d), that is, the capacity of the battery, usually In ampere-hours (abbreviated as ·H, 1 c·H = 3600).

The battery capacity is divided into actual capacity according to different conditions. The theoretical capacity and rated capacity, the calculation formula of battery capacity C is C = ∫t0It1dt (I integrate the current in t0 to t1 time), and the battery is divided into positive and negative poles.

Battery capacity unit

Usually, we say that the battery capacity is in ampere-hours, which is based on a certain battery that has been determined.

For example, we say the battery capacity of this mobile phone; the battery capacity of this battery car is different for different batteries. For the battery voltage has been determined, without considering the actual voltage, it is only necessary to say that the battery capacity can be represented.

However, for batteries of different voltages, we can't simply use the ampere to represent the capacity, such as a 12 v20ah battery, a 15 v20ah battery, even if it is 20 ah, the same power load, the device can work normally, but The duration is different, so the standard capacity should be in work.

For another example, a device can support 12 v, and can also support 24 v. It can be powered by a 12 v (20 ah) battery and can provide one hour. Then two series will become 24 v (20 ah). There is no increase in time, but the duration will be doubled. Therefore, the capacity should be considered as the work contained in the battery at this time, and it should not be considered a safe time.

W (work) = P (power) * T (time) = I (current) * U (voltage) * T (between)

This discussion of battery capacity has practical significance and must be realistic. Otherwise, there may be a saying that a mobile phone battery is larger than the battery capacity of a battery car. This is obviously unscientific.

Battery

Battery calculation method one

The capacity of the battery must be the rated voltage that can be supplied to the load for a given period of time. The capacity calculation method will be described below. 1, the necessary conditions for calculating the capacity, the discharge current is necessary to determine the increase and decrease of the discharge process and its changes with time. B, the maximum time C of the expected load of the discharge time, the minimum battery temperature pre-estimates the temperature condition of the battery placement place and determines the minimum value of the battery temperature. It is usually 50 C when it is indoors and -50 C when it is set inside a special room. Use the air conditioner to ensure the indoor temperature as the lowest temperature. D, the lowest voltage allowed in the lowest voltage cell (V / single cell) = (the lowest voltage allowed by the load + the voltage loss of the wire) / series number 2 , Capacity calculation formula C = 1 *(K1I1 + K2(I2-I1),,,KN(IN-IN-1)]/ LC: 250 C rated discharge rate conversion capacity (ah), UXL battery is 10 hours Capacity. L: Correction value used for capacity change due to maintenance factor, number of years of use, and change in usage conditions. General L value is 0.8.K: discharge time T, minimum battery use temperature, minimum allowable voltage And the determined capacity conversion time, I: discharge current subscript 1, 2, nurse: in the order of discharge current change to T, K, I3, the calculation of the capacity, discharge current 140 (certain) B, discharge time 30 minutes C, the minimum battery temperature -550 cd, the minimum voltage allowed is 1.6 V / single cell according to the above conditions, from Figure -11, K = 1.1 C = 1 x1.1x140 = 192 (ah / 10 hours) / 0.8 so, You can use UXL220-2. Note: The above example is for the calculation of the battery capacity of a simple load type with a certain discharge current. For the calculation of other load types, please refer to Japan. Battery industry standard [SBA6001].

Battery calculation method two

Algorithm for 10 UPS battery capacity for 109 ah block / kVA design life

When using, calculate according to the following formula: required battery capacity (ah) = UPS capacity (KVA) × 109 (ah. block) / kVA / number of battery blocks per group, For example, a 120 KVA UPS, each group of batteries 32 Block, requires a backup time of 60 minutes (ie 1 h). The required battery capacity is 120 KVA × 109 ah 13080 / KVA = a block, 13080 ah / 32 blocks = 409 (ah), that is, optional 12 v, 100 ah battery 4 groups (32 blocks / group). Note: The actual backup time is less than 60 minutes (lack of a point). If each group has 33 blocks, then 13080/33 = 396, and the same 12 v, 100 battery packs (33 blocks/group) are also available. Note: The actual backup time is more than 60 minutes (more than one point). If the backup time is required to be 30 minutes, then 109×120 = 13080, 13080/32 = 409, 409/2 = 205. Since the discharge power and discharge time of the battery are not linear, that is, it cannot be simply divided by 2, and the correction factor is also multiplied, as shown in Table 1, so 205 × 1.23 = 252 ah. That is, optional 12 v, 65 ah battery 4 groups (32 blocks/group). Note: The actual backup time is more than 30 minutes (more than one point). If the backup time is required to be 20 minutes, then 409/3 = 136, you need to multiply by the correction factor, 136 × 1.41 = 192 ah, that is, optional 12 v, 65 ah battery 3 groups (32 blocks/group). Note: The actual backup time is more than 20 minutes (more than one point).

4200 mAh = 4.2 amperes, can be discharged for 4.2 hours according to 1 amp discharge. It is generally recommended to use 1/10 ampere current discharge as a reference.

It can be discharged for 10 hours at a rate of 4.2 x 0.1 = 0.42 ampere per hour. It can be discharged for 5 hours at a rate of 0.84 amps per hour, and so on. It is recommended that it should not be placed too large to avoid damage to the battery.

According to the power formula P = UI, the current is 3÷3.7 = 0.811A, and then the total battery capacity is 4.2A, 0.811A = 5.18 hours. Are you satisfied with the final 5.18 case?

The charging formula is as follows:

Charging time (hours) = (battery capacity / charging current) * (1.2 ~ 1.5)

The charging current can be as small as 1.5 times, otherwise, 1.2 times is basically sufficient.

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