Easy calculation method for UPS battery capacity
1 For 10Ah·block/kVA battery with a design life of 10 years
When using, calculate according to the following formula:
Required battery capacity (Ah) =
For example: a 120kVA UPS, each group of 32 batteries, requires a backup time of 60min (ie 1h). Then the required battery capacity is
120kVA×109Ah·block/kVA=13080Ah·block, 13080Ah·block/32 block=409(Ah), that is, optional 12V, 100Ah battery 4 groups (32 blocks/group). Note: The actual backup time is less than 60min (lack of a point).
If each group has 33 blocks, then 13080/33=396Ah, and 12 groups of 12V, 100Ah batteries (33 blocks/group) are also available. Note: The actual backup time is over 60 minutes (more than one point).
If the backup time is required to be 30 minutes, then 109×120=13080Ah·block, 13080/32=409Ah, 409/2=205Ah.
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, 4 groups (32 blocks/group) of 12V and 65Ah batteries can be selected. Note: The actual backup time is over 30 minutes (more than one point).
If the backup time is required to be 20min, then 409/3=136Ah, also need to be multiplied by the correction factor, see Table 1, 136 × 1.41 = 192Ah, that is, optional 12V, 65Ah battery 3 groups (32 blocks / group). Note: The actual backup time is more than 20min (more than one point).
Other situations, and so on.
2 For 126Ah·block/kVA design life battery for five years
The calculation method and the multiplication by the correction factor are exactly the same as before, except that 109 is replaced by 126 in the above formula.
If the calculation time is more than one hour, divide it by a correction factor after the above calculation, see Table 2.
For example, the backup time of the previous example is 3h, then 109×120=13080Ah·block, 13080/32=409Ah, 409×3=1227Ah; a correction factor is also required, 1227/1.25=982Ah.
According to the principle of conservation of energy, the above method is the same for three-phase/single-phase or single-phase/single-phase UPS. For example, APC's Xiukang UPS requires two groups (32/group) of batteries, and the calculation method is the same. Pay attention to the concept of "Anshi block".
Generally, the high-power UPS is equipped with 32 batteries for each group; the number of parallel batteries should not exceed 4 groups, so as not to affect the current sharing and charging effect of the battery pack.
As can be seen from the above, in general, it is sufficient to remember the three numbers 109 (or 126) and 1.23.
The above is a quick and rough calculation, not very accurate. For accurate results, refer to the battery discharge characteristics given by the battery manufacturer.
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