Calculation method of the capacity of the battery

In small capacity UPS, in addition to the standard itself around 30 min co., LTD battery matches outside quantity, users often need to extend battery backup time, generally in the large capacity of UPS, no standard battery, but according to the needs of the match. These need to choose the battery capacity, but generally does not correct battery capacity calculation alone can get. Reason is the discharge current of the battery if more than the threshold value stipulated in the discharge rate can appear nonlinear, that is to say, the discharge current and battery voltage no longer maintain linear relationship, so need to calculate and check the table or curve with the combination of methods to determine the battery capacity.

Using the constant current discharge curve to determine the battery capacity

Before the check curve, first calculate the discharge current value Id

Type of Id - discharge current (A);

S - UPS power rating (VA);

F - the load power factor, F 1 or less;

Eta - inverter efficiency, eta 1 or less;

K - load utilization coefficient;

Umin moments before - UPS power off the battery voltage (V).

Case 1: a 10 kva load power factor is 0.8, mains power request delay after 8 h. The user require the use of 100 ah battery, need how many?

Solution: choose according to the requirements of a nominal value is 15 kva UPS, inverter efficiency eta = 0.95 is known, 16 12 v batteries, dc voltage with load utilization coefficient k 1.

Often have this kind of circumstance, suppliers to reduce prices, improve competitiveness, without authorization, chose load utilization coefficient is small, and give a "according to", in the case of initial user puzzled, head start. To the user after the compatibilizing planted hidden dangers. Generally this load utilization coefficient k should be chosen by the users themselves. It is advisable to suppliers to choose 1.Calculated on general situation, the rated dc voltage should be

Un=12V×16=192V(2)

Float charging voltage for Uf = (2.25 x 6) x 16 = 216 (V) (3)

Inverter shutdown voltage for Umin = (1.75 V x 6) x 16 = 168 V (4)

First of all, according to the type (1) the discharge current of full load when the Id:

Why Umin is adopted in the on type, not the Un or Uf? This is because the battery discharge to the minimum voltage Umin makes inverter power off, that is to say, the inverter shutdown and Umin only,

The meaning is: before the UPS power off moment still can provide 100% of its power. To illustrate this problem, the Un and Uf In type (1), and the corresponding discharge current: = 44 In a, If = 39 a.

Whether to draw the discharge current in amperes multiplied by the required time is battery backup always Ann hours? There are a number of users is doing so. With three different current value and reserve time to multiply by the following three battery capacity:

Cn = 44 a x 8 h = 352 ah, the total capacity of Cnt = 352 ah x 16 = 5632 ah

Cf = 39 a x 8 h = 312 ah, the total capacity of Cft is = 312 ah x 16 = 4992 ah

Cd = 50.13 A x 8 h = 401 ah, the total capacity Cdt = 401 ah x 16 = 6416 ah

The above three total capacity value is far difference between each other, especially between the Cdt and Cft is sent 1424 ah, on the UPS battery is a difference of 15 day! If section 100 ah battery meter by 800 yuan, 12000 yuan, now 15 kva UPS about 40000 yuan, this is about a third of the price of UPS. Particularly noteworthy is due to battery capacity difference, will confuse the user: exactly which capacity value right? Which one battery capacity value to meet the requirements? Battery capacity is small while prices to fall, but planted users suffer losses.

Above is just the difference between the capacity caused by some worry, because the battery capacity has not yet been finalized, which is to is wrong needs further analysis. Due to the battery discharge current increases when the discharge regularity is nonlinear, calculate alone is not the correct results. So still need to check discharge curve is shown in figure 1, it is Panasonic battery100 ah discharge curve, can be seen from figure 1, there are four different temperature of the discharge curve, from left to right, in order to 15 ℃ and 0 ℃, 25 ℃ and 40 ℃.As an example, just check a curve corresponding to 25 ℃.There are two types of check method: by the time check current method and the current time.

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