Translation: Calculation and Case Study of UPS Power Supply Configuration for Standby Delayed Battery Packs

The simplest design of an Uninterruptible Power Supply (UPS) generally consists of a UPS power host, standby DC battery pack, battery cabinet, and accessories. The standby delayed battery pack typically constitutes about 40-50% of the overall composition value. Configuring the capacity and quantity of UPS standby battery packs based on the customer's delayed time requirements is a crucial point in the budget for low-voltage equipment rooms. According to commonly used calculation methods and suitable UPS capacity segments, it can be divided into capacity estimation methods and constant power configuration methods.

Capacity Estimation Method (Applicable to 1-20KVA (load 900W-18KW) UPS mainframe configuration):

① Confirm the UPS Uninterruptible Power Supply mainframe capacity, for example, 6KVA.

② Confirm the required delay time for the UPS power backup battery pack, 2 hours in this example.

③ Calculation formula:

Battery capacity = UPS mainframe capacity (VA) * Delay time (H) / UPS DC voltage (VDC)

62.5AH = 6000VA * 2H / 192VDC

④ In the previous step, 62.5AH is the capacity specification of the battery. Commonly used battery models are 12V17AH/24AH/38AH/65AH/100AH/150AH/200AH. Following the principle of proximity, select 12V65AH as the specification for the standby battery pack.

⑤ Based on the UPS DC voltage of 192VDC, it can be seen that the default number of UPS DC battery packs is 16. The configuration for this 2-hour scenario is a UPS Uninterruptible Power Supply of 6KVA combined with a battery pack consisting of 16 12V65AH rechargeable batteries.

⑥ Attached table: Common configurations for a 6KVA mainframe

Sequence number | Endurance scheme | Battery model | Quantity | Battery cabinet

1 | 6KVA | 6000VA/5400W | 1 | Single host

2 | Half an hour | 12V26AH | 16 | A6*1

3 | One hour | 12V38AH | 16 | A8*1

4 | Two hours | 12V65AH | 16 | A16*1

5 | Three hours | 12V100AH | 16 | A16*1

6 | Four hours | 12V120AH | 16 | A16*1

7 | Six hours | 12V100AH | 32 | A32*1

8 | Eight hours | 12V120AH | 32 | A32*1

Constant Power Configuration Method (Applicable to 30KVA and above (load 27KW and above)):

① Calculation factors:

P Total UPS apparent power (VA) P Power demand for total battery (W)

V Total Float total voltage V Float voltage of 12V or 2V single cell

Pc Discharge power per cell (W/cell) Pb 12V battery discharge power (W/battery)

Pf Output power factor η Inverter efficiency

K Reliability coefficient (1.0, 1.25) Sn Number of battery string sections

Pn Battery group parallel number (1, 2, 3, 4) t Backup time

② Calculation steps:

Total battery demand power P = K * P Total * Pf/η

Calculate battery string number Sn = V Total / V Float

Single cell discharge power Pb = P / (Sn * Pn)

Discharge power per cell Pc = Pb / 6 Calculate Pb or Pc when Pn = 1, 2, 3, 4

③ Check the selection table:

Select the battery specification that meets the performance requirements at the corresponding backup time and cut-off voltage in the 12V battery constant power discharge data table.

④ Calculation example:

Demand is 100KW, backup time is 2 hours.

Total battery demand power P = 1 * 100KW * 1/0.96 = 104.16KW

Battery string number Sn is generally 28/30/32/36, selecting 32 series-connected battery packs

When Pn is 1,

Single cell discharge power Pb = 104.16KW / (32 * 1) = 3255W

Discharge power per cell Pc = 3255/6 = 542.5W

When Pn is 2,

Single cell discharge power Pb = 104.16KW / (32 * 2) = 1627.5W

Discharge power per cell Pc = 1627.5/6 = 271.25W

When Pn is 3,

Single cell discharge power Pb = 104.16KW / (32 * 3) = 1085W

Discharge power per cell Pc = 1085/6 = 180W

When Pn is 4,

Single cell discharge power Pb = 104.16KW / (32 * 4) = 813.75W

Discharge power per cell Pc = 813.75/6 = 135.625W

Based on the discharge power per cell Pc at Pn = 4, with a parameter of 135.625W, confirm that the configuration of the battery pack for a load of 100KW with a backup time of 2 hours is 4 groups, each with 32 12V200AH rechargeable batteries, for a total of 128 batteries.

Note:

1. This method is suitable for calculating a maximum of 100KW for a 2-hour delayed scenario, 200KW for a 1-hour delayed scenario, 300KW for a 30-minute delayed scenario, 400KW for a 20-minute delayed scenario, 500KW for a 15-minute delayed scenario, and 600KW for a 10-minute delayed scenario.

2. Default Pn = 6, and the selected rechargeable battery is a 12V valve-regulated sealed lead-acid battery; constant power discharge data table reflection; models include 12V17AH/24AH/38AH/65AH/100AH/150AH/200AH/250AH.

3. The default battery string number Sn is 32, subject to the actual setting of the UPS power host, generally adjustable in multiples of 28/30/32/34/36/40/48/50. Of course, the larger the Sn, the relatively smaller the discharge power per cell Pc.

4. The default battery group parallel numbers Pn are 1/2/3/4, and under normal conditions, the maximum number of battery groups is 4. After the UPS power host is set, the charging efficiency meets normal use after the battery group is placed.