Power Electronics / Power Management


UPS battery configuration made easy

28 August 2019 Power Electronics / Power Management

Determining the UPS (uninterruptible power supply) battery configuration using a formula can be quite complicated and, since many users are not very familiar with it, a more simplified method can be used to speed up the process and thereby save time.

This is typically done in the pre-planning phase before designing the practical application solution. The battery configuration can be quickly and simply calculated based on the UPS output load and the required backup time. The formula is as follows:Required battery capacity (Ah) = UPS capacity (kVA) x 109 (Ah/cell) + kVA + number of battery blocks per group

Example 1

As an example, consider a 130 V d.c. system of 120 kVA operating a UPS with 32 cells in series per bank, and requiring a backup time of 60 minutes. The required battery capacity is:

120 kVA x 109 Ah (cell/kVA) = 13 080 Ah (total requirement)

13 080 Ah / 32≈409 Ah

Therefore, if using a 12 V, 100 Ah battery bank x 4, there is a choice between using 32 cells per group, in which case the actual backup time will be less than 60 minutes, or 33 cells per group, resulting in a backup time of slightly more than 60 minutes.

If the required backup time is 30 minutes, then:

120 x 109 = 13 080 Ah

13 080 / 32≈409 Ah (for 60 minutes)

409 / 2≈205 Ah

However, since the discharge power and discharge time of the battery are not linear, simply dividing by 2 is incorrect; rather, a modified coefficient must be used (see Table 1). Therefore, in this case, 205 x 1,23≈252 Ah, so one option could be 4 banks (32 cell/bank) of 12 V, 65 Ah battery.

If the backup time requirement is 20 minutes, then:

120 x 109 = 13 080 Ah

13 080 / 32≈409 Ah (for 60 minutes)

409 / 3≈136 Ah

136 x 1,41 (modified coefficient) 192 Ah

Therefore, one option could be 3 banks (32 cells/bank) of 12 V, 65 Ah batteries.

Example 2

Consider a 126 Ah/cell/kVA system, of 120 kVA UPS with 32 cells per bank. If the required backup time is more than one hour you also need to consider the modified coefficient in the calculation (see Table 2).

If the required backup time is 3 hours, then:

126 x 120 = 15 120 Ah

15 120 / 32≈472 Ah

472 x 3 = 1 416 Ah (for 3 hours)

Then divide it by a modified coefficient as 1 416 / 1,25≈1 133 Ah

The option of 4 banks of 12 V, 300 Ah batteries can therefore be selected.

According to the principle of energy conservation, the above method is the same for three-phase/single-phase or single-phase/single-phase UPS. Generally, high-power UPS systems are equipped with 32 batteries per battery pack and the number of parallel batteries should not exceed 4 so as not to affect the current sharing and charging effect of the battery pack.

However, the above is a simplified method that is only a rough calculation where the result which is not completely accurate. To obtain a more accurate result, one will also need to consider the parameters of the equipment, the requirements of the application, the power grid condition and the power conversion efficiency.

For more information contact Forbatt SA, +27 11 469 3598, [email protected], www.forbatt.co/index.php



Credit(s)



Share this article:
Share via emailShare via LinkedInPrint this page

Further reading:

Powering Innovation eBook: Changing what’s possible
Power Electronics / Power Management
This exclusive read, entitled ‘Changing what’s Possible,’ delves into how power dense Vicor modules enable many world-changing innovations across various sectors.

Read more...
16-channel multicell battery monitor
Altron Arrow Power Electronics / Power Management
The ADBMS6830B is a multicell battery stack monitor that measures up to 16 series-connected battery cells with a lifetime total measurement error of less than 2 mV.

Read more...
Reliable redundancy with the Mibbo M3DN Series
Conical Technologies Power Electronics / Power Management
Designed for use with two parallel-connected power supplies, the M3DN Series allows for true redundancy, making it ideal for mission-critical applications.

Read more...
Automotive power-over-coax inductor
RS South Africa Power Electronics / Power Management
TDK has launched the ADL8030VA, a high-performance inductor designed specifically for power-over-coaxial applications.

Read more...
Rugged PSU for challenging conditions
Conical Technologies Power Electronics / Power Management
Built for rugged reliability, the Mibbo MFC Series delivers stable, efficient power in environments where moisture, dust, and temperature extremes are everyday challenges.

Read more...
Enhance SiC device efficiency using merged-pin Schottky diodes
NuVision Electronics Editor's Choice Power Electronics / Power Management
Silicon carbide (SiC) has advantages over silicon (Si) that make it particularly suitable for Schottky diodes in applications such as fast battery chargers, photovoltaic (PV) battery converters, and traction inverters.

Read more...
15 W power module with wide input range
Brabek Power Electronics / Power Management
RECOM’s miniature power modules provide 15 W output and operate over a wide input range of 18-264 V AC or 18-375 V DC.

Read more...
Industrial-grade DIN rail PSU
Conical Technologies Power Electronics / Power Management
The Mibbo MTR960W is a reliable and cost-effective PSU option that delivers a solid 960 W of output power at 24?or 48 V DC.

Read more...
Energy harvesting and Matter for smarter homes
RF Design Power Electronics / Power Management
Qorvo’s collaboration with e-peas on the Matter Enabled Light Switch marks another significant step in advancing Matter adoption across the IoT industry.

Read more...
3-terminal filters for automotive applications
RS South Africa Power Electronics / Power Management
TDK has expanded its YFF series of 3-terminal filters for automotive applications to include higher voltages up to 35 V and higher capacitances up to 4,7 µF.

Read more...









While every effort has been made to ensure the accuracy of the information contained herein, the publisher and its agents cannot be held responsible for any errors contained, or any loss incurred as a result. Articles published do not necessarily reflect the views of the publishers. The editor reserves the right to alter or cut copy. Articles submitted are deemed to have been cleared for publication. Advertisements and company contact details are published as provided by the advertiser. Technews Publishing (Pty) Ltd cannot be held responsible for the accuracy or veracity of supplied material.




© Technews Publishing (Pty) Ltd | All Rights Reserved