I guess this section is the easiest part in this Beginner’s Guide, because almost all of us know ‘What is a UPS?’ But still I just want to give an overview of it.

From today we are going to see the external components of the computer. The first one in this list is UPS; the expansion is uninterrupted power supply.

What is a UPS?

In our terms, it means, show me the UPS.


It’s normally placed aside your cabinet or CPU that looks like a mini CPU, because of its size.

A UPS generally have 3 to 4 power sockets at the back that provide AC power supply from your mains to your CPU, when main power supply is available. When mains goes off or fail, UPS comes into action to give power to your computer, from its battery.

Generally the UPS, which we use for our PC, is of quasi sine wave nature, whereas the power supply from our mains is pure sine wave. But all our electronic and electric devices that we use in our home are designed to be operated on pure sine wave.

Then, why computer UPS are of quasi sine wave nature? Do you know?

It’s because of cost cutting purposes. Our 650 VA pure sine wave home UPS costs around 4500 Rs, but a 600 VA computer UPS along with a backup battery costs just 1700 Rs.

So if you operate the PC from such UPS, while main power supply is not available, the efficiency of SMPS will get reduced considerably. Not only that, the electric components inside the SMPS may also get damaged, if you use such quasi sine wave based UPS in battery mode for a prolonged time.

But how?

As I have said in Day 18 – What is a PSU?, if the SMPS is less efficient, then more power is wasted in the form of heat, which unnecessarily heats the precious components inside the PSU, resulting in shorter life span.

So use your computer UPS, just to save your work and shut down your PC or just to hibernate it. Alternatively you may use your pure sine wave home UPS for PCs. But remember, you can use them only if you have UPS mode in your pure sine wave home UPS.

Why we need UPS?

We know that the data or content stored in RAM is processed by processor and again the results are stored back in RAM, before moving it to HDD. So if our mains go off before saving our work in HDD, we may lose our entire work, as the content stored in RAM will go off, when the power given to it is stopped.

That’s why we need a UPS. It switches to battery mode, at once, when power goes off.

Why PC UPS batteries have shorter life span?

There are many reasons for this issue, so let me list out some of them.

1.     Use of non-tubular batteries in PC UPS

2.     Faster and improper charging techniques in low cost UPS

3.     Faster discharging of battery than the maximum limit allowed

So if you want a longer battery backup, go for a tubular battery and a pure sine wave UPS, else use your PC UPS, but only for short span of time i.e. in minutes.