Why UPS Not Working After Power Cut? – Troubleshooting Guide

An uninterruptible power supply (UPS) is always ready to provide backup power to your devices when a power cut happens. However, some UPS units can stop working even after the power cut is over.

When your UPS stops working after a power cut ends, it’s likely because there is an incoming power issue. Check that your circuit breakers have not tripped, your fuses have not blown, and that your wall socket is still working. Besides that, the cause could be a post-blackout power surge, an improper UPS restart, or a fault in the UPS or its battery.

The following sections will help you understand why your UPS might not work after a blackout, even though it successfully protected your devices before that.

Why Is My UPS Not Working After A Power Outage?

When a power outage ends, and everything comes back on again, your UPS should also resume its normal operations. A working UPS will reset itself and begin recharging its backup batteries.

But what happens if the UPS no longer works after power is restored? Here are the most likely reasons for that and what you can do to fix them.

Incoming Power Supply Issue

What it is: When you notice that your UPS isn’t working after a power outage, the first troubleshooting step you should take is to check its incoming power supply.

Remember: the UPS will drain its battery during a power outage. If the outage goes on for too long, the UPS will lose all its power and must recharge when power is restored.

The UPS won’t turn on unless there is incoming power which might be affected by a faulty wall socket, a tripped circuit breaker, or a blown fuse.

What happens: During power disruptions like blackouts or brownouts, the electricity supply to your building will likely be unstable. That can cause several problems.

Firstly, it can cause a circuit breaker to trip. That could be the circuit breaker in your building’s main electrical box or the built-in circuit breaker in your UPS unit.

Besides that, unstable electrical currents (which include power surges) can blow fuses in the UPS or your wall socket (if it has one).

Any of the above will prevent power from flowing to your UPS after a power cut, causing it not to work as it should.

How to fix it: Firstly, check for any tripped circuit breakers and reset them if necessary. Remember: there’s a circuit breaker at the main electrical box for your wall socket and another built into your UPS unit.

Next, check that the wall socket is still functioning. If it isn’t, you’ll have to plug your UPS into another working socket.

Read: How To Troubleshoot UPS Battery?

Power Surge After A Blackout

What it is: As you saw above, a power cut or blackout can lead to power surges. This is often overlooked by most people.

The power surge happens when the power cut ends and the electrical current is restored. The sudden flow of electrical current can include power surges that damage appliances and devices. 

What happens: When a power cut ends, and the electrical current resumes, the sudden surge could cause damage to your UPS or its electronic components. Power surges can cause things like the main control board to overheat, burn, and stop functioning.

As a result, your UPS stops working even after the power cut ends.

How to fix it: First and foremost, disconnect your UPS from the wall socket immediately. A UPS with damaged components is very dangerous if you leave it connected to an incoming power supply.

Next, all damaged components inside the UPS unit must be replaced. Doing it yourself can be challenging and dangerous, so it’s best to let a qualified technician do it for you.

Read: Why Ups (Battery Backup) Is Beeping Continuously?

Improper Restart

What it is: After the UPS does what it’s meant to do during a power cut, it will initiate a restart or reboot process. That will happen once the UPS senses that the power outage is over and its power supply has been restored.

The restart or reboot process for some UPS models can be somewhat like how many other electronic devices behave when you turn it on. 

It’ll take a few moments to complete, and some UPS models might even initiate a self-test to ensure that everything is functioning correctly.

Then, the UPS will perform its regular functions like recharging its battery. If there are any errors, the self-test feature will alert you by flashing indicator lights or displaying an error code (on some models).

What happens: Throughout this guide, you’ve seen that power restoration after a blackout isn’t always stable. For example, there can be voltage or current surges.

Unfortunately, that power can also fail to come back on all at once. Instead, the power might be unstable for a few moments, cutting off and returning several times.

That lack of stability after a power cut can confuse the UPS and prevent it from restarting normally. When that happens, the UPS will not work after the power cut.

How to fix it: One way to solve this issue is to disconnect the UPS from its wall socket and leave it alone for a few minutes. You can plug the UPS back into the wall socket when you’re confident that the power cut is over and your power supply has become stable.

Then, follow the manufacturer’s instructions for your UPS model to reset the device.

Read: How To Check UPS Battery Health?

UPS Or Its Battery Are Faulty

What it is: A UPS and its battery can suffer from faults. These could be from extensive wear after being in use for several years. Or, it could also be faults that develop after putting the UPS through too many discharge cycles.

Naturally, it’s also possible that the UPS was faulty even when you purchased it. 

What happens: Although less likely, it’s possible that your UPS or its backup battery was already faulty even before the power cut. The power cut could have essentially pushed the UPS over the edge and caused it to stop working.

How to fix it: Unfortunately, troubleshooting a faulty UPS or its battery can be challenging and dangerous. So, if you’re not sure how to do it, it’s always best to send it for servicing by a qualified technician.

A faulty UPS still within its warranty period will usually be fixed free of charge. But, of course, that will depend on the warranty terms that apply to your UPS brand and model, as well as the seller you purchased it from.

Read: Can A UPS Last For 3 Hours?

Frequently Asked Questions (FAQs)

Here are a few more commonly asked questions to help you understand your UPS and how it works:

How Does A UPS Work When The Power Goes Out?

The electronic components in your UPS will sense when the power goes out. That will trigger the UPS to start discharging its battery power to keep your critical devices running for a few moments, so you can shut them down safely.

Should I Turn Off UPS During Power Outage?

Yes, you should turn off and disconnect your UPS from the wall socket during a power outage. That’s because the power outage could cause current and voltage surges when power is restored. Plus, the power supply could be unstable for a while after the end of a power cut.

Read: What Happens When UPS Battery Fails?

Should I Unplug UPS At Night?

No, you shouldn’t unplug a UPS at night. The purpose of a UPS is to instantly provide backup power during a power outage. Unfortunately, a blackout like that could occur at night, leaving your critical devices without power.

What Happens When UPS Runs Out Of Battery?

When a UPS runs out of battery, it will shut itself off. Unfortunately, that also means it’ll stop providing backup power to your critical devices.

How Long Do UPS Last During Power Outage?

A UPS typically lasts for 15-30 minutes during a power outage. However, that duration will depend on two things. Firstly, it depends on the battery capacity in your UPS. Secondly, it depends on how many devices drain power from the UPS.