A UPS can provide power for a few minutes up to several hours, depending on several factors. The capacity of the UPS is the main factor determining how long it lasts. A UPS with a larger battery capacity will last longer.
The number of devices connected to a UPS also affects the runtime. Environmental factors like temperature and humidity levels also affect the UPS power supply.
We will explore the mechanisms of a UPS to reveal how it works and the factors affecting the duration of the power supply.
Components of A UPS
An Uninterruptible Power Supply (UPS) unit provides electrical power during a power outage. Additionally, this device can supply stable electricity to all connected devices if the main power fluctuates, and that’s possible only if its components are functional.
A UPS has three main components working together. Each component serves a specific function, and together, they provide clean power to the connected devices.
Battery
Usually, you connect the UPS to a wall outlet. The UPS converts the alternating current (AC) from the wall outlet to direct current (DC) and stores the power inside its battery.
If the main power supply fails, the UPS converts the battery energy back to AC to power all connected devices.
Inverter
The inverter is a crucial component inside a UPS. It converts the DC battery power to AC power, which most electrical appliances consume. In addition to DC-AC power conversion, the inverter protects the connected devices against mains electrical surges and spikes.
Charger
The charger converts the AC power from the wall outlet to DC power stored in the UPS battery pack. It’s important to remember that Lithium-ion batteries used in many UPS units can only store direct current (DC) power.
Many people might confuse the role of the charger with that of the inverter. While these two components convert power, the charger converts power from the mains to DC electricity stored in the UPS device.
On the other hand, the inverter converts the DC power in the UPS to AC power to power up all connected devices.
How The UPS Provides Backup Power
The UPS relies on two mechanisms to provide electrical power during an emergency:
Battery Storage
To provide backup power, the UPS stores electricity from the wall outlet in its battery. Each UPS has an internal battery rated in ampere-hours (Ah). The battery capacity determines how much energy the UPS can store.
A UPS with an internal battery rated at 100Ah can provide up to 1,200Wh of energy. The higher the battery capacity rating, the more energy the UPS can provide during a power outage.
Power Conversion
The UPS has an inverter that converts the DC power stored in the battery to AC power. The inverter regulates the output voltage and ensures it remains stable even if the battery produces fluctuating voltage.
Moreover, the inverter maintains the power output frequency to ensure the connected devices consume clean electricity with perfect sine waves. This makes a UPS ideal for powering sensitive electronics like smartphones and TVs.
Types of UPS Systems
If you’re in the market for a UPS unit to provide backup power during a blackout, you have three types of UPS systems to choose from:
Standby UPS
A standby UPS system is the most basic. Consumer electronics connected to this UPS will experience a brief power interruption as the UPS switches to its battery power. Under normal conditions, the UPS can offer surge protection.
Line-Interactive UPS
This UPS type provides backup power and regulates the voltage output with its autotransformer. It also protects your devices against power surges. However, it also experiences a brief power interruption as the autotransformer switches to the battery power.
Online UPS
While it’s expensive and consumes more power, an online UPS switches to backup power seamlessly without power interruptions, making it best for powering servers and medical equipment in an emergency.
Factors Affecting UPS Runtime
The size of the UPS battery and the number of connected devices affect the UPS runtime.
Battery Capacity
The battery capacity is how much electrical energy a battery can store. Each UPS has an internal battery with a specific capacity.
Amp-Hour Rating
Battery capacity is measured in amp-hours (Ah). A UPS with a 100Ah battery can supply 100 amps of current for 1 hour or 20 amps for 5 hours.
Voltage
The voltage (V) determines how powerful the UPS is in powering electronics. A UPS with a higher voltage output can provide more electrical power to support more devices for extended periods.
Power Load
The number of electronics connected to the UPS affects its runtime. The more devices you connect, the shorter the runtime.
Wattage of Connected Devices
A watt is the electrical power consumed by a connected device. You’ll add the Watts of the connected devices to find the total Wattage of the connected devices. More devices result in increased power consumption and a shorter runtime.
Power Consumption Variability
If the connected devices draw power from the UPS steadily over time, the UPS runtime is easy to predict. However, some electronics consume more power at certain stages, like during startup and when loading some applications. Such electronics will reduce the UPS runtime.
Age of the UPS Battery
As time passes, your UPS battery degrades, especially with each completed charging cycle. The battery then holds less energy. You’ll expect your battery to hold less energy 3 years after using your UPS as a power backup.
Degradation Over Time
The UPS battery has to charge and provide the stored energy in emergencies. There are chemical reactions as the battery charges and discharges. These reactions wear out some battery’s internal components resulting in a weaker battery over time.
Maintenance and Replacement
Battery degradation is the main cause of declining UPS power over time. Battery maintenance and replacement can restore a UPS performance. Battery maintenance looks out for corrosion and loose connectors and repairs such problems.
At the same time, battery maintenance can repair leaking electrolytes. If the battery is worn out beyond repair, fitting a new battery can restore your UPS performance.
Estimating UPS Runtime
You can estimate a UPS runtime by reading the information specified by the manufacturer. To obtain a more accurate result, you can also do load testing.
Manufacturer Specifications
UPS manufacturer usually lists information on the UPS to help you determine how long the UPS will last during a power outage:
- Battery capacity
- UPS Voltage output
- Load Capacity
- Power Efficiency
Load Testing
You can also do a load test to determine the UPS runtime. A load bank device will help you do a load test on the UPS. The load bank will draw energy from the UPS system, and you can monitor the battery discharge rate and voltage output.
Calculating Runtime Based on Load
You can also do calculations to estimate the UPS runtime. A good formula goes a long way in UPS runtime estimation.
Formula for Estimation
Some UPSs rate their battery capacity in Watt-Hours. If your UPS battery rating is in amp-hours (Ah), convert it to Wh. Amp-hours refer to the charge inside the battery, while Watt-hours refer to the power output rating.
Add the wattage of all devices connected to your UPS system. Then divide the UPS Watt-hour (Wh) rating by the total wattage of the devices to get the runtime in hours.
Examples of Scenarios
For example, if your UPS battery is rated 1,200Wh and you’ve connected devices with a total wattage of 600 Watts, you divide 1,200 by 600, and you get the runtime in hours.
1,200Wh ⁄ 600Wh = 2 hours.
You can multiply the battery charge capacity in amp-hour (Ah) by the battery voltage (V) to get the Watt-hour power output. For example, a 100 Ah battery with a 12V output has a 1,200-watt-hour battery power output.
Expected Runtime in Practical Situations
A UPS runtime depends on the appliances or electronics you want to power in your home office or business establishment.
Home Office
A home office has essential devices like computers, internet routers, printers, and scanners. The devices in a typical home office consume no more than 200 Watts of power. If the devices are connected to a 1,200-watt UPS, they can be powered for 20 hours without the main power supply.
Data Center
Servers, network switches, and routers are the main devices that need power. These devices can consume 2,500 Watts of power. Therefore, a more powerful UPS system is required to keep the data center operational.
Proper UPS Maintenance
Maintaining a UPS prolongs the battery life and improves UPS performance. You will maintain your UPS by doing the following:
Regular Testing
You will run regular tests in simulated power outages to check if the UPS switches to battery power as expected.
Battery Replacement Schedule
If there’s a problem with backup power switching, you’ll schedule the UPS for battery maintenance or replacement. A technician will remove any dust and rust inside the UPS components.
Avoid Overloading
Overloading a UPS system causes overheating because the components work harder to meet the power supply demand. However, heat speeds battery wear and breakdown. Avoiding overloading will prolong the UPS lifespan.
Use of External Battery Packs
External battery packs can supplement UPS backup power and extend the runtime of mission-critical devices. The extra power supplied by the external battery pack eases stress off a UPS system, thereby prolonging the UPS battery power supply.
Conclusion
A UPS is a critical power backup device that any home office or business requires to maintain normal operations in a power outage. However, the UPS can only provide power for a limited time. Supplementing UPS power with external battery packs can extend the runtime of mission-critical devices like servers.
You want to avoid overloading the UPS to protect the unit against overheating and imminent damage. You also want to subject your UPS system to frequent maintenance and repairs to ensure optimal performance during power outages.
