Difference between BESS and Online UPS


An online UPS and a battery energy storage system (BESS) provide backup power in a power outage, but they work differently.

Online UPS

An online UPS (uninterruptible power supply) is a type of UPS that provides continuous, uninterrupted power to connected devices. It uses a rectifier to convert incoming AC power to DC power stored in a battery. The battery is then used to power an inverter, which converts the DC power back to AC power. This means that the connected devices always receive power from the Inverter, and the battery is always working.https://en.wikipedia.org/wiki/Uninterruptible_power_supply

Battery Energy Storage System

A battery energy storage system (BESS) is a system that stores energy in batteries. This energy can then be used to provide backup power in the event of a power outage, or it can also store energy from solar power if it has the provision. The BESS is the latest technology developed for backup purposes, and it has isolation power in case the transformer technology makes it.

Comparison between Online UPS and BESS

High Frequency-based Online UPS is made through the circuitry where triple conversion technology wastes a lot of energy, and the battery constantly remains in the picture, reducing the battery life. At the same time, the BESS passes the power through the isolation transformer, which gives the isolation to the Computers and transfers to the battery mode when the Power outage happens.https://suvastika.com/bess-battery-energy-storage-solutions/

Voltage Range: In the Online UPS, the Input voltage range is 180 V to 265 Volts, a very small range for countries with high power fluctuations. The output Voltage is always 220V+/—1%. This does not make any sense in today s world as most IT products like computers and Wi-Fi routers come with 110 V to 260 V. Still, we are giving 220 to the computer and using online UPS, which was the requirement of computers made initially, which were designed on transformer-based technology so needed 220V. The major challenge is the Input voltage range is 180 to 260 volts which is the major challenge for online UPS. The moment voltage goes below 180V, the battery will come into the picture, so when the power outage happens, the battery is already consumed, so there is no backup time in case of power failure. So in the case of BESS, the voltage range is wide, like 140 Volts to 265 Volts which is the safer limit for the IT loads and switches the power to battery mode. If this voltage range is violated

Charging time The charging time for online UPS is at least 8 hours to charge the battery, and for Online UPS battery keeps on discharging as well to keep the voltage to 220Volts. So the battery is hardly charged fully. But in the case of BESS, the battery is charged in 2 to 3 hours, and BESS is ready to Power the computers and IT equipment always.

Backup time In the case of Online UPS, the backup time will always be lesser than the BESS as the Lithium battery is charged faster than the SMF battery.

Switching time In the case of online UPS, there is zero switching time which keeps the computers and IT peripherals running in case of power failures. Our BESS also has a switch over time of fewer than five milliseconds which cant switch the computers, and IT loads switch in case of power failure.

Life of the battery In the case of Online UPS, the battery life is generally 12 to 18 months, reducing the backup time, and the user changes it when it gives 2 to 5 minutes of backup time. The Lithium battery’s life is ten years, and the warranty provided is three years minimum.

IOT-based BESS The BESS can monitor and control it through Bluetooth and Wi-Fi-based mobile applications, whereas the Online UPS works on old SNMP technology.


The table below summarizes the key differences between online UPS and battery energy storage systems:

FeatureOnline UPSBattery Energy Storage System
Continuous powerYesyes
PriceMore expensiveLess expensive
Protection against power surgesyesyes
ApplicationsCritical applications, such as data centres or hospitals Critical applications, such as data centres or hospitals

Which one is right for you?

The best choice for you will depend on your specific needs. BESS is the best choice if you need continuous, uninterrupted power for critical applications, voltage variations are in your area, and you need more backup time.

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