Both battery backup and UPS can provide power to your critical equipment such as：pc，severs，data center infrastructure during a power outage.  However，there is still some difference between a battery backup and an uninterruptible power supply system.

UPS definition:

UPS is short for Uninterruptible Power Supply. UPS usually works with the battery and has a low battery alarm.  In addition to providing uninterrupted power to your critical equipment during power outages or brownouts, it also protects your equipment from surges/spike/line noise protection like surge protectors and it will supply a stable output voltage to ensure that the equipment works reliably. 

Therefore, UPS is more expensive and usually recommended for more sensitive and mission-critical equipment such as a server, data center of the financial industry, medical treatment industry, and transportation industry.  

Battery backup definition:

Backup battery powers the system when the main power supply is not available and it allows you to save the work while also giving the ability to shut down a computer properly until the electricity comes back on in a steady manner. Spare batteries range from small single cells to large battery room facilities to power uninterruptible power systems in large data centers.

Battery backup solutions are recommended for protecting your computers and other equipment since the investment in these devices is typically lower, as is the cost of battery backup. The length of time your device will stay depends on the battery capacity and the power consumed during a power outage.

In short, the uninterruptible power supply is a backup battery but has a higher protection rate, and the backup battery is only a backup power supply.

Learn more:why do you need a UPS?