Small Uninterruptible power supply (UPS), suitable for single PC or MAC. This unit will run a single computer in the event of a power cut (brown out) and ‘condition’ the mains supply to protect from a ‘ noisy mains supply’. It will give sufficient time to shut down and save work If power is off for prolonged period.
The rechargeable battery should last many years and can easily be replaced, from suppliers such as Tanya batteries for less than £20 delivered. ( Yuasa / Power Sonic).
The output as with most budget UPS is Pseudo Sinewave so not recommended for inductive loads such as drills.
Can provide power for a limited time if the mains fail.
BUT it smells all the time, possibly battery acid. I have thrown the whole thing away as I could not be sure the smell was dangerous.