I guess faulty battery? But it's quite new......Will change the battery from one of the working UPS (same brand model) to see if it's indeed the battery's problem. Otherwise I don't know where I can pay for 400 bucks for another 800VA UPS at this time of the year. Don't want to waste my time on return it to that stupid store, they did not bother with the first time, don't think I will get any service now.
This UPS is mainly for the switch and wireless router which connected my dad's home office to the internet.