Found the answer
Hello. I found the answer to the continuous beep error of PowerWise L600. I recently found this UPS and upon powering up i got the continuous error beep. No lights turned on. I opened it and found out the batteries were completely dead. I replaced them (has 2 pcs 12V/7Ah and are stored in a very hard-to-reach place...had to take apart all components) and the UPS came to life. Seems it has a set of tests before turning on including measuring battery voltage and surge. On short the solution is a new battery pack replacement. Enjoy this super UPS.