I have a APC Back UPS, model UPS ES 500.
Today when I was turning on my PC, suddenly after flashing yellow light ( which is normal ) it started fashing red-light ( instead of green light ) and was beeping violently. After 3 to 4 trials it finally came back to normal. My question is, what was this problem ? Why did it happen ? Also, recently we are have sudden voltage fluctuations in our Apartment, could this fluctuations trigger this problem ?