Apc constant alarm both on battery and mains

check owner manule

Open it up and check the fuse. or your UPS may have a pop out fuse that may need to be reset

Continuous Beeping (theamber On Battery LED will be illuminated)
This alarm indicates that the UPS has reached aLow Battery condition and will soon shutdown. The UPS can only operate onbattery for a limited amount of time. In order to protect the unit's batteriesfrom discharging too much, the UPS will shutdown and turn off its output. Towarn you that the unit will soon shutdown, the UPS will sound this alarm 2minutes before actual shutdown. With optional Powerchute Plus software, 2minutes can be changed to 5, 7, or 10 minutes to give you more of a warning ofimpending shutdown. If you hear this tone, you should immediately gracefullyshutdown your operating system to prevent data loss or corruption.
Note:This graceful shutdown will occur automatically if Powerchute PLUS software isbeing used.

Constant, Solid Tone (the red Overload LEDwill be illuminated)
This alarm indicates that the UPS has detectedan Overload condition. If this alarm is sounded, try removing non-essentialequipment. The alarm will remain until the load is reduced. To determine ifyour UPS is capable of handling the equipment you want to protect, visit APC'sSizing Guide at www.apcc.com/sizing.

Continuous Beeps for One Minute; RepeatedEvery 5 Hours (Replace Battery LED will be illuminated)
This alarm indicates that the UPS has failed itsSelf-Test of the battery. The unit will continue to sound this alarm until theunit passes the test. Try to let the unit charge for a few hours and thenperform another Self-Test (Press and hold the on/off button until the second'chirp', then release). If it fails and the unit is still in-warranty (twoyears from date of purchase), then contact APC. If the unit fails and its outof warranty, then order a replacement battey cartridge through your reseller,distributor, or from APC's web site.

If the device was still under warranty, you should call APC support and ask to send it in for repairs or replacement. Just keep politely asking, and ask to talk to their superior whenever they say it isn't possible and eventually you will get an RMA ticket/number.
If the device is not under warranty, you might be able to convince APC to service the device for a fee.

It sounds like you need a new battery. If the APC is more than 3 years old, that is likely the problem. You can get a new battery from http://www.batteryinternational.com/apc-backups-es-be500u-ups-battery-ups-batteries-f2.html

restart the ups by to turning off your ups and main source. and turn it on again. anybe the battery u purchase is deflected. change the new battery & test again. i suggest to replace other type of battery like neuton power, chloride powersafe as this type is much reliable and cost saving. the cost of the the problem if still occur it could the setting of the UPS that it to configue.. ask the vendor to check your ups

must be either low main power or cable damaged or not inserted properly

need to checked by expert

try to change with new battery and test. if it does't work it could be the hardware is malfuntion. but that the lastsolution to think, what are the indicator light is stated? can u descibe more detail on the ups. so i can able to asst u?

i think by replacing the battery has not been the solution to the problem

u need to check the battery charging voltage when turned ON with main electricity, if no voltage present from charger, there is no question of battery getting charged and also once the battery is down with charge it may not re charge hence the indicator and alarm.
recomended to nearest service centre