My apc back ups 700 does not swhich on

[PERLARIA]

Goodmorning,it's 5 years that my ups works fine,now it's came the time to change the battery:i checked the specifications and

i found the new economic battery.it 's worked fine for 8 weeks(the battery arrived empty,but it's possible to recharge it).so i resand back the battery and i recived a new one;i's empty as the first,and it's not possible to recharge it.so i ordered others 2 battery of different brands,and something strange was appened:once i connected the battery,a continuos beep started.so i pressed the reset bottom,i listened the click,i reconnected the battery,the battery connector and tha AC:the apc didn't swich on,and the continuos beep restarted.i disconnected the AC,but the beep stopped once i disconnected the battery and i tryed again to reset,but i don't listen to the click.the new battery were different in 2 points about the specifications:the initial current is 1,6 for both;tha AH were 7,2 for all the 3 batteries(the sellers said to me that they were irrivelant).thanks to all for your help.mauro bontempelli