Dear Zameer,
Raising the battery amps is not only the solution.
First of all you have to calculate your power need. As you describe in first post 3 fan, 3tubelights, 2 routers. A rough calculation of your power what u need a
Power Rated = 1 KVA
Output volt = 220v
Input volt = 12v
The reason why I m saying this.
@ 1kva with input of 12v you required 84 Amps for 1 hr (Calculated UPS)
@ 2Kva with input of 12v you required 166 Amps for 1 hr (your UPS)
Secondly your UPS is imported. Most of imported UPS are not designed to use at longtime backup. they designe it just for transition time between wapda and generator.
So resulting for longtime smooth backup you need acurate UPS and Battery.