The battery backup time in hours can be calculated using following formula:

Backup Time = Battery AH x 12V x N x Efficiency of Battery / Load in Watts

where,

Battery AH = Ampere Hour Capacity of Battery

N = Number of 12 V Batteries needed

Efficiency of Battery = Generally it is 0.8, which is the max. power factor of home standard

i just put these value for 200 ah 24 v ups system

& 50 ah 4 battery 48v system is back time is same

Backup Time = Battery AH x 12V x N x Efficiency of Battery / Load in Watts

=50*48*4*.8/1000=7.68 hour

Backup Time = Battery AH x 12V x N x Efficiency of Battery / Load in Watts

=200*24*2*.8/1000=7.68 hour

is it right calc ?????????

which is best system and why??