AH is Ampere hours...you get 180 AH batteries also and if you go for more than 750 VA UPS,you will have 2 batteries of 150 or 180 AH ,24 V (12+12)
A computer with 14" monitor consumes about 40 AH per hour so with 150 AH battery you will get a back up of about 4 hrs for 1 computer.If using a laptop it will work for 6 hrs approximately.
The above was told to me when I selected my UPS and batteries.
Smart_trade
UPS/INVERTER/BATTERY BUYING GUIDE
How to select the Inverter?
Step 1: Calculate the total power you are connecting,
W.
Step 2: Find the Power Factor of Inverter,
pf. Check with the inverter for pf or use 0.8 .
Step 3: Calculate the
VA connecting by the equation,
VA =
W/
pf.
Step 4: Buy a UPS which has a rating of above the
VA.
How to select a battery?
Step 1: Decide how many hours backup time needed (All devices connected at a time), BH.
Step 2: Decide which battery you are going to buy, 12
V or 24
V. For this you need to check which(12V or 24V) battery the above selected Inverter supports.
Step 3: Calculate AH by the equation,
AH =
W*
BH/
V .
Step 4: Buy a battery having the above
AH and
V ratings. It will be a good idea to have a bit higher AH battery than the calculated one.
Provided the battery C-rating is C/10 (or .1C), normally we are getting C/10 batteries for inverters. Will add more about it later. The above is a theoretical calculation and the actual backup time may be little lesser so try to buy a battery having a bit more AH rating.
Thank you,
TFL.