Can I go for a 120 AH battery then?Well looking at the load, your load is indeed less, all your equipments are DC powered equpiments and they require very less electricity consumption.
The size of the battery is determines the duration it will work. SO if you would be using 165AH battery, then it would last longer than a lower AH battery
A small definition what AH means is the Amphere hours. If you draw one ampere from this battery, it will work for 165 hours before discharging completely. If your load draws 2 amperes than your battery will last (165/2) = 82.5 hours
Usully 165 OR 150AH are standard batteries that are used. However, the next in line is 120AH. If you load is less than you should probably go for 120AH battery. But dont go for lower than 120AH ones. They are very small and i have never seen these smaller batteries with UPS.
Also, every size battery has a required charging amperes and they are mentioned here
http://www.exide.com.pk/Products/Automotive/Range/specifications_of_Exide_Automotive_Batteries.pdf
Now check with your inverter how much charging amperes does it provide (i tried googling but didnt help)
If you oversize the battery than your inverter has chances of being damaged, due to longer charging times
If you undersize the battery than your battery life is compromised as higher charging current will degrade battery life.
So its better that you select battery that is neither too big and neither to small.
120 to 165AH should be good. 165 is almost same as 150 so dont bother in between these two
My inverter has a 15A and 20A charging option.
I read in the users manual that 15A charges slower and prolongs the overall life of the battery.
20A charges faster and will reduce the life of the battery in the long run.
So if I buy a 120 AH battery, can I use it on 20A charging mode?
Sent from my SM-G928C