Ok, i know that this might be a late reply.
Now 1400 VA provides you about 900 watts to 1000 watts maximum output. Please specify the efficiency of the UPS at full load in battery mode.
Lets assume your Inverter has 80% efficiency and the logic goes like this. The inverter can convert 80% of the DC back up available.
Volts * amps = watts
Now if you are going to use 1000 watts, then lets derive the amps required from your battery
1000 watts/12 volts = 83 Amps. So your battery can provide back up of about close to an hour. Since the UPS has 80% efficiency subtract 20% from your total battery capacity.
If you go for 100 AH battery and combined with 80% efficiency, you will get a back up of upto 80 AH.
Now if you need 1 hour on full load you need minimum 100 AH.
Now keep adding amps for more back up time.
With regards to the selection of battery types
1. First choice Tubular batteries - Long lasting, less maintanence
2. SMF batteries - Complete no for Inverters, since Inverters are always good with flate plate batteries. SMF die soon with inverters, but lasts long with UPS.
3. Automotive batteries - Cheap, but does not like deep discharge. Complete "NO" for your requirement. But personaly speaking, people have been using automotive batteries for back up since ages. All these inverter batteries and gimmicks came into picture in the recent past
I have seen people using automotive batteries which lost its cranking power for back up for years.
Now it all depends on your personal choice.
If you are a person who would deep discharge your batteries go for Tubular or other inverter batteries.
Guys my personal experience is that, now a days even automotive batteries have a thicker lead plates. They say inverter batteries have thicker plates and it does not mean the plates are measured in inches. I have personally taken a look at the lead plates from inverter batteries and its about less than 2 mm thickness.
Surprisingly few of the automotive batteries has also the same thickness, since the power requirement of automobiles have changed now a days. You need to have the security system running, power windows, audio system, fans...
I guess normal inverter batteries and good automobile batteries are the same. Its just my personal thought.
Thanks for having the patience to read through this whole paragraph. I guess this helps the person who raised the query.
